Full text of "A practical treatise upon warming buildings by hot water and upon heat and heating appliances in general, with an enquiry respecting ventilation, the cause and action of draughts in chimneys or flues, and the laws relating to combustion"

LIBRARY

UNIVERSITY OF CALIFORNIA.

Deceived M^^L- * , i8g

Accession's No.& 1 / 1 . Class No.

3TS,

AD'

\TJLIC WORLD.

1EDALS

JTIONS.

KEITH'S PATENT BOILERS

The " CHALLENGE/' The "VIADUCT," The " PYTHON," Ac.,

FOR HOT-WATER HEATING,

Require no building work round them, are without rivals in efficiency and economy, and heat respectively from 50 feet

up to 20,000 feet of 4-inch pipe, or its equivalent.

KEITH'S PYTHON BOILER, as illustrated, and in its full size, has about 1000 square feet of effective heating

surface, heats 20,000 feet of 4-inch pipe, and is the most powerful and complete sectional ' special ' hot-water boiler in the

world. KEITH'S Boilers are in successful use by
the thousands in all parts of the world, and they
are almost exclusively used by Her Majesty's
Government at the HOME OFFICK, for the heating
work of the prisons throughout the United King-
dom, in preference to all others.

CS ENGRAVING "illustrates the most powerful form of Boiler that has yet been made for Hot-water
Circulation." EXTRACT from 'Hooo' on Warming by Hot Water, New Editions, 1891-1893.

PHENOMENAL REVOLUTION IN

PUBLIC BATHS AND WASH-HOUSES.

KEITH'S PATENTED SYSTEMS OF HEATING WATER,

For Swirnmin 01 Ponds, Slipper and other Baths, Wash-tubs, Laundries. &c., by direct and indirect hot-water circulation on entirely new lines,
have, within "the past year or two, and with the approval of Her Majesty's Local Government Board, been largely adopted by Municipal
Corporations and Commissioners of Public Baths and Wash-houses, in preference to all other Systems. KEITH'S Systems have been adopted
notably at the Putney, the Ilampstead, the Battersea, the East Dulwich, the Camberwell Green, the Caledonian Eoad, and the Hornsey Boad,
Islington, Public Baths and Wash-houses, London; and at the Leicester Corporation Baths, <fcc., &c., with unparalleled efficiency and economy.
At the Hampstead Public Baths. London, where there are 360,000 gallons of water in Swimming Baths alone to warm and to keep warm,
at the end of the first season a profit equivalent to 50 per cent, of the total income was realised, while the highest efficiency was secured, a
result, up to date, without parallel in the history of Public Baths. See Special Prospectus.

KEITH'S PATENT SYSTEM OF HEATING AND VENTILATING TURKISH BATHS BY STEAM.

KEITH'S PATENT HYDRAULIC RAMS & RAM-PUMPS,

SELF-ACTING FOB RAISING WATER.

The very highest efficiency, attainable in self-acting and
concussive Hydraulics, assured bv KEITH'S Earn Appliances.

KEITHS'S PATENT ORNAMENTAL
OPEN FIRE HOT-WATER APPARATUS,

KEITH'S PATENT AUTOMATIC RAM VALVE GEARS,

For enabling RAMS to stop and re-start without attendance, are
suitable for all possible conditions, and allow of large RAMS being
successfully worked from the tiniest stream, if necessary.

With enamelled Tile Front combine warmth,
cheerfulness, and ventilation, with efficiency,
economy, and perfect safety. Can be set any-
where.

KEITH'S PATENT "UNIVERSAL" RADIATORS,

FOR HOT-WATER HEATING AND VENTILATION.

PLAIN AND ORNAMENTAL. - ALL CAST IN ONE PIECE. - NO JOINTS TO LEAK. - NO METAL SCREENS REQUIRED.
Unrivalled combination of Compactness, Neatness, Efficiency, and Low Price.

Have p'pat, radiatiner surface, give
most efficient ventilation, can be
dusted behind and beneath, are
made in various sizes, and can be
universally applied.

MANY THOUSANDS OF "UNIVERSAL" RADIATORS ARE IN USE.

KEITH'S PATENT MINERAL OIL GAS WORKS, for Lighting Mansions, &c., in the Country,
Have been adopted by the Beard of Trade and Commissioners of Xorthern Lights at Ailsa Craig, Langness, &c.

JAMES KEITH, c E. CASSOC. M. INST. c. E.),

d5a0, l^ncaulic, Beating, Fentilating;, anD Consulting; (Engineer,

CONTRACTOR TO HER MAJESTY'S GOVERNMENT,

57 HOLBORN VIADUCT, LONDON, E.G., ALSO AT EDINBURGH AND ARBROATH.

NOTE. Keith's Boilers and their principles of construction are being extensively imitated in the United States.
The Boiler named the " Perfect " is no> being manufactured in America under JAMES KEITH'S AMERICAN " CHALLENGE "
PATENTS, which United States' PATENTS have been purchased by and assigned to the makers of the said " Perfect" toiler.

HARTLEY & SUGDEN, LTD.,

WROUGHT-IRON AND STEEL

WELDED & RIVETED BOILERS,

OF EVERY DESCRIPTION, FOR

HOT-WATER HEATING APPARATUS.

CORNISH "TRENTHAJVI" BOILER.

ELEVATION.

CROSS SECTION.

J1EW INDEPENDENT " DUCHESS" BOILER.

Registered No. 195501.

New Illustrated Catalogue on application.

PRACTICAL TREATISE

UPON

WARMING BUILDINGS

HOT WATER

Telegraphic Address

"DONBOWES, LONDON."

Telephone
No. 3199.

BROADWAY CHAMBERS,

WESTMINSTER, LONDON.

Sole Licensees & Manufacturers of Mr, Eogers Field's Patents

ROGERS FIELD'S

NEW 1889 PATENT" SELF-ACTING SIPHON,

For building into Brick or Concrete Chambers, for Flushing Town Sewers, and

SELF-ACTING GALVANIZED IRON FLUSHING CISTERN,

Fitted with Rogers Field's New "1889 Patent" Annular Siphon for House Drains.

PREVENTS
DANGEROUS

DEPOSITS
IN DRAINS.

PREVENTS THE
LIABILITY TO

THE EVIL
EFFECTS OF
SEWER GAS.

AUTOMATIC FLUSHING CHAMBER FOR CLEANSING TOWN SEWERS.

Bowes Scott & Western's Patent

SELF-CLEANSING TROUGH CLOSETS

And Kogers Field's PATENT FLUSHING OISTEENS for same.

Suitable for Factories, Schools, Barracks, Workhouses, &c. &c.
TROUGH URINALS on the same principle.

REGISTERED IMPROVED FLUSHING GREASE TRAP,

FOR USE IN CONJUNCTION WITH AN AUTOMATIC FLUSHING CISTERN.

For further Particulars and Prices apply to

BOWES SCOTT & WESTERN, BROADWAY CHAMBERS, WESTMINSTER, LONDON, S.W.

A PRACTICAL TREATISE

UPON

WARMING BUILDINGS
BY HOT WATER

AND UPON

HEAT AND HEATING APPLIANCES IN GENERAL

WITH

AN ENQUIRY RESPECTING VENTILATION, THE CAUSE AND

ACTION OF DRAUGHTS IN CHIMNEYS OR FLUES,

AND THE LAWS RELATING TO COMBUSTION

CHAS. HOOD, F.R.S., F.R.A.S., &c.

RE-WRITTEN By

FREDERICK DYE

AUTHOR OF 'HOT WATER SUPPLY,' ETC. ETC.

SECOND NEW EDITION

HonUon:

E. & F. N. SPON, 125 STRAND
fltfo Sorfc:

SPON & CHAMBERLAIN, 12 CORTLANDT STREET

1894

Engineering
Library

PREFACE.

IN undertaking the recompilation of the late Mr. Hood's
deservedly popular and valued book, it is with a feeling that
the task might probably be an unsuccessful one, except for
the fact that different methods and principles, due to the
ever-varying requirements, are being continually brought to
the front, and very many modifications in details and appliances
have been introduced since the last edition of the book in
question was published.

Natural laws, of course, do not vary, and consequently
many of the results obtained by Mr. Hood, evidently at great
pains and research, will be repeated with but slight variation,
a variation only brought about by the better and more precise
appliances we now have at command ; but it is peculiar to note
that, in studying the results brought about by any natural law,
we have, to a very considerable extent, to consider many other
branches of natural phenomena, and with a view to make
everything as comprehensive and easily understood as possible,
a brief notice upon heat, in its application to hot-water work,
has been introduced, preceding the chief subject-matter under
discussion. It is hardly reasonable to suppose that every one
who takes up this book can be fully acquainted with all the
properties of applied heat, yet it will be obvious that this
knowledge, if only in a limited or elementary form, is practi-
cally of necessity, if the perusal of this work is seriously
undertaken.

Successful hot-water engineering, whether for heating
purposes or for domestic supply (now considered to be two
distinct branches), is of all things perhaps the most dependent
upon a very tolerable knowledge of nature's rules, a know*

vi Preface.

ledge, unfortunately, not possessed by the great majority of
even our best class workmen, and on this account errors are
of the most frequent occurrence, particularly when circum-
stances make it necessary to carry out an undertaking some-
what contrary to the customary method. Of course, pro-
blems arise very commonly which need an advanced degree
of skill to solve them, but this is the exception rather than
the rule. If men who have intelligent ideas, and hope at
some future time to control other workmen, were to devote
a little time to reading up elementary works upon such sub-
jects as natural philosophy (matter, motion, and heat), hydro-
statics, &c., a pleasing study would be opened to them, and
the knowledge would be of evinced value almost daily. In
fact, any one interested or engaged in any profession or
pursuit embracing any description of mechanics, would derive
a most marked and obvious benefit by a knowledge of natural
laws, without which knowledge very many undertakings must
resolve themselves into mere guess work or crude inventions.

If the whole credit of bringing the science of heating,
particularly by hot water, to the forward state it now is in,
is not due to Mr. Hood's labour and researches, there is no
one who will begrudge him the greater share of it, for we have
to remember that his first treatise was published in 1837, and
although many of the rules laid down by him are now com-
mon knowledge, the information he gave to the world at that
early date was of an exceedingly advanced character, and
much beyond what was commonly known at the time. In
his death, the scientific, and also the social world, suffered
a genuine loss.

F. DYE.

CONTENTS.

CHAPTER I.
HEAT.

Material and kinetic theory Experiments and results Transmission
of heat. CONDUCTION Conductive properties of materials Utility
of poor conductors Diffusivity. RADIATION Radiating power of
substances and surfaces Radiant heat and the atmosphere Action
of radiant heat. CONVECTION Water and its composition and
properties Action of convection Experimental results Convection
of air and gases Advantages of hot water as a heating medium

Page I

CHAPTER II.
CIRCULATION OF WATER, &c.

UPON THE CIRCULATION OF WATER Theory and phenomena Tred-
gold's explanation and Hood's criticism and theory Actual cause of
circulation Variation in results- Motive power Table for deter-
mining motive power. CONNECTING PIPES TO BOILERS Direction
of pipes Multiple flow and return services Disadvantages of hori-
zontal pipes Various simple forms of apparatus and their leading
features demonstrated The most practical method . . . . 28

CHAPTER III.
AIR IN PIPES SUPPLY OF WATER EXPANSION OF PIPES.

AIR IN PIPES Accumulation and dislodgment Air pipes and cocks-
Stoppage of air vents. WATER SUPPLY Provision to replenish loss
by evaporation, also when water is drawn off Expansion of water by
heat Capacity of supply cisterns Overflow Position of cistern
Service pipe and connections Rain or hard water Sediment or lime
deposit Useful appliance for small purposes Flushing and cleansing.
EXPANSION OF PIPES Provision for expansion Measure of expan-
sionPipe bearings . . . . . . . . . . . . . . 47

viii Contents.

CHAPTER IV.
IRREGULAR FORMS OF APPARATUS.

Dipping pipes below doorways and other obstacles Its effect upon the
motive power and general efficiency Velocity and its effect Practical
T/. theoretical results Retrograde motion Calculations as to *' dip-
ping " pipes Other phenomena Theory as to results obtained im-
mediately the heat is first applied to the boiler . . . . Page 60

CHAPTER V.

IRREGULAR FORMS OF APPARATUS continued.

Other and more irregular forms of apparatus Methods of calculating
the resistance experienced A phenomenon opposed to a theoretical
basis Method of assisting the circulation in an irregular form of
apparatus Hood's suggestion to this end and its advantages and
disadvantages Another and practical method of effecting a good
circulation below the boiler level The tank system Further informa-
tion as to expelling air . . . . . . . . . . . . . . 74

CHAPTER VI.

CAUSES AFFECTING CIRCULATION OF WATER IN APPARATUS.

Friction Table of relative degrees of friction in different sized pipes
Different purposes for different sized pipes Limit to circulation As to
limiting the length of services Obstructions and faults Erratic results
and their causes The effect of air in circulating pipes Reversed cir-
culations As to whether the flow or the return services should contain
the greatest amount of water . . . . . . 87

CHAPTER VII.
EXAMPLES OF HOT-WATER APPARATUS.

Describing some examples of the average apparatus A small apparatus
for a lean-to greenhouse Description of boiler Arrangement of pipes
Water supply, &c. Another apparatus suited for a small conserva-
tory General description, position of boiler, &c., &c. Description of
another conservatory apparatus A larger apparatus to heat two glass-
houses Pipes in channels General description A large apparatus
to heat a range of five glass-houses with melon pits Main pipes and
their uses Carrying mains in trenches Branch services Pits with
bottom heat Evaporating troughs Capacity of air for moisture
Necessity of providing moisture Position of pipes as regards roots,
shrubs, &c. . . . . . . . . . . . . . . . . 96

Contents. ix

CHAPTER VIII.
BOILERS.

Heating surface, direct and indirect Horizontal and vertical Different
resulting effects due to different conditions of the fuel Hood's
standard of heating surface areas, and its application Boiler-makers'
lists, and the deduction necessary to be made from them Flue surface
and its value Action of flames and heated gases in flues
Fletcher's heat collectors Suggested new standard value of different
heating surfaces Small and large waterways Deposit, its effect and
removal Cast and wrought boilers Area of furnace bars
Hood's table, and necessary additions thereto Independent boilers
and fixing Gas boilers Coke boilers, the " Star," " Coil," " Finsbury,"
" Horse-shoe," " Ivanhoe," " Dome-top," " Independent terminal end
Saddle," " Challenge," and " Viaduct " Page 133

CHAPTER IX.
BOILERS FOR BRICK SETTING.

Saddle boiler and modes of setting it fully described Water bars and
connecting Check ends and waterway fronts Cross tubes Flued
saddle boiler The " Colonial " boiler The " Climax " boiler The
" Imperial " boiler The " Delta " boiler The " Excelsior " boiler
Wagstaff 's tubular boiler The " Champion " boiler Week's tubular
boiler Water bars for coil and tubular boilers The " Python " boiler
The Trentham Cornish boiler 182

CHAPTER X.
APPLIANCES AND FITTINGS FOR HORTICULTURAL WORKS.

Hot-water pipes and fittings Price list Jointing pipes The rust joint
Red and white lead joint Rubber ring joint Improved expansion
and other joints Stop valves and their uses The throttle valve
The slide valve The medium screw valve The reliance valve
Furnace fittings . . . . . . . . . . . . . . 217

CHAPTER XL
QUANTITIES FOR HORTICULTURAL WORKS.

Hood's rule and its application Hood's calculating table and notes
thereon Rapid calculating table and notes thereon . . . . 238

x Contents.

CHAPTER XII.
FUEL, STOKING, AND ATTENTION TO HORTICULTURAL WORKS.

Fuel Steam coal, coke, &c., and its use Sulphur Stoking and regula-
tion of the fire Damping down Attention to air-vents Flue cleaning
Frost, and precautions necessary Non-freezing solution Clean sur-
faces to ensure full radiation of heat . . . . . . Page 247

CHAPTER XIII.
UPON WARMING BUILDINGS (Low PRESSURE).

Distinction between horticultural and building works Pressure and how
exerted Calculations for pressure Shapes for boilers when pressure
excessive Pressure does not aid circulation Comparison in size of
pipes Air cocks and vents Expansion pipe Water supply . . 254

CHAPTER XIV.
PIPES AND APPLIANCES FOR BUILDING WORKS.

Pipes and fittings Qualities Price list Joints Gilled radiating pipe
Coils and radiators, and their distinctive features Box coil Coil with
expansive joint Coil cases and objections thereto Connections
Cannon's radiator The " Universal " radiator Rosser and Russel's
radiator Sanderson's radiator Heap's radiator Saturation of the
air Ventilating radiators Stop valves . . . . . . . . 262

CHAPTER XV.

QUANTITIES.

Hood's rule and suggestions, and their application Calculations of
cubical capacity Varied circumstances to be considered Table for
rapid calculations . . . . . . . . . . . . . . 277

CHAPTER XVI.
EXAMPLES OF LOW-PRESSURE APPARATUS FOR BUILDINGS .. 280

CHAPTER XVII.
HIGH PRESSURE APPARATUS.

Phenomena of Ebullition Heating of water in sealed vessels The high
pressure system Size of pipe Boiler coil Motive power Expansion
pipe and its use Filling Joints Stop-cocks Testing Advantages

Contents. xi

and precautions Frost Non-freezing fluid Uses of this system
Proportions Temperature and pressure table Modification of H.P.
apparatus Regulating valve The application of the Building Act
Example apparatus . . . . . . . . . . . . Page 301

CHAPTER XVIII
WARMING BUILDINGS BY HEATED AIR.. .. .. .. 313

CHAPTER XIX.

HOT-WATER WORKS FOR BATHS, LAVATORIES, AND OTHER
DOMESTIC AND GENERAL PURPOSES.

Circulation Boilers and incrustation Pipes, taps, and other fittings and
appliances Covering pipes and reservoirs for the conservation of heat
Conversion of a tank apparatus to the cylinder system Twin boilers
and services Improved and other systems ; peculiarities noticed from
experiments, and their results in practice Coils and coil services
Faults and sources of trouble Accidents and sources of danger
Safety valves, &c. Low-pressure boilers, also fitting high-pressure
boilers for temporary low-pressure work . . . . . . . . 329

CHAPTER XX.

COMBUSTION ; ITS APPLICATION TO WARMING PURPOSES BY
GRATES, &c.

Stoves and grates Value of radiant heat Smoke Slow combustion,
advantages and disadvantages Utility of the " Blower " to grates
Dr. Arnott's principle, and its unique value Fire-brick and poor heat
conducting materials Grate backs and other improvements Process
of combustion Carbonic acid and oxide Bituminous fuels Products
of perfect and imperfect combustion Carbon and hydro-carbon
Soot . . . . . . . . . . . . . . . . . . 439

CHAPTER XXI.
CHIMNEYS.

Draught in chimneys, cause and effect Causes of sluggish draught
Stoves v. grates Sizes and areas of chimneys Suggested sizes for
horticultural works Residence chimneys A common but little known
cause of trouble Pipe chimneys Descending chimneys "Pilot"
stoves . . 4 . .... . . 452

xii Contents.

CHAPTER XXII.
VENTILATION.

Ventilation by natural or mechanical means Quantity of air per person
Table of quantities for various requirements Ventilation to living
rooms Extract flues Table of velocities at different temperatures
Air propulsion Relation of inlets to outlets Points of entrance for
cold or heated air . . . . . . . . . . . . Page 465

CHAPTER XXIII.

THE METROPOLITAN BUILDINGS ACT. ITS APPLICATION TO HOT-
WATER, STEAM, AND HOT-AIR WORKS, AND TO CHIMNEYS AND
SMOKE-FLUES .. .. .. .. .. .. .-477

APPENDIX .. .... 488

INDEX .. .. 503

PRACTICAL TREATISE

UPON

WARMING BUILDINGS

HOT WATER.

CHAPTER I.

HEAT.

Material and kinetic theory Experiments and results Transmission of
heat. CONDUCTION Conductive properties of materials Utility of
poor conductors Diffusivity. RADIATION" Radiating power of
substances and surfaces Radiant heat and the atmosphere Action
of radiant heat. CONVECTION Water and its composition and
properties Action of convection Experimental results Convection
of air and gases Advantages of hot water as a heating medium.

THE sensation produced when we approach or touch
anything of a high temperature was, until a comparatively
short time ago, attributed to the presence of an infinitely
subtile material, matter or fluid (whatever one likes to desig-
nate it) that pervaded substances that had been acted upon
in a manner to make them what we call " hot " ; this delicate
fluid being imponderable and, in fact, impalpable to all our
senses except that of feeling. When the material assumed a
redness from heat, it was not supposed that the fluid itself
was thus made visible, but that it was merely an altered
appearance of the substance due to the presence and con-
dition of the fluid. The name given this material was Caloric
(calor^ heat) of the Material Theory.

Side by side with this belief was another which for some

2 Warming Buildings by Hot Water.

time did not receive so much favour, by some inexplicable
cause, but which now is considered to be, and is recognised
by all without exception, as the true cause of the phenomena
under discussion.

By this latter theory we understand that heat is wholly
and solely motion nothing more and nothing less a rapid
movement of the small particles (molecules) of which all
descriptions of matter are made up ; the rapidity at which
the particles move being the index to the temperature, so to
speak ; that is, the more rapid the movement the greater the
heat felt, and vice versd. This has received the title of
the Kinetic (motion) Theory.

Great were the contests at the time that these two theories
were approaching an equal footing, the followers of one having
as many irrefutable arguments as the other ; but Count
Rumford, Sir Humphry Davy, and more recently Professor
Tyndall, are chiefly responsible for the victory of the kinetic
principle.

The first of these scientists received his chief impressions
from noticing that in boring cannon the gun itself became
heated, the shavings noticeably more so, and also the tool ;
and this heat was evolved and felt for however long a period
the boring was continued. Sir Humphry Davy's chief or
best known experiment was to cause a blunt steel tool to
revolve at a high speed against the bottom of a metal cylinder,
this cylinder being surrounded by another and the space
between rilled with water, and so long as the tool revolved
the friction produced sensible heat, and the water attained a
high temperature whether for an hour or days. It requires
but little discernment now to see how opposed this is to the
material theory, in which substances or bodies were supposed
to have a capacity for so much hidden heat (that is, to hold or
have room for a certain quantity of heat which did not manifest
itself except under certain conditions), for these experiments
showed that two very small pieces of metal, if kept in friction
one against the other, were capable of giving out heat for an
almost endless period, or until they were worn away. Then

Conduction of Heat. 3

again, with our most precise and delicate appliances, it has
been impossible to discover the slightest increase in heaviness
in a body after it has been heated, yet the lightest gases and
elements known to us have a very sensible weight.

Heat transmits or manifests itself to our sense of feeling
in three ways, viz. by

1. Conduction.

2. Radiation.

3. Convection.

All these three methods intimately concern the art of heating
by hot water, and a knowledge of them is accountable for the
majority of the improved appliances introduced.

i. CONDUCTION OF HEAT.

This is the mode by which heat is transferred through or
about a material or body ; but its effect is chiefly noticed with
solids, some of which possess great powers of conductivity
although fluids (both liquids and gases) possess this property
in a limited form.

In discussing hot-water work it is not with the conductive
powers of fluids that we have to deal, for, as just mentioned,
the property is manifested to such a trifling extent as to be
useless for practical purposes, excepting when it is desired to
prevent loss or transference of heat, as fluids come under the
heading of poor conductors of heat, of which we shall show
the utility presently.

Water is a good absorber of heat, and as a generally
applicable rule we may consider that anything that imbibes
heat readily is just as willing to give it up again ; conse-
quently, in water we have an exceedingly cheap and available
material in the greatest abundance, admirably suited for the
absorption and dispersion of heat needed in hot-water work.
But these two qualities which it possesses are by no means all
that is necessary for a successful apparatus ; for we cannot
have the heat direct from the water itself, owing to the

B 2

4 Warming Buildings by Hot Water.

necessity of inclosing it in some form of vessel or container
(piping) ; and if the material of this container is not a good
conductor of heat, all the good qualities of the water and
other parts of the apparatus are rendered nil. And further
than this, the materials must not only possess successful
conductive powers, but must also have another quality which
will be found under the heading of Radiation.

If we were to use papier-mache pipes (as are used largely
in America for cold water) we should get the very worst
results, the same with any other material (such as earthen-
ware) having a low conductive power ; but were we to use
pipes of silver (having the outer surface adapted for radiation)
an improvement upon iron would be effected, as the table
which follows will show :

COMPARATIVE CONDUCTIVE POWERS OF SUBSTANCES.
(Wiedemann and Franz.)

Conductivity.

Silver 100*0

Copper 73-6

Brass 23*6

Iron 11*9

Lead 8-5

German silver 6-0

(M. Despretz.)

Silver 97'3O

Copper 89-82

Brass 75*20

Cast iron.. 56*90

Wrought iron , 37'43

Lead 17*96

Marble 2*36

Firebrick 1*14

Water 0*90

An appreciable difference exists between these two tables,
as will be seen at a glance, although the different substances
follow in rotation alike in both cases ; but it is worth noting
that Mr. H. G. Madan, in his excellent work upon heat (1889)

Conduction of Heat. 5

follows the former table closely, his figures standing as follows,
silver being taken as the standard = 100.

(Madan.)

Conductivity.

Silver 100*00

Copper 74/00

Iron 12*00

Lead 8*50

Marble 0*15

Glass 0-05

Wood o-oi

Hood quotes the second (Despretz's) table. When
a material is subjected to heat it is supposed that the
particles or molecules (of which the substance is built up)
nearest the source of heat are set in motion, this movement
being of a revolving character similar to what we have on a
vast scale in our planetary system, bodies rotating and
travelling around and about one another (but at present this
is mere hypothesis, as the motion has never been detected by
the most careful microscopic treatment). As the temperature
increases the rate of motion is increased in like ratio ; but the
mere increase and decrease of motion and proportionate
increase and decrease of temperature do not accelerate or
retard conduction in any important way, as the latter effect
is due to a property possessed in a greater or less degree by
the material itself, which either permits of a free motion of its
particles which allows of a ready transference of the motion of
heat, or the reverse.

For the present purpose we may consider that the
property of conduction only applies to the metal composing
the boiler plates and that of which the pipes or heat-diffusing
appliances are made ; conduction cannot be said to apply to
the fire around the boiler or the water within it, nor the air
outside the pipes or the water within them, it only applies to
the material that separates the fire from the water, or the
water from the air, respectively. If we could apply the fire
heat directly to the water and transfer the heat from the
heated water without the intervention of. any material, how-

6 Warming Buildings by Hot Water.

ever good its conductive power may be, we should get much
better results : that is to say, by a less consumption of fuel
and in considerably less time.

There is not the least doubt that heating by hot water
would never have attained its present popularity if the
materials so well suited for the purpose were not so cheap and
easily obtained, for in cast iron we have a substance possess-
ing ample strength, easy of adaptation as to form, size, &c.,
by the common process of casting, cheapness due to abund-
ance, and what is more necessary, a good conductive power.
Cast iron is of greater conductivity than wrought iron by a
considerable degree, and what is objectionable in wrought
pipes (even if of as little cost) is that its greatest conductive
power lies with the grain or fibre and not across it, in the way
it would be of the greatest use for this purpose.

It is difficult to say which of the three modes of conveying
heat is of the greatest importance in hot-water work, for each
is most intimately concerned in the success or non-success of
the work. If the boiler or pipes were constructed of any sub-
stance possessing a low conductive power there would be an
almost impassable barrier introduced at once, the heat being
closely imprisoned within the apparatus, although ready in
every sense of the word to dissipate itself, if the circumstances
were favourable.

Poor conductors of heat enter into the construction of
nearly every apparatus that is erected, in some form or
another, as it is not sufficient that we merely transfer some
portion of the heat of combustion to the water and subse-
quently to the place to be heated : we have to most severely
consider the question of economy in fuel and labour and con-
sequent wear and tear, and a hot-water engineer's good repu-
tation is frequently based upon his success in this particular ;
indeed, it is no uncommon thing for an apparatus to be
either partially or totally unsuccessful, owing to its dissipating
heat where the heat has no valuable use.

First may be mentioned the great use made of firebricks
in the construction of the flues surrounding the boiler (if the

Conduction of Heat. 7

boiler is not an independent one), this material having the
double advantage of poor conductivity and a refractory
nature, so that although a flue surrounding a boiler is of
course bounded on two sides, one by the boiler and one by
firebrick, it is only on the boiler side that absorption of heat
takes place to any material extent ; and the peculiar nature
of the clay of which firebricks are made makes it well suited
for the purpose owing to its good wearing properties under
the influence of heat.

Another instance of the utility of a poor conducting
material is when some portions of the service pipes have to be
carried along in cold situations (occasionally out of doors)
where the radiation of heat is often worse than useless
owing to the decrease of heat it necessarily occasions in those
situations where the heat is required. In such instances the
pipes have to be covered with some material or compound
having a low conductive power so as to conserve the heat, i.e.
retain the heat within the pipes, which will be spoken of more
fully presently.

Another important instance of the kind is when the boiler
is of the independent description requiring no brick setting,
these boilers being most liable to loss of heat in a way that is
opposed to good results. It will be noticed that with all
independent boilers, including those illustrated in this treatise,
the whole outer surface, both of the portion that contains
water and of parts constituting the fire-box, is fully exposed
to the air and all its influences. In an actual experiment
made with a vertical dome-topped boiler, it was found that
a coil situated a short distance away took one-third longer
time to heat when the boiler was exposed, than when it was
covered with a poor conducting compound. It will be readily
understood how quickly the heat is transferred from the fire
to the outer surface of the boiler, and the next chapters upon
radiation and convection will show clearly how soon the heat
is disposed of when once it has reached this point.

For some very obscure reason the word " non-conductor "
has become quite common, through heedlessness probably, as

8 Warming Buildings by Hot Water.

there is no such thing as a non-conductor of heat, although very
many substances rank as exceedingly poor conductors, and on
this account answer general purposes almost as well as a
non-conductor would. Professor Tyndall once informed the
writer that asbestos, which answers excellently as a poor
conductor with ordinary heats, quite failed, in some ex-
periments he made with very high temperatures even though
an air space existed between the asbestos and the source of
heat.

There is another feature in the conductive power of iron
to be considered, as its application is becoming more and
more general, and with very satisfactory results. This has
been very correctly named " diffusivity," meaning the power
that iron has in diffusing heat over a large area (of iron) ;
simply another name for conduction, but the result bears a
different application. If we take a hot-water pipe and charge
it with water at a temperature of, say
Fig. i. 1 80, the heat at the outer surface will

bear a close relation to these figures ;
but if we add a number of gills or
feathers to the pipe, as at Fig. I, the
heat will instantly diffuse itself into
these plates, and the result will be that in-
stead of a small area at a high tempera-
ture, we shall get a greater area at a lower temperature, that
is to say, we shall get a greater radiating surface but giving off
cooler rays of heat, and a greater surface for air contact, but
the air will not be heated so greatly. We do not expect to
get a higher aggregate temperature, as in both cases the
results are only brought about by a certain quantity of
water at 180, but by this means we are able to diffuse the
heat about an apartment in a rather more equable manner.
But the chief advantages are, that the lower temperature
of the radiating surface prevents accidents, &c., when a
person's hand or body comes in contact with it, and with a
lower temperature we are less likely to get odours arising from
the decomposition of any matters that may fall upon the pipes

Radiation of Heat. 9

in the form of dust, &c. These things, and also the saturation
of the air which is affected, are worth consideration in hot-
water work, but in stove work they are of the greatest
importance, as will be explained when treating these articles.

When treating open fire-grates we shall speak of the
disadvantages experienced by the good conductive power of
iron, and the various means of obviating the difficulty.

RADIATION OF HEAT.

To clearly grasp the existing theory of radiant heat (radio,
to emit beams or rays) we have to understand that there
exists around us, in every conceivable space, an infinitely
thin and subtile medium, which is called the ether (or the
interstellar medium), which is quite independent of the atmo-
spheric air, or, we may say, is mixed with it, and this medium
is the means by which radiated heat, as also light, is trans-
ferred or conveyed from a hot body to surrounding objects.
Radiant heat is therefore the motion of heat transmitted to
the ether, which motion is carried or propagated in the form of
waves in straight lines from the source of heat.

It is not at all necessary that air be present to effect the
phenomena of radiation, as if we suspend a thermometer in a
vacuum, and apply heat outside, or place a heated substance
in the vacuum and the thermometer outside, or place both in
a vacuum, we find that the transmission of radiant heat is still
manifested ; consequently we must believe that this ethereal
medium is of a totally different character to air or gases, as
it cannot, apparently, be withdrawn from a vessel in the
manner we should exhaust it of air.

We have already mentioned that the fact of a material
conducting heat satisfactorily, as iron does, is not sufficient to
ensure success to a hot-water apparatus, for the simple reason
that the heat brought to the surface of the pipes only, is
practically useless, as to benefit by its presence we must have
it striking against us and surrounding objects in the form of
radiant heat, and it must also part with its heat to the sur-

io Warming Buildings by Hot Water.

rounding air. Silver pipes, as mentioned, would give the best
possible results so far as conduction is concerned, but a highly
polished silver surface stands the very lowest in a scale of
radiating power, consequently this costly material would not,
with its excellent conductive power, answer so well as plain
black cast iron, as the following table will show :

RADIATING AND ABSORBING POWERS OF SUBSTANCES.
(M. Pouillet.)

(The absorbing and radiating powers of materials are equal, but their
reflecting powers are in exact inverse ratio.)

Radiating and
Absorbing Power.

Lampblack 100

White lead 100

Glass 90

Cast iron, polished 25

Wrought iron 23

Zinc, polished 19

Steel 17

Brass, roughly polished II

Brass, highly 7

Copper, either cast or deposited on iron . . 7
Silver, highly polished, either cast or \

hammered / '

(Leslie.)

Lampblack 100

Water (by estimate) 100

Glass 90

Plumbago 75

Tarnished lead 45

Clean lead 19

Silver and copper 12

Neither of these tables gives a comparative figure for plain
cast iron (unpolished), but from results obtained in practice
this should stand at about 60, if the outer surface is untouched,
i. e. having its own natural coating of oxide.

From these tables it will be conspicuously noticed that
polished metals are the very worst radiators, and on this
account it is that kettles, urns, and the copper cylinders
sometimes used in hot-water supply apparatus are, or should

Radiation of Heat. n

be, kept polished, to prevent loss of heat by radiation, the
polished surface so very successfully preventing radiation.
The writer's best remembered experience of this was the
fitting up of an electroplated radiating coil in the hall of a
gentleman's residence, and this was a most obvious failure,
although no blame could be attached to the boiler, and the
coil felt hot if touched, and succeeded in warming the air
somewhat.

The radiating power of a body is not due to its material
substance, but to the nature of the oiiter film or skin ; so that
if we coat a bad radiating but good conducting material
with say lampblack, we shall get the best possible results.
For example, silver has the highest conducting power, but
the lowest degree of radiation ; but coat a silver pipe with
lampblack, and we have the highest conceivable success, and
the rougher the coating of black the greater the radiation,
as a rough material presents a greater surface than a smooth
one, and radiant heat (the dark rays) seems to leave a rough
surface (which really consists of a great number of minute
points) more freely that a smooth one.

Lampblack is supposed to have no reflective power
whatever, and consequently it is classed as a perfect radiator
at least as perfect as any known at present. This has led to
a belief that colour materially affects radiation of heat, which
is correct so far as regards rays of heat that proceed from a
luminous body, these standing in order from white to black,
the lightest radiating the least, and vice versa. But this has no
interest to the subject being treated, as we have only to deal
with radiation from non-luminous bodies, and colour makes no
difference whatever to the free radiation of dark rays of heat.
This brings us to consider what is the best material to
coat the coils and pipes of a hot-water apparatus with. It
must be noted that the table of radiating powers given only
applies to dark rays, that is, rays of heat proceeding from
substances below about 500.

Lampblack is doubtless the best of all materials to coat
coils and pipes with, but this has an objection in the fact that

1 2 Warming Buildings by Hot Water.

it does not increase the sightly appearance of an object, and
consequently recourse is had to paint, which fortunately
possesses radiating powers as nearly as possible equal to
lampblack ; and for rays of heat proceeding from non-lumi-
nous bodies, white paint will give about as good results as
black, or any intermediate colour. Consequently, if we use the
improved form of radiating coils (of which we shall speak fully
presently) in a living-room, we are enabled to colour them to
suit the surrounding decorations without any prejudicial effect
upon their radiating efficiency. Two which the writer had
erected in a drawing-room, and coloured cream and gold,
with marble tops, were eminently successful, both for
efficiency and good appearance.

These ornamental coils are frequently bronzed for the
sake of good appearance, and they act very fairly ; but for
radiating power preference should certainly be given to paint,
as the bronze, whether copper or an alloy like brass, is com-
posed of poor radiating materials, as well as being of a
polished metallic nature.

A thick film of oil stands at "59 in the scale of radiating
substances with lampblack at 100, and as the majority of
metallic oxides (which go with oil to make paint) are good
radiators, a coating of such a mixture is very satisfactory.

There is a material which is an excellent radiator, but
which, although not used in connection with hot-water work,
is used to a fair extent upon stoves, and that is glass, which
forms the glazed surface of tiles of nearly every description.
Glass, it will be seen, stands at "90 in the scale of radiat-
ing powers, but a great objection possessed by it, as also
by the substance of all tiles, is their low conductive powers ;
consequently, although the outer film of glass readily
sends out its heat, the difficulty is to transfer the heat to the
outer surface, and on this account a glazed earthenware pipe
would be most objectionable as a radiating pipe, although
the glazed surface itself cannot be found fault with. The
question of the low conductive power of earthenware and fire-
brick substances will be spoken favourably of presently, as it

Radiation of Heat. 1 3

is a material largely used where escape of heat is to be
prevented, and this is why an earthenware bath (unglazed
inside) is so delightful to use.

We have at present only spoken of radiant energy as
existing at the extreme outer surface of the radiating media ;
we now have to consider how the agreeable effect of the
heat is experienced by the body. First, it is to be understood
that radiant heat does not (so far as this subject is concerned)
increase the temperature of the atmospheric air. It is most
commonly thought that the heat radiated from a bright fire is
warming the air, but this supposition can be disposed of by
placing two thermometers a few feet from the front of the
fire, one facing and one with its back to the source of heat,
and notice the difference of temperature, although the same
air surrounds both. But there is a more convincing and irre-
futable proof of this in the fact that although on a summer's
day the air might be warm near the earth, if we left the earth
in a balloon for instance we should find the air get colder
and colder as the distance increased, until at a high elevation
(above the clouds) a thermometer would probably register a
freezing temperature ; and yet all this time we should begetting
nearer and nearer to the sun, which might be shining brightly all
the while. Radiant energy is felt in the form of heat on all
bodies, our own bodies included, and air is heated by
coming in contact with objects that have been heated ; but in
the case of the earth, we who are upon its surface have the
benefit of the sun's heat agreeably transmitted to us owing to
the presence of water vapour in the atmosphere, which fulfils
two exceedingly beneficial purposes without which existence
would be next to, if not quite impossible.

Now, water vapour is a very great absorber of heat, and in
this instance it firstly tempers the fierce heat of the sun that
is radiated upon us, and secondly it effectually prevents the
instantaneous loss of heat by re-radiation from the earth's
surface and the objects upon it, which would take place if it
were absent. If our atmosphere were what we may call pure,
that is, free from the admixture of foreign substances, water

14 Warming Buildings by Hot Water.

vapour in particular, the presence of the sun would cause a
really scorching heat to be felt, and its absence would be
instantly noticeable by the loss of heat and a most intensely
bitter cold. As we get away from the earth's surface the
atmosphere becomes less humid, and the sun's heat is felt
and lost almost at the same instant, the air remaining
excessively cold and robbing us of heat by convection (as
will be understood directly) at a great rate.

The peculiarity possessed by the atmosphere in not
absorbing radiant heat (by which it would be made intolerably
hot) is of particular benefit to mankind, whose nature is
specially adapted to profit by it. Indeed it must be notice-
able to every one that we require and are rendered comfort-
able by a much higher temperature for our bodies than for
the air we breathe, which is evinced by the pleasure most
people feel in breathing the sharp air of a fine winter's day,
provided the body is well clothed and so kept at a good
heat.

This naturally leads us to consider which form or method
of heating is best suited to fulfil these natural and conse-
quently most desirable conditions. Although each system
will be treated fully hereafter, it may be mentioned that the
methods are practically confined to four only, viz. open fires
(radiant heat and air heated by contact with warmed objects) ;
hot-water and steam pipes (radiant heat and air heated by
contact with the pipes and by warmed objects) ; stoves (same
as hot-water pipes, but with different and less pleasant
results) ; hot air (air heated by contact with hot bodies and
conveyed where required by pipes or conduits, and some
radiant heat from bodies warmed by the air).

Radiant energy is projected from the source of heat in the
direction of a straight line, but its motion has been likened to
a series of waves which continue in one direction irrespective
of other influences, as Mr. Madan says, " like the waves on
water pursuing their course uninterrupted by tides and other
influences." This motion or it had better be called heat-
loses its intensity very quickly as it leaves its source ; not that

Radiation of Heat. 15

we may consider the heat itself to be lost, but it quickly
diffuses itself over a wide area. Thus we get it over a larger
space but at a lower temperature, and there is no objection
to this, for we are enabled to heat a large space from one
source of heat. As already mentioned, these rays pass
through the atmosphere without affecting it, and their effect
is only experienced on surrounding objects. Thus, in a room,
the walls, furniture, and other objects receive the heat which
impinges, so to speak, upon them, and they in their turn
re-radiate the heat in various directions to various extents
depending upon their radiating power and other properties,
so that when we stand in a part of the room where the rays
from the fire do not directly strike us we feel an equable heat
(provided we are not near any rapid conductor of heat or near
a window where a cold down-current nearly always exists, as
will be explained later), owing to the dark rays of heat from the
surroundings being projected in all directions. But immediately
we get near the fire and obstruct some of the rays that come
directly from it, we feel hotter on the side nearest the source
of heat than we do on the side removed from it, owing to the
greater intensity of that which we receive from the fire than
that which we receive from the warmed objects the other side.
A very good illustration that heat travels in straight lines, is
to hold any object in front of us as we face the fire and
notice how instantly the heat is cut off, and a minute observa-
tion made at the moment would show that a greater heat
would be felt from the objects at the back from which we
have not shielded ourselves. If radiant heat did not travel
in straight lines a sunshade or awning would be a very useless
article.

It has been very pertinently pointed out that this fluid
theory of radiant heat, i. e. that radiant energy is transmitted
by a subtile ether, existing in an intermingled state with the
.atmosphere, and beyond the atmosphere (to account for
the sun's rays being transmitted to the earth), may at some
time be exploded like the fluid or material theory of heat
itself (see p. 9). For this is practically the last of the fluid

1 6 Warming Buildings by Hot Water.

theories, and is founded upon mere conjecture, as the fluid
itself has never been detected, neither by weight nor other
experiments ; and what may be considered as rather fatal to
this supposition, is that radiation proceeds about as well in a
vacuum as in the air, showing that although we can exhaust
the receiver of a good air-pump almost perfectly, we do not
apparently abstract this ether, notwithstanding that every
other known fluid can be withdrawn readily,

In hot-water work it is only the dark rays of heat that
have to be considered, as no part of an apparatus, even upon
the high-pressure system, is supposed to exceed about 350
external temperature, and is consequently far from being
luminous. This is so far as concerns the pipes, but in the
furnace of course the dark rays are absent, as all the heat pro-
ceeds from highly luminous fuel. The surface of a boiler
nearest the fire gathers heat in several distinct ways, viz. by
radiation from the glowing mass, by contact with the glowing
mass, which we might call absorption, and by contact of heated
gases. Of course the greatest effect is brought about by
radiation from, and contact with, the glowing fuel, which gives
the water every opportunity to manifest its rapid power of
absorption. Flame needs no consideration, as coke is the fuel
invariably used (except at some special time, or under some
special circumstances), but the hot gases evolved, which it is
understood include the highly heated products of combustion
(carbonic dioxide, carbonic oxide, &c.) are an element of some
importance, as the flues which are carried round and about a
boiler have no incandescent fuel within them, and the surfaces
within these flues receive heat from the hot gaseous products
only.

Heated gases, it will be found, only do effective work in
the boiler flues by coming into actual contact with the surfaces,
which surfaces, if of an absorptive nature, take up some of their
heat, and if by any means the heated products are able to es-
cape without touching the surfaces in question, decidedly less
good results will be obtained. It is peculiar to note that these
gases manifest to a great extent a property which is very

Convection of Heat. 1 7

noticeable with flame, and that is to avoid coming into actual
contact with surfaces if there is room and a possible way to
avoid so doing, so that if we surround a boiler with flues larger
than a recognised efficient size, very little heat will be gained
from what passes through them ; yet, on the other hand, we
cannot successfully cramp the flues beyond a reasonable limit,
as will be shown presently.

CONVECTION.

A knowledge of the two subjects, Conduction and Radia-
tion, is of considerable necessity and interest in studying any
mode of heating ; but where we employ water as the medium
for the transmission of heat, the present subject, viz. con-
vection, possesses greater interest than all, and a knowledge
of it is absolutely necessary for the proper planning and
carrying out such work.

Convection (from conveho, to carry up) is described as
" the act of conveying heat by the ascent of heated particles in a
gas or liquid" Water and gases, in fact all fluids, are com-
posed of one or more elements existing in the state of a mass
of exceedingly minute particles, which are termed molecules,
these particles having no cohesive or adhesive properties. In
fact the commonly accepted notion is that there is a distinct
repelling influence existing, which causes the particles, as of
water and particularly of gases, to spread in all directions
when unconfined. For instance, we might compare a mass of
water to a mass of exceedingly fine sand, except for the pro-
perty just explained ; for although the particles of sand are all
free and quite independent of one another, like the particles of
a mass of water, yet we can have a heap of the former, but no
one ever saw a heap of the latter (except in a frozen state). One
reason accounting for the heaping of sand, is that the friction
amongst the particles, owing to their irregular shape, helps
and in fact is the chief cause of their s-upporting one another ;
and although no suggestion has been made as to the shape of
water molecules, we cannot help thinking they must be

1 8 Warming Buildings by Hot Water.

spherical, which would then account greatly for their very
perfect mobility, for if we took, say, a bushel of small coke
(an irregular shaped material) and a bushel of glass balls, and
emptied them on the ground, there is no doubt about the
balls acting very much like a bushel of water would do, viz.
spreading out in all directions, which the coke would not do.

Fluids, however, both liquid and gaseous, possess the
property of mobility in a most marked degree ; the particles
have the most free and independent motion possible to con-
ceive, not manifesting the faintest sign of friction between the
particles, which we are naturally inclined to expect in every-
thing, certainly solids. When water is agitated the particles
glide over and under and around one another without interrup-
tion or resistance in the slightest degree, and on this account,
i. e. the absence of friction, water would want an enormous
amount of agitation to raise its temperature perceptibly to an
ordinary thermometer.

We may therefore consider a body of water when un-
disturbed and of a uniform low temperature, to be a mass of
minute particles, all free to move by the slightest cause ; and
if we take a glass vessel a large tumbler or an ordinary jar
will do we can quickly investigate and become acquainted
with the exact action of Convection. First, it is necessary to
obtain a substance that will be visible in water (for water is
invisible) without giving erratic results, and nothing is better
than amber for this purpose, if ground to a very fine powder,
as the specific gravity of this material is I 080 with water at
I *ooo ; or the finest sawdust of some moderately heavy woods
answers very fairly.* If we apply heat to the bottom of a

* I have tried amber several times, and also mahogany dust ; the
gravity of amber, however, either varies very greatly, or else we have
a far greater number of imitations of this article than we are apt to
suppose, and it is sometimes necessary to discard two or three pieces
owing to their uselessness for this purpose. With mahogany dust there
is very little objection ; it has a tendency to sink to the bottom (the greater
portion of it), but the ascending current of water carries the particles up,
which is exactly suited to the requirements. A substance that wholly floats
.at the top of the water would not answer the purpose at all.

Convection of Heat. 19

vessel charged with water with this dust material in it, we
shall notice almost immediately that some of the particles are
propelled upwards, and as the particles leave the bottom and
lower part of the vessel, other particles will be noticed travel-
ling down from the upper part towards the bottom, to take
the place of those that have ascended.

The exact action is as follows : the particles or molecules
of water in contact with the bottom of the vessel are stationary
before the heat is applied, but immediately heat is transferred
to them they expand in bulk and are thus rendered lighter
(bulk for bulk) than their fellow particles, with the consequence
that they immediately begin to rise like any substance would
that is lighter than its equal bulk of water. We may
consider that these heated and lightened particles of water
(although still of the same composition of water) act like a
foreign lighter material such as cork, and insist upon rising to
the highest possible point, until they have lost their heat and
again become of the same bulk as the other molecules. As
these particles rise they carry up the particles of amber with
them, by which means the action of the water is illustrated.

After but a very short time a steady circulation will be
found to have set in, as at Fig. 2,* and this circulation will
continue so long as heat is applied to the bottom or lower

* It is very interesting to watch this phenomenon, its action is so
regular, and the particles of solid matter (amber or wood) spring up from
the bottom and travel round apparently without any reason or cause, yet
in such a regular and uniform manner ; but it is most interesting to look
at the action from the top, that is through the upper exposed surface of
the water, the particles rising and falling like a stream of animalcula, all
travelling in one recognised direction, and a peculiar result that will be
noticed is, that notwithstanding the disturbance, i. e. the circulation of
the water, the upper surface is undisturbed and perfectly motionless. Never
was there a better illustration of the upper layer of molecules in a vessel
of water forming a skin to the contents. As the water gains in temper-
ature the bottom of the vessel will get encrusted (inside) with minute air-
bubbles showing how the aeration of the water is disposed of, and rendering
water that has been heated so flat and unpalatable. If mahogany dust is
used the water will become impregnated with some of the brown colouring
matter of the wood, but this is not objectionable.

C 2

Warming Buildings by Hot Water.

Fig. 2.

ill"!

part of the vessel. It is doubtful if this circulation would
ever cease while heat is applied, as although we may suppose
that the water would attain a uniform temperature eventually,
this is not the case with a heating apparatus. With this
latter a reduction in temperature takes
place very soon after the water leaves the
boiler, owing to the ready radiation of heat
both by water and iron, as already ex-
plained, and from the contact of cold air,
&c. ; consequently there is always a dif-
ference, more or less great, between the
temperature of the water leaving and that
entering the boiler ; the difference in tem-
perature meaning, of course, difference in
bulk for weight. This is the simple ex-
planation of Convection as applied to
water, but in a later chapter the subject
will have to be dealt with more fully.

There is no doubt that the rapid heat-
ing of water and gases was originally attributed to Conduction
a very reasonable deduction indeed, as it is this phenomenon
that accounts for the transference of heat throughout the mass
of all solids ; but in solids we can obtain a transference of heat
to the portion furthest removed from its source, whether the
heat be applied to the top, bottom, or sides, which is not the case
with fluids, as can be simply tested with the glass vessel just
referred to. If this vessel be rilled with cold water and a
gas flame be applied to the top, it would be found to take a
very great time before the least trace of heat reached the
lower part, showing, as has been conclusively proved, that,
water does not conduct heat at all willingly, and it has been
classed as one of the poorest conductors. If on the other
hand we took a vessel of hot water and placed a very cold
substance at the top of it, a circulation would be noticed at
once, as in this case we simply reverse the action of the
convection currents ; the cooled particles being rendered
heavier (bulk for bulk) than the hot ones, so that they

Convection of Heat.

Fig- 3-

instantly sink to the bottom and hot ones ascend to take
their place, an exactly reverse process to that first described

In an apparatus for heating purposes it will be readily
seen that the vessel just referred to only
illustrates the action of the water in the boiler,
and although we may look upon the pipes from
which the heat is radiated as mere extensions
or continuations of the boiler, the way in
which the hot water is conveyed (or conveys
itself) into them needs a little explanation.

If we construct an apparatus as at Fig. 3,
which consists of a bottle with a cork stopper
(which must fit tightly, and may probably require
waxing over), with two glass tubes passing
through the stopper, one reaching say three-
fourths of the way to the bottom, and the other
not projecting inside in the least degree (for
reasons to be presently explained), and carry
these tubes something like the illustration, we
shall have a model apparatus of simple form,
which will in its action explain everything very
clearly.* When the heat is applied, the circula-
tion will set in almost instantly, and it will set
in at all parts, that is to say, it will not be confined to the
boiler, but will, at the first indication of a movement, be seen
travelling along the pipes in the direction indicated by the
arrows. It is hardly sufficient to say that the motion is brought

* The writer has adopted very humble materials in illustrating this
apparatus, but they possess the advantage of acting with as great certainty
as an elaborately constructed erection, and as the whole model is glass the
result can be noted with greater accuracy than with any metal appliances,
but if any one proposes investigating the matter thoroughly, it would be
worth while having a glass boiler made.

The object in having one pipe at a lower point in the boiler than
the other is to ensure the regular circulation of the water in one direction,
as will be understood ; if the pipes started level with each other a circula-
tion would still set in, but there would be no certainty as to which would
act as a flow pipe and which as the return.

22 Warming Buildings by Hot Water.

about by the fact that heated water is lighter than cold of
the same bulk ; it is really the other way about, as the
phenomenon is wholly due to gravity, that is, the cold water
being heavier that the hot, which, although a trifling distinction,
has a considerable difference for the purposes of this discussion.
The cold water having greater specific gravity than the hot,
has a tendency to sink and find the lowest possible point by
reason of its superior weight, so that when a particle of water
becomes heated and rarefied in the slightest degree, it is in-
stantly pushed away, so to speak, by its surrounding fellows
whose weight is now superior and able to displace the lighter
mass. It can be seen that hot water has no tendency to rise
whatever without being compelled to do so by a superior
force. If a vessel is filled with hot water, no part of it will
raise itself beyond its natural level ; consequently the particles
of warmed water that rise and constitute a convection current,
take up this motion entirely by reason of their being urged in
that direction by a crowd of heavier fellows all jostling and
making their way to the lowest point by their greater weight
or gravity ; and to use the expression attributed to Dr.
Balfour Stewart, " Were there no gravity there could be no
convection ; were it not for gravity it would be of no conse-
quence what part of a vessel we heated, the effect of the
heating would be always the same."

This is a slight digression, but it is to make it more clear
why the circulation or convection current sets up in all parts
of an apparatus at once, instead of locally to the source of heat,
as some might possibly suppose. When the layer of particles
nearest the source of heat are rarefied and pushed up by the
heavier particles surrounding them, this movement is as a
matter of course (owing to the inelasticity of water) trans-
mitted from the highest point, in the same way that there
would be an instant movement from top to bottom of a tube
or vessel of water if we withdrew some of its contents at the
bottom. Consequently, in an apparatus as at Fig. 3, we shall
find that the down and up flow will occur simultaneously from
the highest to the lowest point in the circulating pipes, and

Convection of Heat. 23

the result is the same whether the erection be large or small,
simple or complex, provided its principle is correct.

This is the result with a glass apparatus; with one of
metal a little different conclusion might be arrived at, as
although the heated particles are travelling up one of the pipes
(the " flow " pipe), no heat will be felt externally for a little
while, owing to its being absorbed in many ways by the
pipes, &c., as we naturally cannot expect to have warmth
from the outer surface until everything is warmed within.

No precise table can be laid down to indicate the speed of
convection currents, owing to their being varied by so many
different incidental circumstances, but the speed can be
theoretically calculated by a rule that will be given in the
next chapter. However, it may be considered that no liquid
exists that will give better results than water, owing to its
perfect mobility, and to the fact that not the slightest degree
of coagulation takes place however much it may be used over
and over again, and it is a material that can be obtained
readily and practically without cost wherever the apparatus
happens to be situated.

Many attempts have been made to utilise other liquid
materials with the view of getting a higher temperature, and
so obtain equal results with less pipe, &c., but at present
nothing very satisfactory has been done, owing chiefly, no
doubt, to the fluids which boil at a greater heat than water
being of a more viscid or less mobile nature, such as a satu-
rated solution of common salt or oil, &c. With these and all
fluids of a like nature convection proceeds more slowly, and
the more viscid its nature the slower it moves, until we have
it in a solid or semi-solid state, when the particles will not
circulate at all.

Convection being caused by gravity, it follows that the
more a material (i. e. its particles) expands by heat, the
faster the convection currents must be, and it is on this
account that the circulation of atmospheric air or any such
light gas proceeds with great rapidity. A familiar experience
of this is in gales, which, as well as gentle breezes, are

24 Warming Buildings by Hot Water.

all convection currents ; that is, a flow of cold air conveying
itself to some spot where a rise of heated air is taking place.
Trade winds and ocean currents all proceed in the same way,
except that one is convective currents of air and the other of
water.

Thus far we have considered the question of convection as
applied to the water in the boiler and the pipes, this water
receiving the heat from the fire, which is conveyed through
the boiler plate by conduction to the particles of water that
are in contact with it, these particles starting off immediately,
and conveying the heat to the desired locality ; but before
abandoning this subject we have to see how the heat is
transferred from the pipes or coils to the surroundings, the
heating of which has been the sole object of the apparatus.

It will be readily understood that it is not sufficient to
bring the heated water into the pipes, but this heat must pass
through the substance of the pipe, as it readily does by con-
duction (already explained), and it must freely transmit itself
to the surroundings. Now it has already been shown that by
radiation heat is transferred from a heated surface in direct
lines in all directions, its intensity being governed by the
good or poor radiating powers of the surface coating. With
hot-water pipes, in addition to this, we have another mode
of heat transmission from the surface, viz. by convection,
that is, the heating of air particles in contact with the pipe
and the consequent circulation of air as explained with water,
excepting that with air the action is very much quicker with
equally rapid distribution of the heat.

This takes place quite independently of the heat emitted
by radiation, and it is the argument for and against both open
fires and hot-water pipes by grate-makers and hot-water
engineers respectively. The grate-maker's contention is that
open fires give the only natural result (that is a result exactly
similar to that experienced by the sun), by reason of their
imparting heat to the body and surrounding things, rendering
everything agreeable to the touch and to our feelings and
senses generally, without materially (we may say perceptibly)

Convection of Heat 2 5

increasing the temperature of the air, and certainly without
altering its general character ; whereas with any method of
heating by hot water the cheerful brightness is lost, radiant
heat (the congenial heat) is obtained in a less degree, and we
have warmed air conveyed to our lungs which is not supposed
to impart such a feeling of vitality as a cooler atmosphere ;
and further, that in increasing the temperature the saturation
of the air, i. e. its volume of watery vapour, is not increased
proportionately at the same time as would be the case in
nature, so that a sense of dryness may be supposed to exist.

This is a good list, and a rather strong case for the grate-
maker, and although the hot-water engineer is willing to
contest this argument strongly, it must be contended that his
theories are not quite so forcible and do not appeal so readily
to an average person as the grate-maker's ; but for one par-
ticular purpose the hot-water engineer will be seen to have
much the best of the contest.

The advantages claimed for heating by hot water may be
summed up as follows. By the most ordinary attention an
equable heat can be obtained all the day, and if desired all
night, so that at no time need any part of the house be cold
during early morning, for instance. The heat can be dis-
tributed anywhere and everywhere, so that passages are as
comfortable as the rooms. As just mentioned, the heat does
not fluctuate, as must be the case with grate fires. There is
less need of attention, cleaning, &c. (but it must be mentioned
that an apparatus upon even a moderate scale needs a fairly
experienced person to attend to the stoking). The loss of
the sight of the fire is quickly become used to. As the
heat of the pipes (of the low pressure system) is very rarely
beyond 180, the air is not raised sufficiently in temperature
to make a noticeable difference in its moistness, not even to
those with bronchial affections, who would be the greatest
sufferers. This, however, is open to objection, as the writer has
been told more than once that the difference is noticeable to
these sufferers, and this is partly borne out by the hot-water
engineer sometimes dropping this argument and substituting,

26 Warming Buildings by Hot Water.

" That if a dryness of the atmosphere is noticed, the remedy
is simple, by the introduction of vaporising pans or
troughs." And lastly, for conservatories and horticultural work
it is eminently suited beyond all other methods by its regu-
larity of temperature, the simple method of application, the
ease with which the heat can be regulated as the weather or
outer temperature varies, and the exceedingly simple and
natural means of increasing the humidity of the air or over-
saturating it with moisture, and so rendering it exactly like
what nature provides where the earth is most prolific of ver-
dure. It is most noticeable that wherever both warmth and
a moisture-laden air exist, there abound all nature's best
productions in a degree bordering on extravagance. This is
so different to our English climate with its prevalence of dry
cold winds.

There are other minor points claimed by both sides, but
for general agreeable results in private residences a combina-
tion of the two methods is very satisfactory, provided strict
economy in fuel is not of primary importance.

It will probably have been understood by the action of
convection in water that air instantly makes a move in an
upward direction when it has absorbed heat, partly account-
ing for the great heat experienced near ceilings when a room
is comfortably warm near the floor. The convective action of
air does not proceed wholly from the pipe surfaces, for we
have it from every other object that is warm, whether these
other objects have received their heat by radiation or other-
wise, so that even with open grates we have warmed air to
some extent from its contact with our warm bodies, walls,
furniture, and general surroundings. Air may be said to
receive heat by contact only, and this is what it is continually
doing, robbing everything of heat that it comes in contact
with (unless it be of a less temperature than itself, when it
gets robbed in its turn). This, it may be mentioned, is an
argument used and worn threadbare by some hot-water
engineers as against the open grate, viz. that radiant heat
warms one side of our body whilst the cool air is abstracting

Convection of Heat. 27

heat from the other side, whereas with hot water the air is
directly warmed to a temperature beyond actual coldness.
This argument, although very forcible to a lay mind, is not
strictly correct, as although we get a greater heat one side
than another it is only while we directly intercept the hottest
rays. If we move out of range of these rays we find a fairly
equable heat in all other parts of the apartment.

It simply remains to be said that as heated air takes an
upward direction the instant it is rarefied, all hot-water pipes
and such heating media require to be near the floor, as at the
ceiling it would indeed be a very long time before their good
effects were noticeable below. It is this action that brings
about the up-draught that is found in all chimneys, and it is
an indirect reason why a baker's and pastrycook's oven has to
have a bottom heat to ensure lightness to the articles baked.

28 Warming Buildings by Hot Water.

CHAPTER II.

CIRCULATION OF WATER, ETC.

UPON THE CIRCULATION OF WATER Theory and phenomena Tred-
gold's explanation and Hood's criticism and theory Actual cause of
circulation Variation in results Motive power Table for deter-
mining motive power. CONNECTING PIPES TO BOILERS Direction
of pipes Multiple flow and return services Disadvantages of hori-
zontal pipes Various simple forms of apparatus and their leading
features demonstrated The most practical method.

THIS subject claims the attention of all who are in the least
degree interested in hot-water works, as a knowledge in this
direction is of primary importance in their design, except,
perhaps, in cases where the apparatus requires to be of the
most ordinary and commonplace description, in which in-
stances the work is most usually left to workmen, who having
erected many such before, are able to copy their previous
undertakings without troubling to consider the reasons for the
success they may probably bring about. When, however,
the requirements are out of the common and some special
form of apparatus, or some unusual feature is to be carried
out, failure must, almost as a matter of course, ensue, unless
the designer is properly and well acquainted with the different
rules that govern the work, and particularly the phenomena of
circulation.

Hood goes to some length to explain and make this
subject clearly understood by the reader, and much profit can
be gained from his description. He first points out that
previous to his undertaking the task, Mr. Tredgold was the
only person who attempted to describe the cause of the cir-
culation of water, which he did as follows : " If the vessels
A, B (Fig. 4) and the pipes connecting them be filled with
water and the heat be applied to the vessel A, the effect of

Circulation of Water. 29

heat will expand the water in the vessel A, and the surface
will in consequence rise to a higher level a d, the former
general level surface being b b.
The density of the fluid in the
vessel A will also decrease in con-
sequence of its expansion, but as
soon as the column c d (above the
level of the centre of the upper
pipe) is of greater weight than the column />, motion will
commence along the upper pipe from A to B, and the change
this motion produces in the equilibrium of the fluid will cause
a corresponding motion in the lower pipe from B to A."

This explanation is far from being clear to the average
mind at first reading, but to put other words to what it is
intended to convey (with the hopes of making it more easily
understood, if possible) it has to be explained that in this
argument it is supposed that from the point c, which repre-
sents the centre of the upper pipe, to the point b, which
represents the normal ^/^/-water level (these two points are
represented in exactly the same position at e and b or e and /),
there exists a certain height of water, say 2 inches ; when
the water is heated in A, the expansion which takes place
increases this height of water by, say, another inch (to a d) ;
this 3 inches is then sufficient to outbalance the 2 inches at
the top of vessel B (viz. from e to/), and consequently forces
itself along the upper pipe in that direction, making a
proportion of water travel along the lower pipe from B to A.

This, perhaps, is a lengthy explanation devoted to what
Hood very correctly points out to be an erroneous theory
which will not account for the circulatory action in every case,
and he quickly explodes the matter by a description he gives
of an apparatus similar to Mr. Tredgold's illustration, but
which will not admit of the water rising above the normal cold-
water level when heat is applied, and which would not work at
all if the circulation depended upon the action described.
The apparatus in question is as Fig. 5, which it will be
instantly seen bears the closest resemblance to the other with

30 Warming Buildings by Hot Water.

the addition of an overflow pipe, and two stop-taps. The de-
scription, which is in every way clear and worthy of repetition,
is as follows : " Suppose the apparatus, Fig. 5, to be filled

with cold water and the two
Fig. 5.

y? stopcocks to be closed ; on ap-

" ~W c PI plying heat to the vessel A, the

B water it contains will expand
* ^J in bulk, and a part of it will
flow through the waste-pipe x,
which is so placed as to prevent the water rising higher in
the vessel A, than the top of the vessel B. The water which
remains in the vessel A, after it has been heated and a portion
of it has passed through the waste-pipe x, will evidently be
lighter than it was before, while its height will remain un-
altered. Suppose now, the two cocks/ g to be simultaneously
opened, the hot-water in the boiler A will immediately flow
towards B through the upper pipe, and the cold water in B
will flow into A through the lower pipe, although by the
hypothesis previously alluded to, unless the water in the
vessel A above the pipe centre C were heavier or rose to a
higher level than the water in the vessel B, no circulation
could take place, and in this case another explanation must
be found. The power which I consider explains this action
is, let us suppose heat to be applied to the boiler A, Fig. 5, a
dilatation of the volume of the water takes place and it becomes
lighter ; the heated particles rising upwards through the
colder ones, which latter sink to the bottom by their greater
specific gravity, and they in their turn become heated and ex-
panded like the others.* As soon as the water in the boiler
begins to acquire heat and to become lighter than that which
is in the opposite vessel B, the water in the lower horizontal
pipe d is pressed by a greater weight at z than at y, and it
therefore moves towards A with a velocity and force equal to
the difference in pressure at the two points y and z. The
water in the upper part of the vessel B would now assume
a lower level were it not that the pipe c furnishes a fresh

* See Convection, Chapter I.

Circulation of Water. 31

supply from the boiler to replenish the deficiency. By this
unequal pressure on the lower pipe, the water is forced to
circulate through the apparatus, and it continues to do so as
long as the water in B is colder, and therefore heavier than
that in the boiler A."

The writer has made this rather extensive extract from
the last edition, chiefly by reason of the argument being
so soundly dealt with, and were it put in other words the
ultimate amount of information imparted would have been
about the same. It is so very necessary to impress upon the
student that it is the superior weight of the colder water, and
this alone, that brings about the movement of the particles, and
ultimately the mass, of the liquid. It seems so natural to hear
it argued that it is the fact of the hot water being lighter than
the cold that brings about the circulation, whereas it is just
the reverse. A distinction without a difference, some may
say, but it is far from being so, as every practical man knows
how many errors are fallen into through considering the
ascending properties of hot water instead of the superior
descending force of cold water, when working out some
problem.

If we take a vessel of heated water (at any temperature)
that is not being subjected to further heat, we shall find that
it exhibits exactly the characteristics of cold water. So far
as movement is concerned the particles will remain at rest if
the vessel is not shaken, and it will be seen that the water has
no tendency to rise, not any particle of it, yet from the very
generally accepted notion that hot water has the power of
rising, we might almost expect that the vessel would have to
be sealed at the top to prevent it escaping.

If the vessel of hot water just referred to has some cold
body placed at the top, a piece of cold metal or ice for
instance, so that the upper stratum of water is cooled, a circu-
lation will instantly set in (similar to that which would ensue
if heat were applied at the bottom), as in this case we cause
cold particles to be above the heated particles, and this being
contrary to the laws of gravity the former by their superior

32 Warming Buildings by Hot Water.

weight displace the latter and find their way to the bottom,
leaving a fresh supply of warm particles to come in contact
with the cold object, to be cooled and sink in their turn, and
so on. This perhaps will give a clearer idea of how it is that
the circulation of fluids is due to the superior weight of the
cold particles, and not to the lightness of that which has been
heated. It is simply the result we get when we place different
substances in the pans of a pair of scales : the pan which
contains the greater weight sinks, and that with the least
weight rises, not because the lighter article has any inclination
to rise, but because it is impelled by the superior force out-
balancing it.

This difference in the weight of two columns or bodies of
water, causing movement in opposite directions, has been
designated the " motive power " of the circulation, a name
which is of course strictly correct, yet does not at first sight
give a very good conception of its meaning. Hood has
set out a scale or table showing theoretically the speeds
obtained in circulation by certain differences in temperature,
which table will be quoted directly ; but it is next to impos-
sible to set up a standard for practical purposes, owing to the
ever varying conditions that are met with, no two apparatuses
working under the same circumstances, and even one apparatus
will not give exactly the same results always, as it maybe
influenced by changeable external conditions. This will show
what a difficult task it would prove to any one to compile any
reliable information in this direction ; and even if it were
possible its adoption would not be general, as the speed of
circulation does not always govern the success of an under-
taking, although as a rule it is considered that an apparatus
is well designed and erected when all the pipes and radiating
surfaces are at a high temperature soon after the fire is started ;
but this would be due chiefly to the size and power of the
boiler, the skill of the attendant, and to some extent, the
quality of the fuel, and also whether the pipes were in a
temperate or very cold situation, and several other circum-
stances, as will be learnt presently.

Circulation of Water.

Perhaps the greatest drawback to the adoption of any
table of this kind would be its difficulty of application. In
the first place it would be necessary to complete the erection
of the apparatus in every part, then charge it, and when
this was done it could be very easily tested in the ordinary
way to see if it fulfilled the designer's expectations, and gave
the desired temperature. If it did this no further trouble
would be needed, whereas if we tested the speed of the circu-
lation and it proved satisfactory, it would by no means
indicate the success of the work, as it would not tell us if there
was sufficient pipe or radiating media, nor would it tell us if
the pipes were well placed, in fact it would prove misleading.

In dwelling upon the non-practical utility of the table
referred to, it is with no desire to underestimate its value in
other ways, and apart from its scientific use it is desirable
information to impart as showing exactly what constitutes
motive power in hot-water circulation.

DIFFERENCE IN WEIGHT OF Two COLUMNS OF WATER, EACH ONE FOOT

HIGH, AT VARIOUS TEMPERATURES. (Hood.)

Difference in

Temperature of
the two Columns

Difference in Weight of two Columns of Water contained In different
sized Pipes each ONE FOOT in height.

of Water, in

j r

Fahrenheit's
scale.

i in. diam.

z in. diam.

3 in. diam.

4 in. diam.

Per square inch.

grains.'

grains.

I'S

6-3

I4'3

25^

2-028

3'I

12-7

28'8

5I-I

4-068

4*7

19-1

43'3

7 6- 7

6-108

6-4

25-6

57'9

I02-5

8-160

8-0

32-0

72-3

I28-I

ICT2OO

9-6

38-5

87-0

I54'I

12*264

II-2

45 'o

101-7

180-0

14-328

12-8

5 J *4

116-3

205-9

16-392

14-4

57*9

131-0

231-9

I8-456

16-1

64*5

i45'7

258-0

20-532

The above table, on account of its accuracy, may well be considered a testimonial
to the exceeding care exercised by Hood in compiling his data.

34 Warming Buildings by Hot Water.

The above table has been calculated upon the difference
in the temperatures of from 170 to 190, these two tempera-
tures being about the heat that is obtained in a well-con-
structed apparatus when in full work.

This table, it will be noticed, gives the difference in weight
between water at two different temperatures per foot in height,
so that in arriving at the actual motive power exerted in an
apparatus, we must take the height from say the centre of the
return pipe, where it enters the boiler, to the top of the flow
pipe, where it ceases to travel vertically
Fi s- 6 - as at a, Fig. 6. This distance varies from

^. 3 a few inches to three or four feet in

^ common horticultural work ; taking an
apparatus of an ordinary kind we will sup-
pose this distance is three feet. We next
have to ascertain the temperature of the
water that enters the boiler from the re-
turn pipe, and that which leaves the boiler
by the flow pipe, both temperatures to be
taken at points as near to the boiler as possible. Supposing
the pipe to be 4-inch, and the difference to be 16, we get
from the foregoing table 205 grains per foot, x 3 = 615
grains = \\ ounce, and this weight, which will strike the
reader as being exceedingly trifling, constitutes the motive
power of the circulation in an apparatus. This very small
difference in the weights of the water is, however, under
ordinary circumstances, capable of setting up a tolerably rapid
movement, notwithstanding that in the average apparatus
there may be as much as 210 gallons = 2100 pounds of water
to be made to circulate. In water, fortunately, we have a
material peculiarly adapted to this purpose, as owing to its
perfect mobility, friction does not play a very important part
in its passage through the pipes ; if it did, failure would
be inevitable.

From the results just explained we gather two points of
importance : first, that by increasing the difference in tempera-
ture of the water entering the boiler by the return pipe, and

Circulation of Water. 35

that leaving the boiler by the flow pipe we shall obtain an
increase of motive power (i. e. the speed of circulation) ; and,
secondly, that the more we can carry the flow and return pipes
in a vertical direction, the faster will the water circulate, with pro-
portionately better results. When an apparatus is first started
(by applying heat to the boiler), the results are quickened by
the fact that a considerable difference in temperature exists
between the water entering and that leaving the boiler just at
this time, as all the water passing in from the return pipe is quite
cold ; but after the whole is heated up a less difference exists,
but the water continues to circulate at about the same speed,
owing to some extent to the impetus given it. It does not
always follow that the more the fire is urged the greater the
speed of circulation, as although the water will leave the
boiler at a higher temperature (and diffuse a greater heat), yet
it will return into the boiler at a higher temperature also, so
that the difference in gravity between the two columns
remains almost the same.

It is most wonderful to note what an exceedingly low
degree of heat will bring about movement amongst the
particles of water. In any of the simple forms of apparatus
already referred to, it will be noticed that particles of water
commence to rise almost instantly the heat is applied, hardly
allowing time for the heat to pass through the substance of
the vessel, and when once the circulation is established, many
particles will be noticed flying upwards at a velocity that
could scarcely be followed with the eye if the water was not
confined to such a small space. This bears out the theory
that not only is there an absolute want of cohesion amongst
the molecules, but there must be a repelling influence exerted,
otherwise how could such an extraordinary absence of friction
be manifested ?

In considering the small amount or value of the power
that produces a circulation in such a large bulk of water it
naturally brings to mind, as Hood very wisely points out,
that a trifling obstruction or error in workmanship must have
a very prejudicial effect, or probably ruin the efficiency of the

D 2 '

36 Warming Buildings by Hot Water.

work. But it is rather unusual to hear of such failures ; that is,
they are very small in number compared to the successes,
notwithstanding that there are about as many such under-
takings working with a low motive power (nearly all horti-
cultural works) as with high. With careful, i. e. thoughtful
workmanship and attention to the rules laid down, success
nearly always ensues as a matter of course.

CONNECTING PIPES TO BOILERS.

One of the most necessary rules to be observed in hot-
water works is, as to the point at which the flow pipe is
connected into the boiler. From what we have learnt of the
action of convection \hzflow pipe should be connected up at
the top of the boiler in readiness to convey away the heated
particles of water in the direction required ; but merely con-
necting this pipe at a high point is not sufficient, it must be
connected at the very highest point, as at Fig. 7 for instance.

Fig. 7- Fig. 8.

The reason for this may not be apparent to the uninitiated,
and it is therefore necessary to explain that supposing the^ze;
pipe to be connected at some lower point, as at Fig. 8, we
should then be unable to expel all the air from the boiler.
In other words, we could not fill the boiler with water above
the top of the flow pipe, as shown, as unless the air be
expelled, we cannot get water to enter, for both air and water
cannot occupy the same space at the same time, and this
accumulation of air will prove a great obstacle to the free
circulation. Now if we placed an air cock at the point

Circulation of Water. 37

marked a, we could quickly dispose of the air for the time
being, and get the boiler quite full of water, but it would only
give temporary relief, as water, particularly in cooling, readily
absorbs air, and when heated parts with it again, and the air
may always be looked for at the highest points, and conse-
quently this air cock would require fairly constant attention.
If, on the other hand, we put an air pipe at the point a, the
difficulty experienced by air collection would be overcome
(this pipe having an open end above the level of the supply
cistern), except that it is against all recognised principles to
start the flow pipe horizontally if the work is of any magnitude ;
for small works it is permissible (see the Loughborough boiler).

After starting the flow pipe from the extreme top of the
boiler,* it should be continued in a vertical direction as far as
it is possible, so as to favour the motive power to the greatest
extent, although in many horticultural works there is often-
times only room for a few inches of vertical
pipe, a bend having sometimes to be placed Flg * 9 *

directly on the boiler, as Fig. 9.

All the vertical pipe in an apparatus
goes to increase the motive power and the
consequent quicker results ; that is to say,
if the pipe rises one foot from the boiler
before it is carried horizontally, and then it
rises another foot and then another, we can
calculate upon having three feet of vertical
pipe, although it is not all immediately near the boiler. All
vertical pipe aids in increasing the circulation ; horizontal
pipe does not aid in the least wherever it is situated ; in fact,
it is the reverse, owing to the friction it involves, and all
matter, sediment, &c., collects in these pipes.

In many apparatus it is found desirable to have two
and even more flow pipes. This can be done with every
satisfaction, and the writer is rather in favour of this arrange-

* If it is a wrought-iron pipe screwed into the substance of the boiler,
the pipe must on no account be screwed right through so as to project
inside, otherwise the objectionable accumulation of air must ensue.

38 Warming Buildings by Hot Water.

ment, where it is convenient, and the circumstances make it
desirable, in preference to the one flow pipe and its many
branch services.

The position in which the return pipe enters the boiler is
not so important as the flow pipe, but at the same time it
should not be brought in anywhere. The usual and correct
place to bring it in is close to the bottom of the boiler, situated
about centrally from front to back, as Fig. 10, but a system

Fig. 10. Fig. ii.

that is at all extensive has usually two returns (although but one
flow), and this practice is to be highly commended as equalis-
ing the action in the boiler, and it also reduces the likelihood
of fracture of the boiler plate.*

The flow pipe, which, as we have already explained, starts
from the top of the boiler, is taken vertically as far as possible,
and then t it is usually continued at right angles, i. e. hori-
zontally ; but every practical man tries to give the horizontal
pipe a slight rise where at all possible, if only an inch or two
in fifty feet, as there is then a natural inclination for the water
in the return pipe to aid in the motive power ; and though

* It is found that with very many boilers that are taken out fractured,
and which have only one return pipe, the fracture has occurred on the side
opposite to that where the return is connected, as shown at Fig. n, the
fracture being due to an accumulation of sedimentary deposit at this point
which has kept the water from having free contact with the metal, thus
ending in the destruction of the fibre by the heat. This deposit could not
have occurred just there had there been a return pipe at that side. The
fracture shown is exaggerated as to size, and marked a.

\ We shall deal with horticultural work first, and speak of the domestic
systems, pipes or coils, in which a great deal more vertical pipe is obtain-
able, presently ; but the same general principles apply to .both.

Circulation of Water. 39

the inclination be trifling, it is better than a perfectly hori-
zontal pipe in which we may suppose the water remains quite
inactive unless propelled by another force. This gradual rise
is continued to the farthest limit of the apparatus if possible,
as in Fig. 12. It may be mentioned that it is usually possible

Fig. 12.

to do this if care be exercised in planning the work, and as
every glasshouse for horticultural purposes has, as a matter
of course, to be heated, the builder (who may also do the hot-
water work) arranges the structure to the best advantage,
putting the boiler pit at the lowest point ; and where there are
a series of houses it is very advantageous if they can be put
on slightly rising ground so that each house is some inches
higher than the preceding one.

There is an idea rather prevalent, especially amongst work-
men, that it is necessary always to keep the flow pipe above
or over the return as shown at Fig. 12. This is not really
necessary, although preferable, but it is not always convenient
and sometimes hardly possible, and when pipes are carried in
shallow trenches or laid beneath gratings it is commonly
necessary to lay them flat side by side. If, however, it is
required to carry them along the side of a wall, then they are
placed one above the other, but if there were more than two
pipes it might occasionally prove awkward to connect any
branch services required. In any case if the flow pipe rises
to a certain height above the boiler the motive power will be
the same whether it be carried above the return or whether
they be carried side by side, or in other words, either arrange-
ment will prove equally satisfactory under similar general
conditions.

40 Warming Buildings by Hot Water.

There can occasionally (though rarely) be met with an
apparatus in which the return-pipe is brought back over the
flow as at Fig. 1 3 ; this is, according to general supposition,

opposed to good principles,

Fi s- J 3- and the general verdict

would be that the apparatus
was the result of employ-
ing insufficiently skilled
labour, as possibly might be
the case, but whatever com-
ments might be passed,
the apparatus (if all its

other features are favourable) will be found to work satisfac-
torily, and this should be sufficient to silence opposition.

Now in an apparatus as illustrated, the flow pipe will act
as a flow pipe * up to the point marked a (supposing the
pipes have a gradual rise to this point, as should always be
the case if any way possible, as before explained), and from
this point the water will commence to fall (constituting it the

Fig. 14.

" return ") and by its gravity produce the needed circulation.
Now in this case we get exactly the same length of hori-
zontal and vertical pipe in the return as if the apparatus were
constructed as at Fig. 14 (which is a copy of Fig. 13 with the
position of the pipes altered) ; consequently exactly the same

* It sometimes seems difficult to fix the point in an apparatus where
the flow pipe terminates and the return pipe begins, especially as one is
merely a simple continuation of the other ; but it is usual to consider the
flow pipe as extending from the top of the boiler to the highest point in the
apparatus, and from this highest point the continuation of the pipe is con-
sidered to be the return even in a form such as Fig. 20.

Circulation of Water. 41

results are obtained practically, and in theory we may expect
results of a little better nature owing to the whole of the
vertical portion of the return pipe being near the boiler, as
will be understood directly.

It is not by any means intended to recommend this
arrangement of the pipes in preference to the customary
method, for in the first place the difference in actual results
would not be appreciable, nor could it be detected at all except
in a very large undertaking, and then only to a trifling extent,
and to advocate such a change for practically no benefit what-
ever would be useless and would lead to endless trouble
and confusion amongst workmen. This unusual arrangement
is merely described to show that were it necessary it might be
carried out without hesitation ; even a branch service from an
ordinary apparatus could be so carried if particularly con-
venient.

In support of our view of the importance of having the
whole of the vertical portion of the return pipe as near to
the boiler as can be arranged, we cannot do better than
quote Hood's words, on account of the very lucid manner in
which he deals with this much disputed question.* He says :
" As the water in the pipes is constantly parting with its heat
both by radiation and conduction, while that in the boiler is
as continually receiving additional heat from the fire, an
equality of temperature never can occur ; consequently, as
the circulation is caused by the water in the descending pipe
being colder and therefore heavier than that which is in the
boiler, it follows, as a necessary consequence, that the colder
the water in the descending pipe shall be relatively to that in
the boiler, so much the more rapid will be its motion in the
pipes. In an arrangement of pipes as Fig. 15 the water in
the descending pipe c d having to come a greater distance

* This question is very much debated even at this present time, and
even by those who profess to be authorities upon the subject, but who, it
must be inferred, lack some of the more preliminary knowledge necessary
in discussing the matter. The theory established by Hood 'is strictly
correct in actual practice, and can be relied upon.

T7SI7BRSIT7

42 Warming Buildings by Hot Water.

before it descends to the lower part of the boiler than when
the pipes are arranged as Fig. 16 ; it will of course be colder
at the time of its descent in Fig. 15 than Fig. 16, and there-
fore the circulation will be more rapid."*

Fig. 16.

It will be seen very clearly that the water in the descending
pipe (which is furthest from the boiler) in Fig. 16 must
necessarily have hotter water in it than when the water has
to travel a still greater distance before it descends, as Fig. 15,
and has therefore lost more of its heat. This can be shown
still more clearly by spacing off the pipe and supposing that

Fig. 17.

175 170 165 160

1 .,

[125 130 135 14-0

WS ISO

the water, by radiation, &c., loses five degrees of heat in
traversing each length of space so marked. In Fig. 17 we
will suppose the water starts from the boiler at 200 and

* As Hood remarks, it is very necessary, when studying this work,
to avoid the erroneous hypothesis that the motion of the water commences
in the upper pipe instead of the lower one.

Circulation of Water.

returns into it at no ,* the water losing five degrees of heat
each space it passes through. Now let us also suppose that
for each five degrees of temperature lost there is an increase
of weight of 20 grains, we can then see almost at a glance
that in Fig. 17 the water when it reaches the descending pipe

Fig. i 8.

130 IBS 180 175 170 165 160

155

r n

-ISO

125 130

will be 300 grains heavier (for a given bulk) than when it
issued from the boiler, whereas in Fig. 18 it will be but 170
grains heavier and so proportionately less in motive power.

Fig. 20.

Figs. 19 and 20 show two methods of which there will
occasionally be found advocates who contend that better
results are obtainable by these arrangements than if the work
is carried out in the ordinary way.

It should be first mentioned that only in a simple form of
apparatus could either of these methods be adopted, as any

* These are, of course, supposed temperatures.

44 Warming Buildings by Hot Water.

system of branch or secondary services would be almost
impossible unless the circumstances happened to be just
favourable. With Fig. 19 the contention is that instead of
carrying any portion of the return pipe horizontally, which is
of no assistance to the motive power, the return should be
made to slope down all the way, commencing at the termina-
tion of the flow pipe, and ending at the boiler, as shown, so
that the water commences to exert its downward force from
beginning to end of this pipe, no portion of the pipe being
valueless as regards assisting in the motion of the water. This,
it must be admitted, makes up a very fair case for the advo-
cates of the method, but upon analysis it is very weak, and
the method recommended (Fig. 17) will give the best results
practically as well as theoretically.

If we space this apparatus off as we did the last, we
shall find that in the return pipe we have an average tempera-
ture of 135, which, according to the method adopted, repre-
sents water having a gravity superior to that just leaving the
boiler by 260 grains. Now, although the return pipe of this
apparatus slopes a long way, the actual fall it has is no more
than in Fig. 17, so that to get comparative results in each
case we must take the average temperature of the water in
the return pipe of each system (not allowing horizontal pipe
to enter into the calculation in either instance), and that
which shows the least temperature has the greatest motive
power, as in each case we show the water leaving the boiler
at the same heat, viz. 200.

In the apparatus now being described we get an average
temperature of 135 in the sloping return pipe, representing
an increase in weight of 260 grains, as already stated. If we
take the average of Fig. 17 (the style of apparatus most
recommended), we get an average temperature of 120 in the
active part of the return pipe, and this represents an increased
weight of 320 grains,* which it only remains to be added

* It is desirable to again remind the reader that these temperatures
and weights are purely supposititious, although not such a great way from
those actually found.

Circulation of Water. 45

conclusively proves that it is a more efficacious arrangement
than that with the sloping return as in Fig. 19.

This plan of sloping the return pipe in the manner shown
would give better results than erecting the apparatus as at
Fig. 1 8 ; in fact it would be equal to putting the descending
portion of the return pipe half-way between the boiler and
the termination of the flow pipe, as Fig. 21.

Fig. 21.

Apart from the question of effectiveness, this method has
hardly ever been adopted, owing to the trouble that must
necessarily ensue when an apparatus is not confined to a few
straight lines of pipes.

In Fig. 20, which Hood illustrates and very clearly
explains, we should get worse results than with any method
yet explained ; yet, strange to say, there are a good many
people who, if not quite positive, are quite ready to give an
opinion in favour of having the flow pipe commencing to descend
immediately after it leaves the boiler, the contention being that,
by making the pipes almost wholly the return service, the
motive power will be aided proportionately. This argument,
however, is not sound, as in the first place, although the flow
pipe is not continued to the further end of the apparatus, yet
what we may call the active part, i. e. the ascending column
of the flow pipe, is not disposed of, and, as explained with the
last method, the sloping pipe, although perhaps extending a
long way, has only an actual fall of two or three feet, and this
fall takes place where the water is of least weight, so that by
the method used in calculating the results obtained in the
other systems, we shall find that the effect obtained is the
same as constructing an apparatus as Fig. 22. There is but
one way of making the system less effective (without wholly

46 Warming Buildings by Hot Water.

destroying its efficiency), and that would be to make the
apparatus as this last illustration, but with the descending
pipe still closer to the boiler. Any one of the methods dealt
with will work that is to say, the water will circulate within

Fig. 22.

them, and in a small apparatus such as we should erect in a
greenhouse, it is doubtful if any difference in results would
be perceptible ; but in an undertaking of even a moderate
character, a deal of trouble might arise with the less efficient
methods, as not only does the apparatus require to be working
at its best, with the least expenditure of fuel and labour, but
with the increased quantity of pipe and its ramifications, a
greater resistance is opposed to the motive power, which, if
not great, might be actually nullified, for we have seen that
in horticultural works, which are very dwarfed as to height,
the circulation is the result of but a few ounces difference in
weight of the entering and outflowing water at the boiler,
under favourable circumstances. The principle described
under Fig. 17 is considered and been found the best, both by
theorists and practical workers.

( 47 )

CHAPTER III.

V .

AIR IN PIPES SUPPLY OF WATER EXPANSION OF PIPES.

AIR IN PIPES. Accumulation and dislodgment Air pipes and cocks
Stoppage of air vents. WATER SUPPLY. Provision to replenish loss
by evaporation, also when water is drawn off Expansion of water by
heat Capacity of supply cisterns Overflow Position of cistern
Service pipe and connections Rain or hard water Sediment or lime
deposit Useful appliance for small purposes Flushing and cleansing.
EXPANSION OF PIPES. Provision for expansion Measure of expan-
sionPipe bearings.

THE preceding chapter has only dealt with the most
elementary forms of apparatus, yet before proceeding to
describe those which may have necessarily to be executed a
little differently from the customary way, and to what extent
such variations can be carried, it is necessary to speak of a
subject which plays an important part in the execution of
these works, and which should be explained before going
further. This is the dislodgment of air from the pipes, a
collection of air at some unexpected point being one of the
most prolific and annoying sources of trouble and vexation
possible, owing to its so effectively impairing the circulation.
And we must also deal with the means adopted to supply the
apparatus with water, particularly to make good the loss by
evaporation, or any that may be drawn away.

When an apparatus is newly constructed, the boiler, pipes,
and all appurtenances are, of course, filled with air previous
to their being charged with water, and when the water is
admitted, the air is driven to the highest point, where it will
persistently stay, whether the pressure of water be high or
low, and most effectually prevent the water circulating. We
cannot, as some have supposed, by any means make the air
quit its high position and descend, and so escape by the

48 Warming Buildings by Hot Water.

supply pipe ; not even if we get the water to circulate can we
get it to carry any accumulation of air, however small, down-
wards, consequently a means has to be provided in the shape
of a cock or small open pipe to allow of the free escape of
collected air, not only when first charging, but afterwards, as
the water is by the fluctuation of temperature continually
absorbing and expelling air.

In a simple apparatus, as Fig. 23, the water in the two
pipes would be effectually prevented from having contact, as
shown, if no air outlet was provided, but with a pipe or cock
at a, the trouble is instantly overcome.

Fig. 23.

Of course it is easy to suppose that the fixing of the
points for the air vents is a simple task, owing to the air
finding the highest position due to its being so many times
lighter than water. But this is not exactly the case, for in
the ramification of an extensive system it is not at all an
unusual thing for some point to be overlooked, and so cause
trouble until remedied, and the remedy sometimes partakes
of the nature of a problem, as will be learnt presently. If we
get a horizontal flow pipe of any length (which fortunately
is rarely required, as a rise, however little, can usually be got) ;
the air will collect in great bubbles at irregular points along
its whole length, whether this pipe be the highest one, or
whether it is only one of a series, and in this case it would be
desirable to have two or three air vents along the pipe when
first charging, as the air globules do not move when the water
circulates (they would if the pipe had a rise) ; but remain in

Air in Pipes.

their positions most tenaciously, the water, when circulating,
passing under, as Fig. 24. This can be ascertained only too
quickly in any model or experimental apparatus.

The most simple (but generally most expensive) and by
far the best air vent is an open pipe. This may be in iron,
copper, or composition

tube ; in size it varies from Fig. 24.

\ inch to f inch, but both
these are extremes. As
air can escape from an
aperture with exceeding
rapidity, it is not neces-
sary to have a large tube, and accordingly | inch and J inch
are the two sizes commonly used ; if the latter, it is the iron
gas tube that is most usually employed ; but with the former,
copper tube generally takes its place, as this can be readily
bent, and the small quantity required makes but a small
difference in cost.

Composition tube (a soft metal tube commonly called
"compo") is inexpensive, and readily bent to any desired
angle ; but its softness is objectionable, as being so readily
injured and disfigured by trifling mishaps, and as an air pipe
is commonly a conspicuous object, its appearance must be
considered. This is another reason for using copper tube,
and a further reason why the pipe should be
of limited size.

Air tubes, especially when they have two
or three bends in them, may sometimes be-
come stopped by dust and debris, assisted by
cobweb, and for this reason, although an J-inch
pipe would give free vent to the air, it is not
desirable to use it. To prevent a stoppage
as much as possible, it is a good practice not
to leave the pipe pointing upwards, but
turned over either as Fig. 25 or Fig. 26, and to facilitate
removal, when they require cleaning, a union should be
used to connect this tube with the hot-water pipe.

Fig. 25. Fig. 26.

Warming Buildings by Hot Water.

Fig. 27.

One very important feature connected with these tubes is
that they must not on any account dip downwards, that is to
say, like the flow pipe of a hot-water apparatus, they must
either be vertical, or ascending to some degree a horizontal
pipe being hardly tolerated, and an air pipe that descends in
the least degree being utterly wrong. If we carry an air

pipe downwards at any point,
as at Fig. 27 for example, this
pipe may be quite clear, and
fulfil the duties of an air vent
properly when first the apparatus
is charged ; but after the appa-
ratus has been in use a short
time, water will collect at a,
by condensation of vapour (and
in time a collection of dirt par-
ticles will also be found there),
and this small quantity of water

will effectually prevent the free exit of any air that may
collect afterwards, as we have to remember that there is no
pressure exerted to expel the air, unless the boiler be over
fired and generate steam. It is practically the same effect
as is obtained by putting a trap in a bath waste pipe, this
trap holding a small quantity of water to prevent the exit of
objectionable gases, which it does successfully a success which
has objectionable qualities in the air pipe of a hot -water
apparatus.

No portion of an air pipe which contains water must be
carried outside, or it will be seriously affected by frost. An
air pipe cannot conveniently be used with an apparatus that
extends through several floors of a building, owing to the
great length some of the pipes would have to be,* and resort
has then to be made to a tap or cock.

* There has to be an air vent to every distinct service and to every
coil, radiator, &c., so that in an extensive apparatus of this character
twenty or thirty vents might be needed ; but so many as this are rarely
needed in the low-lying horticultural class of work.

Air in Pipes.

An air cock is usually of a shape similar to Fig. 28 (full size),
which has an internal construction very much like an ordinary
tap, but the " way " or passage through it is only about \ or
T 3 ^ inch in diameter, which, however, is ample for the purpose,
as these are things that cannot get stopped up in any

Fig. 28.

Fig. 29.

way like an air pipe. The screw portion is commonly made
to fit into a hole which is drilled and tapped for J-inch gas
thread (pipe). A more improved form of cock has been quite
recently introduced, as Fig. 29 (full size). This form is a de-
cided improvement, being less subject to leakage from wear and
use, and less likely to stick tight ; and the makers claim that as
the nozzle is situated at the side, there is less likelihood of
damage being done when turned on, if it is in proximity to
any wall or other decorations.

When an air tap is opened (i. e. turned on), if there is any
air, it escapes ; but we can never tell if the whole of the air
has escaped until water issues, and if there is any pressure the
water will be ejected to a considerable distance, oftentimes
wetting the ceiling if an upright air cock is used, as Fig. 28.
The other form of cock, Fig. 29, is supposed to overcome this,
as the outlet is at the side ; but it must be submitted that if
the ceiling escapes injury, the water may still be projected
against a wall ; but with either form of cock this trouble
can be overcome by holding a cloth, or some such substance,
over the tap when discharging the air.

E 2

5 2 Warming Buildings by Hot Water.

There are two forms of automatic air vents to be had ; but
although such appliances are much needed, the writer hesitates
to recommend them, owing to the bare possibility of their
failing at some time, early or late, which
Fi g- 3- failure would be almost a calamity in

some instances ; as should it for instance
be in a radiator situated over a valuable
ceiling, the leakage would in a few
moments do some harm ; or in a grape
house the possible flood of water might
ruin the vines, which need a dry atmo-
sphere, besides causing an instant fall in
the temperature, which, if occurring in the
night, would work endless mischief in any
horticultural building.

SUPPLY CISTERNS, ETC.

It is, of course, necessary to pro-
vide some means not only of filling a
hot-water apparatus in the first place, but also of replenish-
ing the waste of water that takes place from evapora-
tion, and that which may be drawn off, if a means of
drawing water off is provided. Between an apparatus that
loses water by evaporation only and one that has water drawn
from it as well,* some difference may exist in the provision
for replenishing, and it will be best to speak of each separately,
the latter arrangement being taken first.

In this case a supply cistern has to be provided, this
cistern being very commonly of cast iron, either plain or
galvanised, and its size requires to be governed by the magni-
tude of the apparatus in the following way :

Water expands, i. e. increases in bulk, upon the applica-
tion of heat, the expansion uniformly increasing as the tem-
perature rises, so that a vessel exactly filled with cold
water would, when heated, overflow ; therefore if a cistern of

* The writer is still alluding to horticultural work, in which a deal of
warm or tepid water is required for watering melon and cucumber pits,
and for many other purposes.

Water Supply. 53

insufficient size were provided, it would not be capable of
holding the increased quantity or margin that has to be
provided for when the water is heated.

Water, when heated from freezing to boiling point
expands one twenty-fourth that is to say, twenty-five gallons
of boiling water equal in weight (and original capacity) twenty-
four gallons of water at freezing point ; or in other words,
water near freezing point occupying 24 inches space in a
vessel, would, upon being heated to 212, be found to be
occupying 25 inches. But in hot- water works we have no
occasion to make provision to this extent, as the two
extremes of heat named are not experienced, and the
calculation need only be based upon a difference of about
130, that is from 50 to 1 80, which, according to the above
result, would give us an increase in bulk of about one in
thirty-six ; so that by using a cistern having a capacity of one-
thirtieth of the whole contents, we shall allow room for
expansion, and have a little room to spare, which is needed,*
especially as the pipes, &c., are also affected by heat, and the
slight increase in size that they undergo enables them to hold
a little more water.

It is a very desirable plan to fit these supply cisterns with
an overflow pipe, this overflow being conducted to some non-
objectionable point, and it is requisite when charging an
apparatus not to fill the cistern more than an inch or two,
otherwise an overflow will take place as the water heats. The
ball valve (if one is used) requires to be fitted near the
bottom.

The quantity of water that is lost by evaporation only is
very trifling, perhaps a quart per week (according to the size
or heating properties of the apparatus), and if none is drawn
off, a ball valve to automatically replenish the loss is not

* See table at end giving capacities of pipes, &c. As an instance, 500
feet of 4-inch pipe and the boiler would contain about 280 gallons. This
divided by 30 gives 9i gallons, which represents the least capacity the
cistern should have, unless an overflow of water is unobjectionable, or
unless the overflow pipe of the cistern is of good size and relied upon to
take away the surplus water (see page 56).

54 Warming Buildings by Hot Water.

necessary, and is sometimes fruitful of mischief, as these
articles are ever ready to refuse to act when they have little
work, and get stiff in the working parts. When water is
drawn off for any purpose whatever, it is very desirable and
necessary to have a ball valve or cock ; but care should be
exercised to get one of a good quality, as a really perfect
article of this description has not been made yet.

The position in which the supply cistern should be fixed
is governed to some extent by circumstances, but it is
usually placed as near the boiler as possible, but there may
be no objection to its being at the further extremity if desir-
able. There is something of a controversy existing amongst
workmen as to whether or not an advantage is gained by
carrying the supply service into the boiler itself instead of
into a pipe ; but there is no strong argument in favour of this,
in fact there is a greater likelihood of the water in the cistern
becoming hot by this means. The best arrangement by far,
and which is adopted by all the leading specialists, is to
connect the cold supply service into the return pipe, this
service (cold supply) either dipping down below the return
pipe before entering it, as Fig. 30, or having what is called a
"siphon," in reality a double bend, as Fig. 31, to prevent the
hot water circulating up it, as it would do readily if the pipe
proceeded straight from one point to the other.* Some

* In this we have illustrated a phenomenon peculiar to the earliest form
of hot-water apparatus in which but one pipe is used. In this arrange-
ment the pipes could never be allowed to dip down to the slightest extent
under any circumstances without entailing a marked failure. Each pipe,
whether there were many or only one, was a flow and return in itself. If
vertical, the heated water ascended up the centre of the pipe, and the cold
descended around close to the outer surface. If they were carried in a
slanting direction, the hot water travelled along the upper half of the pipe,
the cold travelling back beneath it. It is worth any one's while testing this
with a glass tube apparatus as already referred to, as the action is very
peculiar, showing again how very free from friction the water particles
are which allow of contrary currents travelling alongside in contact
with each other, yet absolutely free from the least trace of resistance.
If this single pipe is carried horizontally or nearly so, the water does not
circulate. To dip the pipe in the least degree is to keep it more still if
possible.

Water Supply.

prefer to adopt both measures, as Fig. 32, and as the extra
cost is but trifling, it is much the best plan.

The cistern need never be fixed higher than from 12 to
24 inches above the level of the highest point in the flow

Fig- 3i-

Fig. 32.

pipe, so that the apparatus may quite fill. No more than this
is required, as increasing the height of the position that
the cistern occupies only adds to the strain upon the appa-
ratus by the increased pressure of water. This will be more
fully explained presently, when speaking of those forms of
apparatus that are used for heating several floors of a building,
and in which the question of pressure must have every con-
sideration. The supply pipe (from the cistern to the return
pipe) should be either f inch or I inch, the latter for pre-
ference, as a great deal of sedimentary deposit occurs. It
is an excellent plan to have a screw plug at the bottom point
of the double bend, as dirt may accumulate here very quickly.
It must be mentioned that when water is drawn off for
various purposes a new and objectionable feature commonly '
presents itself, if the water be hard (by coming from chalk
strata), in the fact that the boiler gets incrusted inter-
nally with a coating of carbonate of lime, which, when of

56 Warming Buildings by Hot Water.

sufficient thickness, will cause the boiler plate to become
fractured. This takes place in a minute form with nearly
every apparatus (unless rain-water be exclusively used, as
is always recommended), but no appreciable deposit shows
itself unless the water is often changed, as each quantity of
water, when subjected to heat, deposits a certain quantity
of lime, which, although small, quickly forms a thick coating
on the boiler plate when fresh water is frequently entering the
apparatus. This subject will also be treated fully presently
under the heading of " Hot Water Supply " (for baths and
household purposes).

When no water is drawn from the apparatus a ball valve
is not usually employed, owing to this article being apt to get
out of order unless it has regular use, and it is not always
that the rule as to the size of the cistern being governed by
the capacity of the apparatus is adhered to ; as although the
water expands when heated to the extent described, yet it
only expands when first heated, and does not contract until
the water is allowed to cool, which will be probably an
interval of six months at least, so that in many cases a small
cistern is put just for filling purposes. The water, when
first heated up, is allowed to overflow (passing away through
the overflow pipe) as much as it will, after which no trouble
is experienced until it is next charged full with cold water,
which certainly does not happen in the winter, and if a
forcing house is in connection the fire is then kept going all
the year round.

For a simple apparatus consisting only of a few lines of
pipe a very useful appliance is obtainable, which fulfils the
purpose of a supply cistern and air vent combined, besides
acting as a support and junction piece to the flow and return
pipes. This article is as Fig. 33, which shows its application
clearly. It is a very useful contrivance.

Rain-water is most commonly used for charging the
apparatus ; but although it is the best, as creating no incrusta-
tion of lime deposit, however much the water may be drawn
off, yet it is not always obtainable ; and when it is, it cannot

Expansion of Pipes.

Fig- 33-

Fig. 34-

be got quite free from dirt, and through a little carelessness
the circulation has often been stopped by leaves, &c. It is
also noticeable that soft water has a much more vigorous
action upon iron than hard, causing it to rust very rapidly.
For these reasons it is very necessary to provide
a means of emptying the apparatus by a pipe or
tap fixed at a low point, so as to periodically
flush out all sedimentary matter. This should
be done regularly, and at least twice a year,
otherwise the deposit quickly becomes suffi-
ciently solid to prevent its being removed by a
flush of water, and it will then become necessary
to take the pipes apart to clear them. The
writer once saw a long length of pipe more
than half filled with deposit caked hard, as Fig.
34. This accumulated by about three years'
negligence.

The expansion brought about by an increase
of temperature has been spoken of so far as it
concerns the water that fills the apparatus, but
we have also to consider its effect upon the iron pipes, &c.,
which contain the water, as these, and practically everything
else in nature, are subject to this phenomenon. Although
the increase is exceedingly minute in a single length of pipe,
yet in long runs it amounts to sufficient to bring about a
rupture somewhere, unless provision is made for the movement
to take place freely and without strain.

Taking the extreme temperature of water from 32 to
212 (for the heat of the pipes is, of course, governed by the
temperature of the water), we get a difference in bulk (or, in
this instance, we may say length, as the increase in diameter
is not appreciable in this work) of I in 900, or, in other
words, a 100 foot length of cold pipe would, upon being heated
to 212, be increased in length by if inch not a great
increase certainly, but sufficient to break some joints if no
provision was made. In a long length of pipe it is not
sufficient that the extremity farthest from the boiler be clear

58 Warming Buildings by Hot Water.

to allow of this further projection, as the weight or pressure
exerted by the pipes upon their supports brings sufficient
friction into play to prevent their movement until a con-
siderable force is exerted, which in the meantime breaks the
joints or does some other damage. It is therefore necessary
(with long lengths) to rest the pipes upon rollers placed upon
the brick supports. These may be short lengths of round
rod iron or tube, or to secure neatness and
Fig. 35- stability an iron support with rollers can be

obtained, as Fig. 35. This ensures free move-
ment in expansion and contraction ; but this
is not sufficient by itself, as in the first place
the top (flow) and the bottom (return) pipes
of a main or a branch service expand to
different extents, as they are never at the
same temperature, and it will be seen that
very awkward results would ensue if this was not provided
for. Then again, from a long main service there may proceed
three "or more branch services, and it would not do for these
services (which are most probably carried off at right angles
to the main) to be carried to and fro as the main pipe ex-
tended or contracted itself, this being likely to do a deal of
mischief if the branches pass through a wall or were rigidly
fixed in some such way.

It therefore resolves itself into a necessity for provision to
be made not only for the pipes to have freedom to move
without binding on their supports, but this movement must
be made local, so to speak, to various points in the apparatus
by using expansive joints, which, as their name implies, admit
of a slight movement confined to the joint itself; or with
some of these joints we may consider they permit of a
sort of telescopic movement, so as to prevent the extension
continuing beyond the joint. More, however, will require to
be said about these presently.

It sometimes happens that in residence work the pipes
have been secured rigidly to their supports, or to the wall by
means of wedges or some such arrangement, or it has occa-

Expansion of Pipes.

sionally been known for the further extremity of a service to
terminate butt against a wall or partition ; in either of these
cases very unhappy results must be, and always are, ex-
perienced. In the latter instance the writer once saw a new
greenhouse wall pushed right out by the expansive force.

60 Warming Buildings by Hot Water.

CHAPTER IV.

IRREGULAR FORMS OF APPARATUS.

Dipping pipes below doorways and other obstacles Its effect upon the
motive power and general efficiency Velocity and its effect Practical
v. theoretical results Retrograde motion Calculations as to " dip-
ping " pipes Other phenomena Theory as to results obtained im-
mediately the heat is first applied to the boiler.

IT has already been explained that it is no uncommon thing
to have an apparatus which, from the highest point in the
flow pipe to the point where the return enters the boiler,
measures, perhaps, only 4 feet vertical, so that the circulation
of a large body of water depends solely upon a difference in
the weight of two short columns amounting to but I oz.,
without deducting any allowance whatever for friction or any
other trifling obstruction that may present itself. In all
horticultural works where but a small rise and fall in the
pipes is practicable, an obstacle must never be more than a
trifle, or the results will be partially or wholly bad.

Now it not uncommonly happens that with a view to
convenience, or from necessity, a pipe, the return pipe prob-
ably, requires to be carried down below its normal course,
usually when it has to pass a doorway, which it cannot do
without being carried down to a level with or below the floor
line as Fig. 36, and an instance might arise where a pipe has
to be taken down below the level of the boiler itself. This in
glass-house work is possible ; but it is not at the advantage an
apparatus is that is carried up two or three floors of a build-
ing, with, as a matter of course, a vastly increased motive
power.

The motive power of an apparatus can be increased by
increasing the vertical length of the flow and return pipes

Irregular Forms of Apparatus.

7 fx^v^^^^^^^

(with some limit), and also by increasing the length of hori-
zontal pipe, so that the water may lose more heat and create a
greater difference in temperature (and weight) between the
water leaving and entering the boiler. This also must have
some limit. In horticultural
work it has been pointed
out that the former of these
two methods can never be
resorted to with a view
to increase the motive
power, as every inch of
vertical pipe that can pos-
sibly be fitted is usually
required to work an appa-
ratus of an ordinary cha-
racter in the usual way. For we have to remember that the
house is usually placed upon the level of the ground (many
gardeners prefer having the floor of the house below the ground
level), the pipes cannot be put much above the floor level, and
the boiler cannot be fitted far below, as a very deep boiler pit
is objectionable and quite impracticable in many instances,
where water is obtained 2 or 3 feet below the surface of the
ground ; so that we may consider that an average height from
the return pipe at boiler to the highest point of the flow pipe
is about 5 feet, representing say 4 oz. as the motive power
certainly a very weak power to permit of our carrying pipes
in a way, or doing anything, contrary to what favours the
circulation.

The object in thus dwelling upon the insufficiency of the
motive power that is obtained in this particular branch of hot-
water works is to make it clear that precautions should always
be taken to avoid peculiarities in the construction of the appa-
ratus, particularly that of carrying pipes in a direction opposite
to what is favourable to its success, viz. a continually ascend-
ing flow pipe, and a continually descending return pipe.
For the disadvantages of a low motive power are in reality
two-fold, namely, the want of the power itself to increase

62 Warming Buildings by Hot Water.

the circulation and the loss in velocity of circulation, which is
clearly a drawback when obstacles have to be overcome, for
it takes much less to further retard or overcome the motion
of a sluggishly moving body (whether solid or liquid) than it
does to interfere with anything travelling rapidly, that is to
say, with a moderate impetus.

Before proceeding to discuss the possibility of " dipping "
pipes in their course, it is desirable perhaps to just explain
the question of velocity of circulation, as tending to make
matters still more easily understood, although really no
reliance can be placed on the results arrived at, as though
strictly correct in theory, they are so modified and varied in
practice, particularly by friction,* quantity and size of pipe,
&c., &c.

Hood grasped the subject of velocity very strongly, as
is evident by his treatment of it, as follows : " The velocity
with which the water circulates in this kind of apparatus

can be calculated theoretically when certain data

are agreed upon or are ascertained to exist This

* The writer is always in doubt as to whether the term " friction " is
correctly applied here. When we speak of this phenomenon we suppose that
it exists between two substances more or less rough (for the finest polished
surface shows a roughness under a powerful microscopic glass), this rough-
ness offering a resistance which prevents one of the bodies readily slipping
from the other when their surfaces are tilted more or less out of level. But
there are no substances so rough on the surface that they do not readily part
company if they are forcibly moved or tilted right over. This is not the
case with water, for if we take a finely polished surface and pour water on
it, it runs off as fast as poured on, with the exception of some of the liquid
that lies close to the surface referred to, and this, however it may be tilted,
still adheres, even if the object is turned upside down. Consequently there
must be an attractive or adhesive force the former, most likely, as we
cannot suppose it is a single layer of water particles that remains fastened,
so to speak, on the surface, but very many layers as the particles of water
are so exceedingly minute. This property is manifested almost the same
whether the surface be very rough or very smooth. It is therefore just
possible that the particles of water next the inner surface of the pipe are
quite still, although the particles of water next them may be in motion,
in the same way that in watching the circulatory movement of water
heated in a glass jar, we find the top surface or " skin " of the water is
perfectly still, as already explained.

Irregular Forms of Apparatus. 63

velocity is easily calculated ; a gravitating body falls 1 6 feet
in the first second of time of the descent, 64 feet in two
seconds, and so on, the velocity increasing as the square <3f

the time To estimate the velocity of motion of the

water in a hot- water apparatus, the same rule will apply. If
the average temperature be 170, the difference between the
temperature of the ascending and the descending columns 8,
and the height 10 feet, when similar weights of water are
placed in the two columns of an inverted siphon, the hottest
will stand '331 of an inch higher than the other, and this will
give a velocity equal to 79*2 feet per minute. If the height
be 5 feet, the difference in temperature remaining as before,
the velocity will be only 55*2 feet per minute, but if the differ-
ence in temperature in this last example had been double the
amount stated that is, had the difference of temperature been
1 6, and the vertical height of the columns 5 feet, then the
velocity of motion would have been 79 2 feet per minute, the
same as in the first example, where the vertical height was
10 feet, and the difference in temperature 8. This therefore
proves, in corroboration of what has been already stated, that
reducing the temperature of the water (that returns into the
boiler), either by using smaller pipes (which part with the
heat faster), or by increasing the length through which it
flows (so that there may be more heat radiated), has the same
effect on the circulation as increasing the vertical height?
leaving out the question of friction.

" The velocity for 3 feet of vertical height by the same rule
will be 43*2 feet per minute, for 2 feet of vertical height
36 feet per minute, and for 18 inches of vertical height it will
be 30*7 feet per minute, if the difference between the two
columns be in each case 8 the same as in the former
examples. It must be here observed, however, that, although
it appears by these calculations that increasing the vertical
height of the pipe fourfold will produce a double velocity of
circulation, as the water will then pass through the pipe in
half the time, the difference between the temperature of the
flow-pipe and of the return-pipe will be* lessened, so that the

64 Warming Buildings by Hot Water.

quadruple increase of height will only produce a rate of circu-
lation about one and a half times the original velocity."

As Hood remarks, such is the result in theory (as
regards the sums and figures stated). In practice we shall
never meet with an instance agreeing with these results, even
in an apparatus small in size and constructed upon the most
favourable principles. To get at the true velocity a large
amount must be deducted from these theoretical figures, as the
data given are arrived at upon the calculation that the sub-
stance is falling through air. Now air offers no resistance
comparable to water passing through pipes, particularly
those that are horizontal, the water in which is helpless
to assist in its own movement ; then every angle offers
additional resistance, not merely a resistance of friction, but
a tendency to obstruct the whole mass bodily. With an
ascending or descending pipe we more nearly approach the
theoretical velocity, but in these pipes we only get a true
velocity near the centre, the particles nearest the surface being
very sluggish in movement.

Hood explains that the motions in a vertical flow pipe
and a vertical return pipe differ in character by reason of the
outer particles not clinging to the pipe surface in the latter
pipe as they do in the former, but that the water in the
return pipe moves bodily, so to speak, instead of the centre
particles moving faster than the particles near the surface, as
they do in the flow pipe, as just explained. The writer has, it
must be feared, to contradict this, as in numberless experi-
ments with glass pipes this phenomenon has never been
detected. It is obvious from Hood's explanation that the
deduction has been arrived at by considering the water in
the return pipe to be cold, which of course only happens
wnen the fire is first started, as this is afterwards rarely
allowed to go out (unless it is a small amateur apparatus).

Now in dealing with an apparatus in which we wish to dip
one or both pipes below their normal course, that is, to make
the pipe descend to pass some obstacle and then rise up to
its original level, we have to remember first, that we introduce

Irregular Forms of Apparatus. 65

an obstacle to the natural course of the circulation, and,
secondly, that in horticultural work the circulation at its best
is hardly anything better than feeble. The cause of a dip
proving a check to the circulation is as follows :

We may suppose an apparatus constructed as at Fig. 37,
exceedingly simple, as it is merely a pipe proceeding all

Fig. 37-

round a greenhouse,* but in carrying the pipe along all four
sides of the house we encounter a doorway under which
the pipe must be carried at the floor-level as shown. Now
from the top of the boiler to the point E everything is
normal (as in fact it is to the point G) ; but in the vertical
pipe E to F we have a descending column of water lighter
than the ascending one in the pipe G to H, as according to
the principles laid down the water gets colder and heavier as it
gets nearer (in its return) to the boiler, due to loss of heat by
radiation.

The fact of the water in the pipe G, H being heavier than
that in the pipe E, F naturally tends towards a back or retro-
grade movement, as it is now clearly understood that it is the
fact of the water in one pipe being of greater weight than that
in the other (of the ordinary circulating services) that brings
about the movement which is termed the circulation, by the

* Let it be clearly understood that this is not the usual way of arrang-
ing the pipe or pipes. They are usually carried up and down two or three
sides of the house so as to avoid the doorway, as will be explained later ;
the above arrangement is merely adopted for the purpose of illustrating
the " dipped " pipe.

66 Warming Buildings by Hot Water.

heavier forcing the lighter bulk before it, and not the heavier
giving way, retreating before the lighter, as we require it to do
in this instance.

In the simple dipping of a pipe under a doorway there is
no very marked difference in the temperature of the descend-
ing and ascending pipes referred to, as they are so near
together, although there is quite sufficient difference to bring
about a movement in the wrong direction if the general motive
power of the apparatus did not exist. If a distance of
say 20 or 30 feet separated the two points F and G, a greater
obstacle would present itself, as the greater the distance
between these two points the greater must be the difference in
the temperature, and consequently the weight of the water
in the two pipes indicated. It may be accepted as a rule that
the greater the space referred to, the greater the resistance
offered in the circulation.

Now the motive power of the apparatus must be sufficient
to overcome this inclination to return movement, and it must
be sufficient also to have a surplus of power to produce the
general circulation required. This residue of power should
be sufficient, as a feeble movement will not only fail in con-
veying heated water to the extremity of the apparatus by
reason of its slowness permitting the heat to radiate before it
can get to its destination, but it will readily fail if an obstacle
get in the pipe ; a leaf (so frequently found in the pipes) or a
collection of refuse would totally stop the circulation. This
requires consideration, as in most country places, pond, ditch,
or surface water is used to charge the apparatus.

To show a simple way of calculating if the dip in the last
illustration is permissible, we can take another figure, Fig. 38,
and by spacing it out in imaginary degrees of temperature as
shown, tolerably correct results can be arrived at by comparing
the mean temperature in the ascending and descending
volumes of water. From A to B we have 179 mean, and
from J to K we have 141 mean, a difference of 38, and to
this we can add, say, one degree for the portion of vertical
return pipe at C, D, making 39 to produce the circulation if

Irregular Forms of Apparatus. 67

the dip was absent. If we take the mean temperatures of the
two vertical columns of this dip we find there is a difference of
7, this being 7 of resistance to the circulation, and which has
to be deducted from the 38 last mentioned. This, it will be
seen, however, leaves ample margin of motive power in this

Fig. 38-

i :\

5)*

_J.

1*2 1*3 .
140 '45'

[[ 153 IS4 155 156 157 158

ISO

14.6 14-7 140 149

case ; but, as already pointed out, if we increase the space
between G and F, or increase the depth of the dip, further
resistance is offered.* In Figs. 37 and 38 just explained, the
dips are shown in that portion of the pipe that is returning to
the boiler, whereas in Fig. 37 the flow pipe might have been
carried towards the doorway, where the dip has to be, first ; in
this case no more nor less resistance would have been offered
by the dip itself, supposing its dimensions to be the same in
each case, but when first starting the circulation the obstacle
(for the dip is an obstacle) would be encountered before the
circulation gained the impetus it would do if the dip was
situated as Fig. 38. We must give every consideration to
what happens when the circulation is first started, as any ill
effect that is to be experienced will give the greatest trouble
at this time.

In Hood's description of this he shows the dip in the
flow pipe as Fig. 39, his explaination dealing only with the
resistance offered by the dip irrespective of its situation as
follows :

" In an apparatus constructed thus, the motion through the
boiler and pipe A, B, and through the descending pipe C, D,
takes place according to the principles described. But it is

* It must be explained that in these calculations again, the results are
but theoretical, as the temperature of the air, the size of the pipes, and the
position of pipes, all tend to vary the general effect.

F 2

Warming Buildings by Hot Water.

evident that, on motion commencing in the return pipe y y z, in
consequence of the greater pressure of C, D than of A, B, the
water from A will be forced towards , at the same time that

the water in , /, g, h flows to-
wards C. But when a very
small quantity of hot water has
passed from the pipe and
boiler A, B, into the pipe *?,/,
the column of water g, h will be
heavier than the column e, f,
and therefore there will be
a tendency for motion to take
place along the upper pipe

towards the boiler instead of from it. This force, whatever
be its amount, must be in opposition to that which occurs in
the lower or return pipe, in consequence of the pressure of
C, D being greater than A, B ; and unless, therefore, the force
of motion in the descending pipe C, D be sufficient to over-
come this tendency to a retrograde motion, and leave a residual
force sufficient to produce direct motion, no circulation of the
water can take place." Now if we can dispose of the ascend-
ing pipe G, H (Fig. 37), and continue the return pipe straight
from G to K, the circulation becomes normal, which is of
course the best course to aim at if possible, but this is governed
chiefly by the distance from G to K, as it is not desirable to
carry this pipe below the floor-level and probably lose its heat,
unless it is a matter of a few feet only.

In all the illustrations referred to, the dip has not been
shown as extending below the point where the return pipe
enters the boiler, in fact, its depth would not need to exceed
24 inches at the utmost ; but, paradoxical as it may seem, it is
quite possible to extend the dip below the bottom of the boiler
without creating any greater obstacle or resistance to the
circulation than with the dips already explained.

Supposing a deep dip to be required at some point near
the boiler (in which case the pipe would not be required to
ascend to its original level again), the pipe could be arranged

Irregular Forms of Apparatus.

as Fig. 40, in which, by spacing out in imaginary degrees of
temperature, we get a mean of 179 in the ascending pipes
A, B, and a mean of 149 in the descending pipe E to *,
the difference being 30 in favour of the circulation without

Fig. 40.

74 173 172 171 170 169

iCa 167 tS 165 164 163 C

,162

50 151 152 153 154 155 156 157 ISfl I5S 160
143

143 144 14-5

the dip ; the resistance offered by the dip is 6, leaving a suffi-
cient margin for effective work, to which may be added the
effect of the small piece of descending pipe C to D.

In this instance it will be seen that the apparatus is
normal from the top of the boiler at A to the point in the
descending pipe marked,* which is opposite the point where
the return enters the boiler. It is almost the same (so far as
the resistance offered by the dip is concerned) as placing the

Fig. 41.

dip as Fig. 41, therefore if this dip is of the same dimensions
as the one described in Figs. 37 and 38 it will only offer the
resistance to the circulation that these latter would do, even
though in one case the dip extends below the bottom of the
boiler and in the other the dip does not reach this point. In
this case, as in the others, the resistance is increased by in-
creasing the space between F and G, and also, of course, by
increasing the depth of the dip.

70 Warming Buildings by Hot Water.

In describing the results obtained from an ill-formed
apparatus, Hood points out that occasionally an apparatus
can be met with which, although apparently constructed on
the worst principles, has, in consequence of various circum-
stances, been favourable in results ; and he goes on to describe

an apparatus constructed as
Fig. 42, where the pipes were
not more than 3 inches apart,
"yet the water circulated
with freedom, but in this case
not only was the pipe of con-
siderable length, and without any angles or turns, but the size
of the pipe was only 2 inches diameter, so that the pipes
cooled twice as fast as they would have done had pipes of
4 inches diameter been used " (see pp. 243, 298, &c.).

It can hardly be supposed (although the intention seems
very clear) that Hood intended this last-described apparatus
to be an instance of "construction on the very worst
principles/' as there are hundreds if not thousands of small
apparatuses carried out in precisely this manner. Pro-
viding all other points in the apparatus are correct, the
distance between the two pipes is sufficient to ensure success,
if the apparatus is small in size. There is a very common
practice (which, however, cannot be recommended for reasons
to be presently stated) of heating a small greenhouse or
conservatory from a kitchen range boiler. If the floor of
the greenhouse is on a level with the kitchen floor, or a little
below it, as is often the case, the pipes will most usually be
found taken from the side of the boiler, which will not always
permit of their being more than 3 inches apart, yet so far
as the circulation is concerned all goes well, so much so that
a complaint is rarely heard of its working badly.

If an apparatus was constructed as Fig. 43, with the pipes
as exactly level as possible to get them, a free circulation
would be found to set up in the pipes and without any hesi-
tation at the start, although it cannot be relied upon to
circulate in the same direction every time it is started afresh,

Irregular Forms of Apparatus. 71

as, in a series of experiments made with this apparatus, it was
found sometimes that what hitherto answered as the flow pipe
acted as a return, and vice versa, although there seemed to be
a preference for one pipe to act as an established flow pipe
and the other as a return.

If we carefully investigate the question of how the circu-
lation first starts or sets up, we shall see that it is quite

Fig. 43-

natural for it to act and traverse the pipes (circulate) that
are connected on a level with each other as just described.
Whether inquiring upon a theoretical basis or from results
obtained from practical experiments, we shall find that in-
stead of the water failing to circulate (when the apparatus
is constructed contrary to accepted notions) the difficulty
will be to get the water to remain still an apparatus has to
be erected in an extraordinary manner to wholly prevent
the water moving in the pipes.

Returning to the apparatus with the pipes starting level
(Fig. 43), in accounting for the results we must consider what
happens when heat is first applied, the water in all parts of
the apparatus being stationary up to this moment. Move-
ment may be considered to first take place in the water
nearest to the source of heat, which we will suppose is at the
bottom. Almost at the very instant the particles are noticed
to move there they will be found moving in the other parts
of the boiler also, for the movement everywhere is almost
simultaneous, as it can be so readily seen that the movement
of water at the bottom of the boiler is due to and dependent
upon the pressure and consequent movement of the water at
the top.

Now the instant the water in the boiler becomes warmed

Warming Buildings by Hot Water.

and rarefied and is in movement, we should have the pheno-
menon of hot water being in the boiler and cold water in the
pipes extending from the top of the boiler. In other words,
we may rightly consider the pipes as an extension of the
boiler itself, in which case we should have hot water in the
general body of the boiler, while a portion of the upper part
is tenanted by cold water, and this, it is needless to add, is
against all principles, and cannot exist unless the portion of
cold water referred to was confined in some way, and even
then it would set up a circulation of its own, if the hot water
imparted heat to it. We thus see that the cold and heavier
water cannot remain in these pipes at or near the top of the
boiler if they have free communication with the heated water
which is practically beneath them, but it is equally obvious
that the cold water cannot come down both pipes at the
same time : one must act as a flow pipe and the other as a
return, and this they readily do. The only inference to be
arrived at for their so acting is that they may not be perfectly
level, or some inequality or trifling obstruction
in one pipe permits the other to take the lead.

We have practically the same result when
we connect vertical pipes both on top of a boiler
(without continuing one of them down inside),
as Fig. 44, only that the explanation just given
bears even a stronger application in this case,
as the water within the pipes is truly on top of
the water in the boiler, and it certainly will not
remain there when the latter becomes heated ever
so little, and a circulation will be found to set up
directly heat is applied to the boiler. It is a
common impression, particularly amongst work-
men, that this last arrangement described would
fail to act by the water remaining stationary in
the pipes, although the water would become of a high tem-
perature in the boiler, but this is incorrect, for the water will
never fail to circulate up one pipe or the other. It is most
peculiar to note that when the pipes start level, no reliance

Fig. 44-

Irregular Forms of Apparatus. 73

can be placed as to which pipe will act as a flow and which
as the return. Sometimes the water will proceed up one pipe
when the apparatus is first started, and when the circulation
is once established it will continue acting in the same way.
If it is allowed to cool down again and the water to become
stationary, then it is just possible the water will flow up the
other pipe when started again. This will be more fully in-
vestigated in a later chapter, when treating of branch services.

It must not be supposed for one moment that in dealing
with the circulation that takes place when pipes are started
from level points, it is intended to recommend this method.
The question has been dealt with to dispose of or put upon a
more sound basis one of the little problems that are always
presenting themselves in this work. The customary plan of
having the flow pipe from 9 to 30 inches above the return
pipe, that is, the flow pipe at the extreme highest point
in the boiler and the return at as low a point as possible, is
decidedly the best arrangement. It is reliable, for the water
will always circulate one way, and it in every way aids the
natural effect.

Hood has set it down that 12 inches should be the
recognised minimum distance between the two pipes : this
is a safe and practical suggestion. It is somewhat unusual
if this space cannot be had, as boilers made for heating
purposes are seldom less than, say, 15 inches high. The
illustrations, Figs. 23, &c., show the correct points for the
two pipes, but of course the return can come in at either or
both sides, and it is not absolutely necessary by any means
for the flow or return to be situated centrally from front to
back, as will be seen in the various illustrations of boilers on
later pages.

74 Warming Buildings by Hot Water.

CHAPTER V.

IRREGULAR FORMS OF APPARATUS continued.

A WELL-KNOWN and talented author upon " Heat " * clearly
explains (theoretically) to what extent a pipe may be dipped,
as shown in Figs. 45 and 46. In the first figure we have an
apparatus which would undoubtedly extend up one or two
floors of a building (thus differing from the horticultural form
of apparatus, which has been almost exclusively treated up to
this point), its construction being normal, and showing a
mean temperature of 160 in the ascending column and 117
in the descending column, a difference of 43 degrees to fur-
nish the motive power, which, it is needless to add, would
create a very rapid circulation in an apparatus wholly of
vertical pipe. In Fig. 46 the mean temperature in the
ascending column is about 135, and in the descending column
135 also, so that theoretically there should be no circulation
at all ; or, if we vary it a little by placing the boiler a little
lower than shown in Fig. 46, as at Fig. 47 for instance, the
mean temperatures in ascending and descending columns
would be, say, 134 and 128 respectively, a difference of 6,
which would produce a less rapid circulation. But according
to the principles laid down this would be sufficient to do
moderately effective work in a vertical apparatus, and shows

* Box upon ' Heat ' ; London : E. and F. N. Spon.

Irregular Forms of Apparatus.

conclusively that the higher we carry the ascending column
the greater the motive power obtained, and consequently
permitting of the return pipe being carried to a greater
distance below the boiler than when the ascending column
is of limited height, as we get it in horticultural works.

Now, as before mentioned, this is strictly correct in
theory, but if any one erects a model apparatus as at Fig. 48,
in which the pipe descends below the boiler, say three times as

Fig. 45-

140

Fig. 46.

Fig. 48.

130

170-

105-

135

much as it rises above it, upon heat being applied to the boiler a
circulation will almost immediately set in that is to say, as
soon after the application of heat as in an apparatus of
normal construction, and the circulation will be in the correct
direction, viz. ascending up the short pipe at the top of the
boiler and returning by the pipe that enters the boiler near
the bottom.

Although we may only make this experiment in a small
model apparatus, yet the results in this case may be quite

76 Warming Buildings by Hot Water.

relied upon as being natural, although a little thought will
show that it is opposed to all accepted principles.*

It is easy to account for the circulation or movement that
first occurs in this case, as we may consider the whole of
the apparatus above the two points marked * to be of a
normal character, and the part below these points simply
consists of an inverted siphon with an equal weight of water
(while cold) in each leg, so that when heat is applied to the
boiler we must, as a matter of course, quickly have the water
in the column A, B lighter than in the column C, D, which
will be sufficient to produce a movement in the direction of
B to C, for while the water in the pipes below the points *
remains cold (that is to say, not yet affected by the heat) it
will have no effect whatever upon the circulation, no more
than to move in whichever direction the difference in pressure
in the pipes above may cause it. This may account for a circu-
lation setting in when the heat is first applied, and up to the
time that the heated water has travelled round to D, but when
in the course of circulation the heated water reaches the point
E or F (but not yet past F) then we shall have the column B
to F heavier than C to E, yet the circulation continues (but
more sluggishly) in the direction in which it started, and does
not cease to do so so long as heat is applied to the boiler.

This experiment, although demonstrating a peculiarity in
hot-water circulation as regards the principles and theories we
recognise at present, is not valuable, as although the circula-
tion remains constant it is of so low a speed as to be useless
for large works. But supposing such an apparatus was
needed, then its efficiency could be rendered secure by apply-
ing heat to it at F, or at a low point in the pipe between
F and G not an additional boiler, but by passing a piece of
the pipe through a small fire (which, however, would require
to be kept alight all the time the apparatus was at work), or

* As this book goes to press there is an apparatus exhibited at the
Crystal Palace which has the flow pipe carried from the side of the boiler,
descending to heat some coils below it, and then returning into the bottom
of the boiler, no part of the pipe services being as high as the top of the
boiler.

Irregular Forms of Apparatus.

Fig. 49.

by applying a moderate sized " Bunsen " gas burner, which
would be, perhaps, easier of application and certainly very
regular in results. This, it must be quite understood, is sup-
posing that the boiler cannot anyhow be placed at the lowest
point, as it should be if possible.

Hood describes a method whereby the introduction of
some extra pipe or radiating surface, which he shows in the
form of a coil, is the medium by which he can carry the pipes
before the boiler to a greater extent than can be done if this
coil was absent, and without
impairing the circulation. His
description is as follows :

" In an arrangement of
pipes, such as Fig. 49, the
circulation will depend en-
tirely upon the quantity of
heat given off by the coil c,
for it is evident that when
the boiler B and pipe a are
heated, the direct motion will
arise in consequence of the
greater weight of the water
in the coil c and pipe d
above that which is in the

boiler and pipe B a. But as the water in the pipe e y below
the dotted line, will be lighter than that in the pipe /, the ten-
dency in that part of the apparatus will be towards a retro-
grade motion.

" The result of these two forces will be that if the water in
the whole length of pipe w x is heavier than that of the whole
length y z, in a sufficient degree to overcome the increased
friction, circulation of the water will take place, and the
velocity of motion will depend upon the amount of this
difference in weight."

Nothing could be more sound than the principle here laid
down viz. that by putting a coil at the point shown we are
able to dissipate more heat and make the water heavier by the
time it exerts its influence in the descending pipe, and by

Warming Buildings by Hot Water.

this means it is rendered of greater power in overcoming the
obstacle of the ascending pipe f, which is understood to be
full of the heaviest water. But we could obtain the same
result without the coil if we subject the pipe at the point w to
some cooling influence, such as passing it through a small
tank of cold water or exposing just this point to the outer air.
This brings most forcibly to notice that in the majority of
cases the mere fact of cooling the pipe here is, of all things,
what should be avoided, as we may suppose that the object in
carrying the pipe down below the boiler is for the purpose of
providing heat (by a coil or series of pipes) at some point
between x and z, in which case the object would be completely
frustrated by the cooling influence at w. Therefore, although
the principle is sound, it is not practicable, as a dip of such
depth would never be necessary unless for some useful heating
purpose, and then very little heat would be obtained.

Supposing such a dip was required, but not for any heating
purpose, then the coil would be permissible, but perhaps it

Fig. 50.

would be more useful to extend the pipe at the point w (as
Fig 50), and so make some good use of it instead of coiling it
up, as the result would be practically the same.

Hood also describes another method having the same
principle and effect and the same drawback as the last, but

Irregular Forms of Apparatus.

instead of using a coil as the medium for cooling the water
and rendering it heavier, he shows an apparatus, as Fig. 5 1, in
which the flow pipe is carried by the nearest and most direct
route to an open feed cistern or tank, and from there it is
carried to wherever the heat is needed. He indicates a
preference for this, owing to the absence of the friction which
a coil would entail, and which is somewhat considerable.

Fig- Si-

3 L

It will be plainly seen that if this cistern is going to be
used as a means of cooling the water somewhat, that its use
will be prejudicial to the object for which the apparatus is
intended, and on this account it could not be recommended ;
but if the cistern is kept with a cover upon it, and in a fairly
warm position, this method has some points in its favour,
and it is not at all uncommon to meet with an apparatus so
constructed and doing good service.

In the first place it is understood that the cistern acts as a
supply or filling cistern, and it possesses the advantages of
allowing the freest possible escape of air and also of steam
should the boiler become overheated. It prevents in a great
measure, and in some instances entirely, the passage of air
into the return pipe or pipes, and it will be readily seen that
air, however small the quantity, must take up some space, and
consequently will render the contents of the pipe or pipes

8o Warming Buildings by Hot Water.

lighter than if air was absent, so that the whole of the space
would be occupied by water. When this arrangement is
adopted it can be made to bring about a saving in stop valves
or cocks, as, supposing it can be conveniently carried out,
there is one flow pipe of a sufficient size from the boiler to the
tank, but from the tank there may proceed two or even three
or four return pipes to the boiler, the number being governed
by the different directions in which the pipe requires to be
taken ; then whenever one or more of these services require
to be stopped, it is only necessary to insert a wooden plug
into the pipe where it appears inside the tank, and this plug
will of course prevent all flow of water through the pipe in
question. One of the chief reasons, however, for the adoption
of a tank (into which the water is circulated) is, that by fixing
the tank in a high position, as near the roof of the glasshouse
as possible, we get a higher motive power, and by this means
we can with greater facility circulate below the level of the
boiler, as (see ante) it has already been explained that one of
the means of increasing the motive power is to increase the
vertical height, and the greater the vertical height the greater
the extent to which we can dip below the boiler.

An instance where this arrangement becomes desirable is
when we have two or more greenhouses to be heated from one
boiler, these houses being upon irregular ground, so that they
stand at different levels, and it is found impossible to have the
boiler at a lower level than shown. In this case it becomes
possible that one set of pipes has to be carried a little below
the boiler as Fig. 52, and in this case a tank becomes a
necessity, as we should get poor results by running a pipe
directly from the top of the boiler down to a point below its
level, then up again on its return.

The illustration shows the tank fixed, this tank, however,
being closed and having a steam or air pipe from it ; this
certainly does away with the convenience of plugging the
pipes, but it is the best arrangement to save the heat and
prevent a too lavish distribution of vapour.

It must not be overlooked that in all these unusual forms

Irregular Forms of Apparatus.

of apparatus air cocks or pipes play a more important part than
ever, and in practice it will be found that a good deal of

judgment is required to successfully rid the pipes of air in a
thorough manner, a very necessary requirement, as it will be

82 Warming Buildings by Hot Water.

understood that in departing from the normal arrangement we
must in a greater or less degree impair and lessen the motive
power, and but a trifling accumulation of air under these
circumstances may ruin the efficiency altogether.

In Fig. 36 an air vent would have to be placed at the
highest point of that portion of the pipe on the right-hand
side of the door, and also at the highest point of the pipe on
the left side, as a dip like this is a certain obstacle to the
passage of air either way, whether it be the flow pipe or the
return. It may be pointed out that in this arrangement the
depth of the dip can be reduced by using a special form of
pipe that is made to pass under doorways, this pipe having
a flat even top, so that it need not be covered with earth or
the paving material, but be fixed level with the floor line.

In Fig. 37 we may suppose the pipe ascends slightly all
the way from A to C, this latter letter being at the highest
point, where an air vent would be required. From this point C
the pipe decends to F, and no further outlet would be required
thus far, but at H (which we may suppose is a trifle higher
than J) another vent would be needed, as any air collected in
this short piece of horizontal pipe would not be able to escape
either way, it descending at both ends, neither could this pipe
(J to H) properly fill when first charging, unless an air vent
be there.

In Fig. 38 an air vent would be needed at C, and one also
at H (supposing H to be a trifle higher than J) in exactly the
same way as the last described.

In Fig. 39 we have practically the same apparatus again,
although the dip is situated differently ; at e an air vent would
be needed, as we may suppose this point is a trifle higher than
A, and again at C would provision have to be made for air
exit ; at no other point in the apparatus would it be needed,
provided the apparatus is erected in the usual way, which
would make C the highest point

In Fig. 40, again, the point C should have its air vent, and
this in a small apparatus would be sufficient, but if where the
return enters the boiler there is ever so short a length of pipe,

Irregular Forms of Apparatus. 83

it would be a most desirable plan to put an air vent in it at its
highest point of course. In a short length of pipe it might be
fixed in a manner that would be considered perfectly hori-
zontal, and a difficulty would be experienced in deciding
where to put the air vent, but this can be settled by using a
spirit-level. It will be noticed that nothing could give us
better results, as the chief feature in this article is a pipe
having water with a globule of air imprisoned within it, the
direction which the air takes in the spirit-level being exactly
the direction the air will take in the hot-water pipe,
supposing the level to be resting evenly upon the pipe in
question.

In Fig. 41, again, C is the necessary point for an air vent,
and also H if we suppose H to be a trifle higher than the
point where the pipe enters the boiler. The two pieces of
horizontal pipe on the opposite side of the dip to H do .not
require any provision for air exit, as these should both ascend
towards the point C, i. e. descend toward the boiler.

In Figs. 42 and 43 an air vent would be needed at the
termination of the pipes furthest from the boiler (as shown in
Fig. 43), but if an apparatus was constructed in this manner
the boiler itself would also require an air vent of some sort at
the top, as will be seen.

In Fig. 5 1 we touch upon debatable ground when suggest-
ing a position for the air vents. One of course would need to
be at the tank, unless it has an open top or loose lid, but in
the circulating pipe it depends entirely upon how this is run,
as there are in this system as many advocates for making the
upper pipe descend towards the end, the under pipe being
carried horizontally as Fig. 53, as there are advocates for making
these two pipes ascend towards the end in the usual way as
Fig. 54. In the former case an air vent should be provided
where shown, to prevent a possible air-lock when re-charging,
and to aid when first charging ; and in the latter case the air
vent would require to be placed at the accustomed extremity
as shown.

There is every argument in favour of carrying the pipes,

G 2

84 Warming Buildings by Hot Water.

under this particular tank system, in the manner shown at
Fig- 53, thus treating the pipe from the tank to the boiler
wholly as a " return " ; it allows of the freest possible escape
of air, and brings about more natural results.

Fig. 53-

Fig- 54-

In Fig. 52 is introduced two most distinct systems, but
which will work in complete harmony (with a little care), and
the results obtained by both arrangements should be satis-
factory in every way. The whole of the apparatus on the right-
hand side of the point marked A is of the most simple descrip-
tion, and an air vent at the extremity as shown will suffice
for this portion. An air vent is needed in the tank unless it
has an open top or loose cover. This is regulated by the use
to which the house is put ; as an instance, we may say that
an open top would not do in a grape house, where an excess of
moisture is usually objectionable. In the pipes on the left side
of A, an air pipe can be fixed as shown if these pipes rise
towards that extremity ; but as just described, it is better to
arrange them as Fig. 53, in which case an air pipe should

Irregular Forms of Apparatus. 85

be fixed at B, which however might not be so much needed at
first charging, but we have in this case to bear in mind that
unless special provision is made, the lower pipe on this side
will not be emptied when the apparatus is discharged for any
purpose, and this would cause a trap to be formed for air
when recharging. The tank in this system should be from 10
to 25 gallons capacity, according to the magnitude of the job,
but the water supply must not be arranged for the tank to fill
more than about a third or half full, as already explained under
water supply. The upper termination of the flow pipe need
not stand up more than 3 inches inside the tank, and the
pipes A to C, and E to G need not be more than 2 inches,
unless they are all within the house and diffuse a useful
amount of heat as the other pipes do. If any part of the
pipes just named are carried out in cold situations (under-
ground or outside the house) it is very necessary indeed to
cover them in some way with a poor conducting material,
to prevent loss of heat, as will be explained fully. It would
be very necessary in this apparatus to provide throttle valves
to each set of pipes, as it may be taken for granted that the
portion of the apparatus on the right of A will have the freest
circulation, and will take the ."lead" as it is termed, and it
will be found that if the circulation starts in one direction
more strongly than another it will continue so, and the part of
the apparatus that is working the least effectively will fail to
pick up and recover itself, in fact it may seem to get worse.
This, however, is exceedingly easy of remedy by the use of
valves, the gardener regulating them as necessary or accora-
ing to his desire. Even in an apparatus constructed upon
simple principles, if it has two or three distinct branches,
the gardener usually finds some regulation necessary, and,
strange to say, the regulation varies considerably in the
same apparatus, one branch working freely at one time and
sluggishly at another.

The water supply (still referring to Fig. 52) is arranged for
by the erection of a small filling cistern at the side, this, how-
ever, is not so necessary if the tank can be permitted to have

86 Warming Buildings by Hot Water.

a loose cover or open top. The filling is done by hand
from a can, or by a ball valve if a regular service of water is
accessible. In rilling by hand we have an objection in the
fact of the tank being situated up out of reach, and it is not
easy to tell when the supply wants replenishing unless an
indicator is fitted. The usual indicator is a float inside the
tank, a pulley on the top of the tank, at the edge, and a piece
of wood to drop down outside ; this piece of wood being
connected with the float by a light chain
or cord which passes over the pulley as

Fig- 55-

It will be noticed that there is a deep
dip in the pipe that connects the small
cistern with the tank, the object of this
dip being to prevent the contents of the
small cistern becoming hot, which would
be of no advantage whatever. It has been

explained that water (when warmed) will circulate with con-
siderable freedom in a single pipe from a boiler, and in the in-
stance just referred to, we may consider the tank as acting the
part of a boiler, and a circulation would set in, we may say
immediately, between the tank and the small cistern if the con-
necting pipe was straight, i. e. not dipped. The circulation
would certainly be sluggish, but nevertheless sufficient to make
the water in the small cistern hot, which would be an objection
that the small cistern is provided expressly to obviate. The
feeble circulation that sets up in a single horizonal pipe is
immediately checked when the pipe commences to descend.
This dip should be about 10 inches deep ; a small plug could
be fitted in the lowest point of this " siphon " (as it is wrongly
(called if any liability of stoppage by dirt, &c., exists.

CHAPTER VI.

CAUSES AFFECTING CIRCULATION OF WATER IN
APPARATUS.

Friction Table of relative degrees of friction in different sized pipes
Different purposes for different sized pipes Limit to circulation As to
limiting the lengthiof services Obstructions and faults Erratic results
and their causes The effect of air in circulating pipes Reversed cir-
culations As to whether the flow or the return services should contain
the greatest amount of water.

THE subject of friction has an important sound, and in theory
it ranks as a moderately important subject, but it is doubtful
whether the question has more than the scantiest attention
from the hot-water engineer. No one can aim at more than
constructing the apparatus on as simple a plan as possible, so
that the least number of bends, &c., are used. Any other
responsibility is met by using a boiler that the makers
guarantee to be powerful enough for a certain length of a
certain sized pipe.*

The boiler-maker, in arriving at the working value of his
boilers, has to consider the question of friction to some ex-
tent, or, in any case, allowance has to be made for it, as in
estimating the result that a certain area of heating surface
will give, this is always calculated first upon the basis that no
friction or resistance of a like nature exists.

Hood gives a table of the relative amounts of friction
or resistance by friction that arises in pipes of various sizes.
This table is sufficiently accurate for all practical purposes,
although not strictly correct as to fractions of quantities

* See boilers and the rule as to deductions to be made in arriving at
the practical value of the boiler as against the theoretical figures given by
most boiler-makers.

88 Warming Buildings by Hot Water.

which, however, are really not needed for this purpose. The
results are arrived at by emptying the contents of a given
sized vessel, from a given height, through various sized pipes.
It is found that if water passes out through a i-inch pipe in
say ten minutes, it takes less than half this time for the water
to pass out through a pipe of exactly double the area, and as
the pipes get larger the time becomes less than what is pro-
portionate to the size.

Diameter of pipes \ I 2 3 4 inches.

Friction 8 4 2 1*3 i

From this we see that the smaller the pipe the greater the
resistance opposed to the motive power, and although it has
been shown that the motive power (other circumstances being
favourable) is increased by using small pipes which lose their
heat faster and so create a greater difference of temperature
between the outflow and inflow at the boiler, yet by aiding
the circulation in this way we introduce another objectionable
feature, which may be said to about equalise and make the
effect only the same as a larger pipe. On this account larger
pipes have come to be regularly used and the more readily
that their cost is less in proportion.

In horticultural works it may be said that 4-inch pipe is
always used, the only exceptions being in cases where the
apparatus is very small, or where the gardener has some
special idea of his own, for, as already stated, the gardener
usually has considerable authority in this matter.

For churches, chapels, and halls, or any places where the
apparatus is not working continuously, smaller pipes are often
used, as it is desired to heat the building up as quickly as
possible after the fire is lighted. One 4-inch pipe with its
circumference of 12 inches holds as much water as about four
2-inch pipes with an aggregate circumference of 24 inches :
it will be seen from this that the advantage is with the latter,
which has so much more radiating surface for distributing
heat quickly. On the other hand, of course, it cools more
quickly when the fire is slackened ; however, that is not

Causes Affecting Circulation. 89

objectionable in church work, though it would be in horticul-
tural buildings.*

The fact that from a fluctuating fire large pipes distribute
heat more regularly than small ones is one of the chief
features in their favour, but at the same time nothing is gained
by having larger pipes than 4-inch.

If it were not for friction it is reasonable to suppose that
we might continue the circulating pipes for an enormous dis-
tance a mile for instance ; but under present circumstances
this would be no advantage. The longest distance in a
horizontal direction that the writer ever saw an apparatus
carried was 250 feet, extending from the extreme east to the
west wing of a nobleman's residence. This, which was upon
the high pressure system, worked excellently.

In the same way we might consider that the increase of
vertical height in an apparatus would increase the motive
power proportionately to an indefinite extent, but in this case
the friction would eventually reduce it to a mean rate. But
fortunately this need give us no anxiety for the present, as
the highest buildings we have would not be high enough to
bring any objectionable features into play.

If an extensive apparatus (extensive horizontally) had to
be erected, it would be better to arrange for two or more
distinct services to be carried in different directions in pre-
ference to one continuous apparatus extended hither and
thither all around the building. This would be done by
placing the boiler somewhat centrally to the work to be done,
or in some instances by taking a main flow and return to
a central point and thence branching off in different direc-
tions. This will not reduce the friction in aggregate, as we
may suppose that about an equal quantity of pipe is used in
each case, but in using the long single service the friction
reduces the flow of water to the extent that by the time it is
nearing its return to the boiler it will have lost all its heat and

* The writer knew a church where it was the practice for years to light
the fire every Friday evening to heat up the place to a satisfactory point
for Sunday.

90 Warming Buildings by Hot Water.

be worthless for any purpose near this point. In other words,
two or more short services which do not permit of the loss of
a great amount of their heat by the time they return into the
boiler are preferable to one unusually long service in which a
greater portion of the return pipe contains water cooled down
to a somewhat ineffective temperature by reason of the
comparatively long time that has elapsed since it left the
boiler.

It will be understood that the length of horizontal pipe
could be effectively increased by increasing the height of the
vertical portion, as by the latter means we increase both the
motive power and velocity. By thus increasing the speed of
circulation we proportionately overcome the trouble referred
to, as the quicker the water is in getting back into the boiler
the less heat it will lose in its passage. Of course there will
not be a less amount of heat radiated in the aggregate, that
is. in a given time. The whole of the return pipe will be
usefully distributing heat, and the heat will be more equally
distributed everywhere. The plan of increasing the vertical
height cannot, however, well be adopted in horticultural
works, as will be understood.

In suggesting that preference should be given to two or
more services in place of one very long one, it must not be
thought that an eighty or hundred foot run is too long by
any means. Where there are three or four glasshouses all
in a line it is quite the usual and proper thing to heat them
from a straight line of main pipes coming from a boiler
situated at one end. It is intended to suggest that when
there are three or four houses not in proximity or in line, but
scattered about somewhat, it is best to take a separate service
to each rather than continue the one main service from
the boiler around the whole group. This, however, is another
question that the gardener usually settles, very many of them
preferring to have more than one boiler (of a proportionately
smaller size), even though the houses are near enough to be
all heated from one fire.

It may be here mentioned that never in any two cases

Causes Affecting Circulation. 9 1

will opinions as to the planning of a work be found to agree,
but the principle involved is of course the same always.

As already explained several times, the power which
brings about the circulation in horticultural works of an
ordinary character is, at the best, feeble. On this account
every care should be taken in carrying out the work after it
is planned, for, granting its arrangement to be good, it is just
possible a small fault introduced will have a disastrous effect.
The most common cause of this in new work is the introduc-
tion by inadvertence of some foreign material into the pipe.
Some men leave the ends of unfinished services open when
they leave their work, and something may chance to get in ;
or in the reverse case, when men temporarily plug the un-
finished end with a cloth or some such material, instances
have been known where it has been accidentally pushed in
and lost sight of.

It may not seem necessary thus to dwell upon the possible
careless actions of a workman, but it has to be remembered
that it is after the apparatus is finished and being tested that
the trouble first arises, and a very serious trouble it usually
proves. Firstly, it has to be ascertained what is the cause
of the bad or eccentric results. The workman has no know-
ledge of his blunder or oversight, and the true cause is
generally the last thing to be thought of, if it is thought of at
all. Usually the faulty part has to be located as nearly as
possible, and then the work has to be undone to a greater or
less extent. Difficulties of this kind are specially connected
with quite new work, but with an apparatus already in use a
sudden failure in some direction cannot usually be attributed
to defective workmanship, as it can be recognised as an in-
flexible rule that if an apparatus works efficiently once (under
ordinary conditions) any fault that may be developed after-
wards can rarely be blamed to the construction : it must be
due to some other natural cause, an obstruction for instance,
unless of course the apparatus has been subjected to an
accident.

The causes of erratic results are practically confined to

92 Warming Bitildings by Hot Water.

air, or the introduction of some foreign substance, which either
checks or for a time stops the circulation. In the latter case
it may be leaves or rubbish if ditch or pond water is used at
all carelessly. Of course there are other things that will
bring about an unexpected stoppage of work, such as a failure
in water supply, &c., but with an apparatus which customarily
works with steadiness and regularity any little unexpected
trouble is usually due to one of the causes named.

Water that is of a varying temperature is always under-
going a change in its aeration, absorbing and expelling air,
and on this account the air vents have more use than merely
allowing for an escape of air when the apparatus is first
charged. Every hot-water fitter knows that when first charg-
ing it is more difficult to expel the air from an apparatus than
is commonly supposed, so that it is quite understood that if
an apparatus is allowed to get a little short of water, so that
air enters one of the pipes, some trouble may ensue. When
once an apparatus is working with regularity every care
should be bestowed upon it to keep it so.

Hood speaks of the phenomena of hot water ascend-
ing the return pipe, and the colder water coming down the
flow ; that is to say, the water in an apparatus circulating
in a contrary direction to that which it is intended to do,
although the pipes are correctly connected at the boiler. " This,"
he says, " may arise in an apparatus having but a small motive
power, and in which the principle has not been followed out,
of making the water rise to the highest point as soon as
possible ; also having in the flow pipe much more pipe
and impediments than in the return, so as to create a greater
resistance by friction ; and having a greater bulk of water in
the ascending pipe than in the return ; and also with boilers
which are low in depth."

In horticultural works the quantity of pipe, &c., in main
and branch flow and return services, is usually about equal,
but when there are say five pipes, the odd one is put either in
the flow or return according to the judgment of the engineers,
some considering one way correct and some the other. In

Causes Affecting Circulation. 93

truth, it is doubtful whether with one single pipe there is any
noticeable difference either way. A large and well known
firm, who bear a high repute for this work in and around
Middlesex, always put the odd pipe into the flow, that is to
say, if a forcing house is heated by a branch flow and return
service containing five pipes, three would constitute the flow
and two the return. This has always proved eminently
successful.

This method, however, will appear to be opposed to
Hood's argument, but it really is not so, as he refers chiefly
to apparatus designed for warming buildings which have a
number of coils, radiators, or stacks of pipe in connection
with the main services, and with this he very rightly recom-
mends that, if not all, at least the bulk of these appliances
should be on the return. However, this subject will be dealt
with separately.

The reversing of the circulation is very likely indeed to
be due to the use of a very shallow boiler, in which a very
small distance exists between the points where the flow and
return pipes enter the boiler ; but this of itself would not be
sufficient to cause this phenomenon, though it would be
favourable to any other cause that might be active.
This, however, is an occurrence exceedingly rare, and in
horticultural works if the return pipe is found hotter than the
flow it may be taken for granted that an obstruction exists
air probably ; or that the supply of water is insufficient, and
the flow pipe partially empty.

In experimenting with a small copper boiler having a
system of circulating pipes in connection with it, the writer on
one occasion noticed that the circulation had started the wrong
way, and as the apparatus was constructed upon correct
principles, and had worked correctly on all previous occasions,
it was for the time rather puzzling to fix upon the real cause.
The first thought was that some unusual feature might exist
somewhere, as the apparatus by much alteration in experi-
menting had become rather complex, but examination proved
that the results should be normal and no reason appeared for

94 Warming Buildings by Hot Water.

the reversed circulation which was proceeding strongly all the
time. The last thing to be noticed was that the lamp was
not standing centrally under the boiler, but was giving all its
heat immediately under the return pipe. The return pipe
came through the top of the boiler, projecting down a few
inches inside. This was suspected to be the cause of the
fault, and further experiment with a simply constructed
apparatus showed conclusively that it is not at all difficult to
get a reversed circulation by applying the greatest heat to the
vicinity of the return pipe.*

In the majority of cases the return pipe enters the side of
the boiler, which arrangement greatly obviates the likelihood
of this trouble occurring. In very many cases, however, the
return pipe, when it comes into the boiler side, has to pass
through a flue where it feels a considerable heat, and if by
a blunder a vertical portion of this pipe was placed within a
flue or any heated position the effect of the heat would very
greatly favour a return circulation, and in any case it would
impair the efficiency of the apparatus, most probably ruin it.f

Perhaps amongst the phenomena that may be experienced
in this work, the most peculiar is the eccentric way an
apparatus will sometimes work in which there are, say two
branch services carried off from a main in contrary directions,
yet both starting equally, and both having about the same
amount of work to do. In an instance like this, every
engineer knows that it is the exception for the two services to
work equally, i. e. for both to heat up in the same time, and
both distribute an equal heat. Yet instead of one proving to
be more efficacious than the other permanently, it will
frequently be found that they will act to an extent alternately,

* These experiments were only conducted with a boiler having the
return pipe brought in through the top.

f Of course every practical man avoids carrying the return pipe into
any heated position. When it has to pass through a flue surrounding a
boiler, it is usual to cover it with brickwork, and there is one point in the
boiler where the pipe can enter and yet not be subjected to much heat,
although it passes through the flue, but in every case a covering of brick-
work should be resorted to. This will be more fully explained later.

Causes Affecting Circulation. 95

sometimes one taking the lead and sometimes the other, with-
out any apparent reason. Of course a remedy for this should
exist in every apparatus in the shape of a proper provision of
stop (or throttle) valves, which are inserted with a view to
the regulation of the heat to any desired degree at any point,
but apart from the remedy, the peculiarity remains at present
unaccounted for.

In this case it has been ascertained with tolerable certainty
that air is not the cause of the trouble, and it would be hard
to attribute it in any waylto irregular stoking. To the writer's
mind, the most feasible solution is that these instances of fitful-
ness of the circulation are due to variations in the weather.
In two houses, or two different positions, we must have one
more subject to external influences of heat or cold than the
other, and external influences always influence the apparatus
in the greater or lesser absorption of heat by the air from the
pipes. This would only happen to a noticeable extent with
branch services that have each about an equal amount of
work to do, and such is really the case, as services which differ
considerably from one another do not, as a rule, exhibit this
phenomenon.

In a small and simple apparatus it would not matter very
much which way the water circulated provided it was regular
in distributing a sufficiency of heat, but in a larger apparatus,
any irregularity must bring about some ill effect and annoy-
ance, to say the least.

96 Warming Buildings by Hot Water.

CHAPTER VII.

EXAMPLES OF HOT-WATER APPARATUS.

Describing some examples of the average apparatus A small apparatus
for a lean-to greenhouse Description of boiler Arrangement of pipes
Water Supply, etc. Another apparatus suited for a small conserva-
tory General description, position of boiler, etc., etc. Description of
another conservatory apparatus A larger apparatus to heat two glass
houses Pipes in channels General description A large apparatus
to heat a range of five glass houses with melon pits Main pipes and
their uses Carrying mains in trenches Branch services Pits with
bottom heat Evaporating troughs Capacity of air for moisture
Necessity of providing moisture Position of pipes as regards roots,
shrubs, &c.

IN studying a few examples, which we describe, of the average
description of apparatus that is to be met with, it must be
clearly understood that the illustrations are not made with a
view of providing designs to which other works can be erected.
In the first place, it would probably be found utterly impossible
to adapt any of them to a new situation. Secondly, it is best
and proper to work out and plan each apparatus that has
to be constructed in a manner best suited to the require-
ments, not giving any particular thoughts to previous under-
takings.

There is scarcely a doubt that of the many such works
erected in England there are not two precisely alike, so vary-
ing are the circumstances that have to be taken into account.
Still, those whose knowledge of such work is limited will find
considerable assistance from the consideration of an apparatus
practically complete and in position. A mere explanation of
the principles governing the work is hardly sufficient, unless
the reader has already had considerable practical experience.
After this chapter, appliances (boilers, materials, joints, &c.)
will be fully dealt with.

Examples of Hot-water Apparatus.

Perhaps the most simple form of apparatus that is ever
erected in connection with a boiler heated with coal fuel is
at Fig. 56. This is simply a flow and return pipe run up

Fig. 56.

along one side of a greenhouse, the pipes being most
probably 3-inch. This is a sort of apparatus used chiefly for
small amateur purposes, for a small sized glass house attached
to, or in the garden behind, a suburban residence.

The illustration shows a somewhat recent innovation as
regards the boiler. Previous to this form being introduced a
brick-set boiler would have been required, or else one of the
common independent form. In the latter case an objection
existed in that the boiler had to be in a sheltered position,
most probably in the greenhouse itself; in this case the pre-
sence of the boiler might not be so very objectionable, but in
the majority of cases the unsightly flue pipe had to have a
prominent position ; and in any case all stoking and attention
and the attendant dirt and dust, occurred inside.

The boiler illustrated is constructed in such a manner
that it can be fixed in the substance of the wall itself, as
Fig. 57, which shows a section of the wall with the boiler in
position. By this arrangement the flue pipe is conveniently
disposed outside, and all feeding, stoking and cleaning takes
place outside also. The pipe connections are. of course,
inside (as shown), and as there is no need in this case to place

Warming Buildings by Hot Water.

Fig- 57-

the boiler out of the way or in an inconspicuous position, it
can be placed (other circumstances permitting), so that the

pipe can be carried straight away, as
shown, and so save the cost and
other objections that the introduction
of bends and elbows brings about.

With this boiler there is but little
heat radiated from the body of the
boiler itself, as there would be if it
stood wholly within the house ; yet
even in this case there is little
actual loss, as the boiler, being im-
bedded in the wall, the poor con-
ducting property of brickwork pre-
vents the escape of heat, so that it

remains in the water and escapes from the pipe surfaces only
(excepting that which is radiated from the boiler front).

The other extremity of the apparatus is shown terminating
in a supply and expansion box, as recommended on p. 56
This contrivance cannot be overvalued, as it is so neat, so
accessible, takes the .place of the supply cistern and its neces-
sary connecting pipe, dispenses with the air pipe, saves a
connecting piece at the end, and provides a substantial sup-
port to one end of the apparatus. This appliance cannot
usually be made self-filling with the customary ball valve,
unless a small cistern be introduced, as the expansion box
itself is rarely made large enough to take a ball valve, which
requires an inconvenient amount of room. With an apparatus
on a small scale, however, an arrangement for self-filling is
not only unnecessary, but is a positive drawback, since the
evaporation being so slow and the loss of water so slight,
there is not sufficient work for the ball valve to keep it in
order. As most people know, this appliance works stiffly
and " sticks " if not in constant use.

In an apparatus even as small as this the pipes should be
made to rise towards the extremity, to assist the circulation
and to permit of the free escape of air. This can be effected

Examples of Hot-water Apparatus.

by standing the expansion box on a slight elevation (a tile or
some bricks) if necessary.

The use of this boiler necessitates starting the flow pipe
horizontally, and as the total difference between the highest
point in the flow and the lowest point in the return is but a
matter of inches, the motive power is small, and no obstacles
could well be permitted. It is not a boiler to recommend for
large purposes if fixed in the way shown. If such a boiler
be used below the greenhouse level, the flow pipe should be
taken from the top.

Fig. 58 introduces another form of apparatus almost as
simple in form as the last, but in this case it is supposed

Fig. 58-

that a greenhouse or conservatory attached to a residence
requires to be heated, but the boiler has to be situated in a
cellar or basement room of the house (in proximity to the
work).

On the left-hand side of the illustration is shown an inde-
pendent boiler of an ordinary form ; and as it is in this case
fixed below the level of the work, the flow pipe is taken from
the top, the return entering the side near the bottom as usual
These vertical independent boilers are admirably suited for

H 2

i oo Warming Buildings by Hot Water.

such a purpose as this, their shape making them convenient
as to the room they occupy, the necessary fixing is reduced
to a minimum, as they are quite independent of brickwork,
and merely require to be connected to the hot-water pipes
and to a chimney ; the latter is effected by a length of iron
pipe and an elbow. They are made complete with fire-box,
ash-pit, feeding and stoking doors, and only require to be
stood upon an earth or stone floor, or if the floor be wood, a
stone or concrete base has to be provided.

When fixing a boiler of this character it is necessary, to
make it work effectively, that the flue pipe fit on the nozzle
of the boiler tightly ; if it does not fit accurately, then let it
be jointed with stiff putty (ordinary glazier's putty). Where
the flue pipes are jointed together, and where the pipe or
elbow enters the chimney, the joints must be sound and tight
also, or a leakage of air or draught will take place into the
chimney with a proportionately ill effect. Every description
of close fire boiler, stove, &c., thus requires great care in
fixing, as all the air that passes into the chimney should first
pass through the fire ; if any other opening is left by which
much air can pass in, the draught through the fire will be
slackened and the boiler will not heat effectively. This will
be spoken of fully when treating of chimneys.

A vertical-shaped boiler is particularly adapted for holding
a charge of fuel which is delivered in through the feeding door
which is always situated at the top. Small horizontal boilers
do not meet this requirement quite so well, although these
can have a means of so doing if required, but hardly so well
as with the vertical shape. It will be readily understood that
in such a case as this it is very desirable that the boiler should
hold a store or charge of fuel sufficient to last a number of
hours without attention, as in all probability the stoking may
be done by a domestic servant. This end is met perfectly in
a vertical boiler, as a medium-sized one will hold perhaps
i^ bushel of coke, sufficient for twelve, or at least eight
hours ; and once the use of the dampers is understood, the
temperature can be kept at a regular point continuously.

Examples of Hot-water Apparatus.

101

Fig. 59-

Every boiler of this description has the stoking and ash
pit doors arranged so that they can be used as dampers or
draught regulators, but, unless carefully attended to, they do
not bring about such regular results as a sliding or throttle
damper in the flue pipe will do. Considering the small
outlay involved one of these latter should be provided in any
case, especially as they are better understood by inexperienced
persons.

Fig. 59 illustrates a sliding damper, this damper and its
frame being made in and part of a length of flue pipe. This
is by far the best of all dampers. Fig. 60
shows in section what is called a throttle
damper, being a disc of iron which by a
handle attached can be made to lie at any
angle to retard or to give free way to the
draught. This can not well be made to fit
accurately, and a great drawback is that
unless very nicely balanced it will not stay
in the position it is placed at ; it may by the
up current or draught swing open (or close),
and even if it fits well at first, wear, or ex-
posure, &c., will afterwards make it work
erratic.-

It may be mentioned here, although it will
again be referred to, that in charging these
boilers with fuel, some care or experience is needed parti-
cularly as to the size of the coke. When the boiler is filled
up with fuel it is with the view of providing a store of fuel
at the top to automatically replenish the part below as it
burns away. The automatic action is merely the gradual fall
of the upper material by its own weight as the lower is con-
sumed. Now every one knows with what tenacity pieces of
coke will cling together, and if we filled a small boiler with
pieces of medium size we should find that in many instances
it would refuse to fall freely, and although the lower part
burnt away, the upper part would wedge itself up and be-
come " bridged," as it is called. The maintenance of the fire

Fig. 60.

IO2 Warming Buildings by Hot Water.

depends upon the regular and gradual fall of the fuel, and this
is made certain by breaking the coke very small, that is, to
walnut size for conservatory boilers in general ; with large
boilers, of course, a larger fuel is permissible, as the
' bridging " does not take place so readily in a larger area.

On the right of the illustration Fig. 58 is shown an
arrangement of pipes that may be in connection with the
boiler just referred to. There is no need to show how the
pipes are carried through the space that may be between the
boiler and the greenhouse, as this will now be quite under-
stood. They are simply carried by the nearest route, and
care must be exercised to see that they do not dip down in
their course anywhere, but are either carried horizontally or
with a rising inclination. The connection of the pipes, how-
ever, at the boiler and at the commencement of the radiating
pipe is shown, and each pipe marked, namely, F flow, and
R return.

With this apparatus it has to be explained that the pipes
between the boiler and the greenhouse do not by any means
require to be large, certainly not the large cast pipes such as
will be fitted in the greenhouse itself, as these would be most
awkward to use, of greater expense, and quite unnecessary.
The pipes between the points named need not be larger than
i inch for a moderately small purpose, or ij inch or I \ inch
if the conservatory is of good size and has a fair quantity of
radiating pipe. Wrought iron tube is used for this ; it is easy
of adaptation, is neat, and very reasonable in cost.

In ordering the boiler it must be required to be drilled
and tapped for whatever size of pipe is to be used. The cast
radiating pipes have ends fitted to them which can be drilled
and tapped in the same way for connection.

The illustration shows three rows of pipes carried round
two sides of the house, two flows, and one return. Let it be
clearly understood that it is not always necessary to have
three pipes, in fact it is not usual, two pipes only, one flow
and one return, being generally sufficient and customary for
this small purpose. Three pipes are shown, however, to

Examples of Hot-water Apparatus.

103

illustrate the ordinary method of adding the extra pipe if
needed. For instance, suppose the conservatory to be used
only as an adjunct to a ball room, in which instance it might
be filled with hardy shrubs and heated only as occasion
demanded. In this case three 2-inch or 3-inch pipes would
give quicker and more economical results than two 4-inch
pipes, as has already been explained. Or, supposing the
conservatory to be a lofty one in regular use and having
sub-tropical trees in it, then two pipes would probably be
insufficient.

The pipes would be arranged so that the extremity where
the air pipe is situated is higher (by several inches if possible)
than where they first start off horizontally* after coming
through the floor.

When the pipes extend away around the house as these
do, it is very necessary that they have support at different
points. The nature of the support varies very greatly,
different engineers having different views upon the subject.
A very common method is to use brickwork, a small column

Fig. 61.

Fig. 62.

being built up to and around the pipes as Fig. 61. This is a
very good and workmanlike practice, but it is hardly admis-
sible if the pipes are situated in a conservatory fully exposed
to view, and recourse is then usually had to iron in some form.
A very good iron pipe-support is made, as Fig. 62. These
are made for any number of pipes one above the other, or they

* In speaking of horizontal pipes in this work, it is understood that they
are slightly rising towards one extremity.

IO4 Warming Buildings by Hot Water.

can be had suitable for two rows of pipes ranged side by side.
Another form is simply a wrought-iron strap bent to the
shape shown at Fig. 63 ; this, however, is only of use when
the pipes run along a wall or partition, as the
Fi s- 6 3- straps require to be secured to something at the
back of the pipes, as will be understood. When
the strap is used, a strip of wood is stood up
between the wall and the pipes, as it is not
desirable that the pipes bind firmly against
the wall ; in fact, they should hang in mid-air,
so to speak, so that free radiation of heat from
the whole of the pipe surfaces be assisted. Of
course, any other form of support is permis-
sible, provided it is of firm bearing, not likely
to lose its shape or rigidity. Some care must also be ex-
ercised to see that the foundation to the support is good, or
the weight of the pipes or some other cause may make the
support sink and the pipes become uneven and out of level.
This occasionally happens with brick piers, which are weighty
in themselves, and if placed on the earth without care may
soon sink down to some extent.

The cold supply to this apparatus need only be provided
for by a small cistern, filled by hand, as the loss by evapora-
tion would be so trifling, insufficient to make the use of a
ball valve at all necessary. This small cistern should be
placed at the most convenient spot, out of sight if possible ;
or, if not, it may be fastened on a wall and decorated, but it
need only be just above the level of the highest point of the
flow pipe. It is never a good plan to place these cisterns
more than, say 3 feet (a few inches is sufficient) above the
point mentioned, as there is no need for it ; it makes the
regular replenishment a little more troublesome and more
likely to be overlooked, as the want of water could not be
observed so readily ; and, lastly, it increases the strain upon
the joints and apparatus generally. (See Pressure of Water
in Pipes, p. 255.)

The cold supply pipe need not be larger than half-inch in

Examples of Hot-water Apparatus. 105

a small apparatus like this, and it should be carried and con-
nected into the return pipe near the boiler, or into the boiler
itself, otherwise the contents of the cistern will probably get
heated (notwithstanding the dip in the pipe), and vapour will
rise from it. This would not very much matter in some
instances, but it is not desirable in a conservatory. If, how-
ever, the boiler is a distance from the work, then the cold
supply may enter the return pipe at some other point, but let
it be as much below the radiating pipes as possible. In any
case the customary dip is needed in this pipe close to where
it enters the return, and this dip should be about 12 inches
deep if possible, to prevent the heated water travelling up this
pipe as has been already referred to.

Although the dip in the cold supply pipe is necessary, and
is supposed to appear in every apparatus that is rilled from a
cistern, there is one noticeable drawback, namely, the liability
of this dip becoming choked with dirt which cannot be washed
out or removed without taking the pipe to pieces. This is
greatly aggravated by the practice of leaving the lid off the
cistern, so that dirt and matter finds its way into it, and
this eventually reaches the dip where its further movement is
stopped, and should rain water be used, there is even a greater
liability of stoppage, as will be understood. This drawback is
quite recognised, and occasionally preparations are made for
its cure ; but the only remedy that is at all worthy of recom-
mendation is the provision of a screw plug at the lowest point
in the dip, and if the dip is abrupt, that is to say, the two
pipes close together, then a stoppage can be readily disposed
of by the insertion of a wire or cane.

The next apparatus, Fig. 64, exhibits an arrangement
differing from the last, as it is desired to heat a small glass-
house or conservatory around all four sides. It cannot be
arranged for the flow and return from the boiler to be con-
nected at either of the extremities of the radiating pipes, and
consequently the apparatus becomes one having, to all intents
and purposes, branch services from the primary or main flow
and return pipes. A certain care then becomes necessary to

io6 Warming Buildings by Hot Water.

arrange for the branch in each direction to heat equally or at
any rate to work without a noticeable irregularity.

In this apparatus, as with the last, it has to be explained
that an unusual feature is introduced, as it is rarely necessary,

Fig. 64.

.s_

i->

and more rarely customary, to heat (i.e. carry pipes around)
all four sides of a conservatory ; but the illustration will serve
to explain how to treat these branch services, whether they
extend as far as shown, or a less distance.

We may suppose this apparatus to be heated by a small
independent boiler placed in a basement or some such point
contiguous to the work, but, of course, below the conservatory
floor level. From the boiler to the radiating pipes there need
only be a i-inch or ij-inch flow and return, connected and
dealt with in every way as described with the last apparatus
and in Fig. 58, and the pipes are marked F and R in the
same way as in the preceding illustration.

We may suppose that this house is not very large, in
which case, if the pipes are carried all round, 3-inch would be
sufficient. This is governed by various circumstances, and
recourse must be had to the rules and calculations provided
to determine quantities, sizes, &c., for heating certain areas

Examples of Hot- water Apparatus. 107

and for certain purposes. This subject is dealt v/ith fully in
Chap. XL Should the calculations prove that a third pipe is
requisite or desirable, this can be added as explained in the
last apparatus, that is two flows and one return. If it were
thought best, one branch might have two pipes as illustrated,
and the other three, that is two pipes round one end of the
house, and three round the other ; but this is quite an excep-
tional requirement.

It will be noticed that one branch has to travel farther
than the other, as the primary flow and return does not enter
at an equal distance from the door either way. Consequently,
if some care is not used, there will be every likelihood of the
shortest branch " taking the lead " as it is termed, that is a
rapid circulation setting up in the short branch to the preju-
dice of the longer one, and causing the circulation in the
latter to act sluggishly and to be of less heat-giving efficiency
than it should be. In a large apparatus this is fully expected
with some of the branch services, and provision is made for its
proper regulation by means of throttle valves, the faster
heating services being checked that the sluggish ones may
attain a normal circulation and so on, according to the wishes
and requirements of the gardener. But in a small apparatus
such as we are discussing, the use of regulating valves for this
purpose is unnecessary, normal and sufficiently regular results
being easily obtainable by giving a greater rise to the long
branch than the shorter one, and this greater rise will be found
to counteract the greater resistance that the increase of length
offers.

At the highest extremity of each branch an air outlet has
to be provided as shown, these being connected and carried*
in one of the manners described on p. 82. The pipes have
also to be supported well and securely, as described with the
last apparatus explained.

As the work gets larger, attention must be given to the
question of expansion, as although in a small apparatus the
elongation of the pipes when heated is so trifling as to be
unnoticeable, yet in a large one, where long runs of pipe exist,

1 08 Warming Buildings by Hot Water.

consideration must be given as has already been explained,
but it is only in what we may consider very long lengths, that
rollers and frictionless bearings on the supports are needed.

When pipes are supported on any of the iron stands
referred to, there is so little friction that a moderately long
length of pipe moves easily upon it as the expansive force, or
the reverse is exerted ; but in brick piers the resistance by
friction is greater, and with these, roller bearings for the pipes
would be needed with a shorter length than if the supports
were iron properly constructed with the bearing surfaces
reduced to a minimum. But the fact of building a brick pier
support around the pipes as explained and shown in Fig. 61,
does not materially increase the friction over a plain brick pier
which would not cover the pipes, as it will be found that when
once the apparatus is heated, which to a trifling extent
increases the girth of the pipes, the brickwork will no longer
firmly bind upon the pipes, and any movement lengthwise
will experience no particular resistance, the brickwork
having ceased to hold the pipes with any degree of tenacity.

The cold supply should be provided for and connected in
the manner described with the last apparatus, and reference
should be made to Chapter III.

The next form of apparatus, Fig. 65, we may describe, is
one in which the work is a step further than that just com-
pleted, and one in which we may suppose there are two glass
houses to be heated, these houses joining one another end to
end as is customary, but requiring different temperatures for
different purposes, this being the primary reason, of course,
that there are two houses instead of one larger one. Although
these houses are spoken of in the plural sense, it will be found
in almost all cases that the erection, in reality, is but one
house, with a division in it, so that plants or fruit requiring
different temperatures, &c., may each have the distinct treat-
ment and an atmosphere which is most congenial to them.

When the house is divided in this manner, the partition is
commonly of wood and glass, but, whatever it is composed of,
there is always (there may be exceptions) a doorway in it,

Examples of Hot-water Apparatus.

109

and this interferes with the carrying of the pipes all round the
house in anything like a simple manner, as in addition to the

doorway in the partition we may as a rule expect to find a
doorway in each end also as shown. Of course, a doorway

TOT

USI7BR5ITY

1 1 o Wanning Buildings by Hot Water.

can be passed by dipping the pipes ; but this plan is very rarely
resorted to in practice, it is not natural and under the best of
circumstances it is in some degree prejudicial to success ; and
perhaps one of the greatest objections to it is that a dip in a
pipe must prove a collecting point for dirt, and is rarely
accessible for easy cleaning even if such a provision is thought
of. It is quite customary, with an apparatus such as we are
describing, to carry the pipes around one-half of the house as
far as the doorways will permit, this half being on the most-
exposed side. As glasshouses are so often built against a
wall there is no noticeable objection to this arrangement,
supposing a very high temperature is not needed.

When a high temperature is required, arrangement is then
made (if possible) to carry the pipes on all sides, and some-
times also up the centre, every available point having pipes if
the house is for tropical plants or fruits, orchids, &c. Unless
there is some very strong objection, it is always arranged for
the hottest house to be nearest the boiler. It is exceedingly
exceptional for this latter arrangement to be impracticable, as
upon the erection of hothouses every forethought and care
is given to their being successfully heated, and, as before-
mentioned, it is the regular thing for the gardener to superin-
tend and to direct the works generally.

The illustration represents two houses, which we may
suppose are of fair size, situated against a wall at the back,
and having a passage-way through the centre, thus introducing
a door at each end, and one in the division as shown. The
boiler (of saddle or any customary shape, or it may be of the
independent kind, although this is not usual), is fixed in a pit
at one end near to the wall, or it could be on the other side of
the wall if more convenient or desirable. The pipes in this
case would be of full size where connected to the boiler, and
continued of full size throughout the apparatus, 4-inch being
the most suitable for work of this size and character, or 3-inch
is permissible if specially wished for.

In this case the pipes from the boiler would need to enter
the house below the floor level (the top of the boiler being

Examples of Hot-water Apparatus. 1 1 1

12 inches or more below this point). Immediately where
they enter close to the wall they require to be branched, one
branch instantly rising and being carried along the back wall
(one flow and one return), and around as far as the middle
doorway, as shown. The other branch is carried along inside
the end of the house nearest the boiler, but still below the
floor-level until the doorway in this end is passed. This
pipe thus carried adds its proportion of heat to the total
result, as it is placed in a brick or tile trench, and covered
with an open grating.

When pipes have of necessity to be placed in channels
or trenches, allowance must be made for lessened results due
to absorption of heat by the surrounding brickwork, &c.
The top gratings should be easily removable, as on no account
must the pipes be allowed to get coated with dirt, nor must
dirt be allowed to accumulate around them, as they would
then cease to distribute heat and might as well be covered
over entirely without the expense of the trench and grating.
Pipes in trenches, however carefully attended to, do not add
to the heat of the atmosphere in an equal proportion to the
pipes that are out of channels, and in calculating quantities
this must be remembered and allowed for (particularly in
church work, &c., in which exposed pipes are not permissible
except to some trifling extent where they are hidden from
view). This will be found more fully explained in the calcu-
lating tables.

The illustration shows the branch (from the boiler towards
the front of the house) carried in a trench along the full
length of that end before it is elevated, but it will be under-
stood that the elevation may, if desired, take place im-
mediately it has passed the door. Immediately the pipes are
brought up out of the channel they are carried along the
front of the house, but upon the supposition that considerable
heat is needed, the flowpipe is shown with an extra pipe
added, this being usually required in a tropical house, and
oftentimes when the house is of good size and cannot have
pipes on all sides.

ii2 Warming Buildings by Hot Water.

The branch now being spoken of may consist of four or
even six pipes. This branch, as already explained, is carried
along the front of the house as far as the division where it
turns, and is continued as far as the door. At this extremity
the three pipes are reduced to two, which are carried through
and back along the division on the other side in the other
house, and there continued along the front and around the
further end as far as the door, as shown, this house being we
may suppose for more hardy plants a greenhouse, in which
case the two pipes along the front and halfway up each end
will usually give a sufficient heat.

At the point where the three pipes of the hothouse are
reduced to two and carried through into the greenhouse,
there is the possibility of unsightly work being introduced
unless a box end is introduced. This gives much more
sightly results, and also to some extent reduces
the labour, it also forms a support at this point,
where one is much needed. This box end is similar
to Fig. 66 which shows three pipes entering at one
side and two leaving at another side at right angles
as would be required in this case.

It must not be forgotten that throughout this
apparatus (and throughout all that may be erected)
the pipes must be fixed to have a gentle rise all
the way from the point nearest the boiler to the
furthest extremities. This has already been insisted upon,
but it is desirable perhaps to repeat it.

In an apparatus that extends through two or more houses
it is necessary to introduce stop-cocks or valves to regulate
the heat, &c. In such an undertaking as we have now under
consideration it may be supposed that the heat in the green-
house may not be required during mild weather, yet in the
hothouse heat is necessary even during the summer, and in
such a case a means must be provided to partially or wholly
check the circulation beyond the partition. This would be
effected by inserting stop-valves of some description (see
pipes, fittings, and appliances), in the two pipes immediately

Examples of Hot Water Apparatus. 113

where they enter the greenhouse through the partition, as in

Fig. 67, which shows the box end already referred to, but with

the stop-valves attached to the two pipes just as they enter

the greenhouse. The cocks are thus

situated so that they effectually bring

about the result desired, yet they do

not, when closed, interfere in the least

degree with the circulation in the

first house. This is a very necessary

consideration.

Stop-cocks and valves can be had in
any size, but in such an apparatus as
this there is no need whatever to have
them of the full size of the pipe

2-inch will be sufficient without any risk of impairing the
general efficiency ; as in a small undertaking, rapidity of
circulation is of no moment, the extent of the services
being limited, and a very rapid circulation would only tend
to convey the hot water back to the boiler for no good pur-
pose ; whereas, if we check the circulation in a small appa-
ratus we get a stronger motive power by reason of a
greater difference in the temperatures of water leaving and
entering the boiler, and this at no risk of diminution of the
heat evolved. It must not be forgotten that the chief reason
for using smaller stop-valves is the lessened expense, these
articles being rather expensive if of good quality. The
use of smaller stop-valves, however, has to be made with
discretion, it lies chiefly with the distance that the pipes
have to travel after leaving the boiler. If the work is of
great extent every care has to be used to prevent the cir-
culation being checked as it is of no use having the water
travel a great distance if it is barely warm when it arrives.*
The same care has to be bestowed upon the question when
the circulation from some cause is sluggish. Air vents are

* The majority of gardeners are now rather averse to very extensive
runs of pipe, preference being given to the use of a second boiler. More
reliable results and oftentimes greater convenience is experienced.

H4 Warming Buildings by Hot Water.

needed at the highest points as a matter of course. There
is one shown at the box end at the division of the houses ;
this is necessary, as will be easily understood from the
illustration.

From the doorway nearest the boiler there is shown a
trench and grating carried up the middle of the house as far
as the division doorway. If it is thought necessary two (or
more) pipes may be carried up in this direction, in this man-
ner, this service being a branch from that which is carried
beneath the floor level past the doorway. To keep the trench

as shallow as possible, the two
pipes should be carried side by side
as in Fig. 68. This at any time
giving better results than pipes
one above the other, if they are in
trenches, or in some cases the cost
of trenching can be avoided, and

the pipes run along in the open at the side of the path or
footway as in Fig. 69. This service would require an air outlet

Fig. 69.

Fig. 68.

at the extreme end, which of course is understood to be the
highest point ; but this air pipe need not be carried up inde-
pendently, it may join any other air pipe that is nearest to

Examples of Hot-water Apparatus. 115

it, but as already explained it must not be allowed to dip
down anywhere, but must ascend all the way.

The cold supply to this apparatus would be provided for
by a cistern (with cover) in the usual way, the service pipe
from the cistern being connected into the return at a near
point to the boiler, or into the boiler itself. There is, however,
an objection to taking the cold supply into the boiler in an
apparatus like this, inasmuch as, unless special provision be
made, some difficulty will be experienced in disconnecting it,
which is very likely to become necessary as the dip or
" siphon " in this cold service so commonly gets stopped with
debris. The cold supply pipe in this case would not be larger
than |-inch (some may use ^-inch), and this readily be-
comes stopped at the dip, where dirt quickly collects, if pond,,
rain, or ditch water is used for rilling. On this account it is
desirable to keep the pipe clear of the brickwork surrounding
the boiler, so as to be readily disconnected if desired, yet at
the same time let it be attached to the return pipe at as near
a point to the boiler as possible.

It has already been mentioned that one reason for bring-
ing the cold supply into the return near the boiler is that it
may enter where the coolest water is, and so the contents of
the cold cistern be least likely to become heated ; but in an
apparatus such as this it becomes necessary to have the cold
supply somewhere on the boiler side of the division between
the two houses, as, were it connected to the pipes in the
greenhouse, the water supply (as well as the circulation)
would be cut off when the stop-cocks were closed.

The branch that is carried round the back of the hothouse
should not be given much rise, so that the circulation in this
direction may not outdo that in the other direction, where it
has more work to do. It is hardly necessary to insert stop-
valves* in this back branch, if it is kept nearer the horizontal

* The names " stop-cocks " and " stop-valves " have hitherto been used
indiscriminately, but the different uses they are intended for will be
explained when treating these articles and appliances generally.

I 2

1 1 6 Warming Buildings by Hot Water.

than the other ; this usually proves sufficient check in a
moderate-sized apparatus like this.

We can now proceed to describe another form of apparatus
as illustrated in Fig. 70,* which is upon a still larger scale
than those already treated and which introduces a new
feature that usually becomes necessary when more than two
houses are heated from one boiler. This particular feature is
the " main " service, which is practically a primary flow and
return, the general work being done by a number of branch
or secondary services from it.

The real uses of this main service are twofold, firstly, if
say four houses in a. line were required to be heated from one
boiler it would be impossible to hope for anything like good
results from the house furthest from the boiler if the circula-
tion had to work through all the ramifications of the pipes in
the first three houses. In fact it is doubtful if any very good
results would be obtained in the third house unless cir-
cumstances happened to be propitious. Secondly, if the
pipes were continued from one house to the other as just
described it would be impossible to close the stop-valves in
any one house without seriously interfering with the heat in
the houses beyond it ; and it is absolutely necessary that
each house have means to regulate its heat without in any
way prejudicing the results in the others.

In the illustration, Fig. 70, the main pipes are shown
carried along the front of the first three houses with the view
of affording heat to some melon pits as shown ; this is a
very common practice and there is no objection to it, but if
the melon pits did not exist, then the main pipes might
be carried up the middle of the houses in a channel, or

* These illustrations are of houses which are bounded upon one side
by a wall. This is an arrangement usually sought for, but not always
possible, particularly in large professional growers' grounds where there
are ranges of houses side by side, necessitating the use of what are known
as span houses, and which, on account of their width, usually have pipes
carried along each side instead of on one side ; and when the house is of
good width, there may be pipes carried up the centre (under the stages) as
well, as there would be a foot-way on each side.

Examples of Hot-water Apparatus.

117

1 1 8 Warming Buildings by Hot Water.

better still, they might be carried along the outer side of the
back wall (on the same side of the wall as the boiler.) See
p. 120.

In any case the main pipes should start as far below the
level of the house floors as conveniently possible so as to
afford a gentle rise along their full length. In addition to
this, allowance has to be made for each branch service to rise
a little after leaving the main, and to effect this it would be
very desirable in a large undertaking like this to have the
boiler top 2 feet below the floor-level of the houses if possible,
but this is very usually governed by the nature of the ground,
as in some situations water is met with a very little way below
the surface, and a deep boiler pit is out of the question.

If the boiler pit cannot be of ordinary depth by reason of
water being found near the surface, it becomes necessary to
use one of the several forms of shallow boilers which are
made expressly for this emergency (see Boilers, p. 205). Or
perhaps the houses may be placed on sloping ground so that
a rise is naturally required for the pipes as they go from
house to house this arrangement obviates the necessity of
putting the boiler lower than is barely necessary to start the
pipes horizontally into the first house.

The main pipes, in this latter case, need not be lower than
the floor-level unless it is necessary to carry branches beneath
doorways, &c. ; but should the houses be quite level and
extend a good distance, as these do, then it is desirable to
start the main as low as possible so as to give it as much rise
as can be obtained in its journey to the extremity of the
apparatus. When the houses are on rising ground this latter
necessity does not arise, but it is the customary and generally
desirable plan to carry the mains below the floor level some
little distance. In the apparatus under discussion the melon
pits, through which the mains run, are a little lower than the
houses they lean against ; this is arranged and planned in
concert with the gardener's wishes and ideas.

There used to be a controversy as to the correct size of
main pipes, one suggestion being that the proper sized pipe

Examples of Hot-water Apparatus. 119

to use was one having a sectional area equal to the aggregate
areas of the branch services, that is to say, if there were eight
branch services of 4-inch pipe, then the main pipes should
have a sectional area equal to the combined areas of eight
4-inch pipes. It is needless to add that this would make the
mains of enormous proportions. Theoretically this argument
carried weight, but in practice it was all wrong. The large
size was most inconvenient and costly, the extra quantity
of water contained in such large pipes was unnecessary and
objectionable in other ways, and it was found that 4-inch
mains were ample even for the most horizontal works, and
even 3-inch mains have been found sufficient where a more
than usual rise and fall has been attainable and in residence
work where a deal of vertical pipe exists the mains rarely
exceed 2-inch, and are not commonly as large as that. The
greater the rise and fall the less size the mains need be, but
in horticultural work 4-inch is usually necessary, in fact it is
the recognised size for this purpose.

The chief reason why a 4-inch main answers so well is
that in a pipe of this size which has but few bends and a
gradual rise from the boiler to the extremity, there must be
necessarily a fair rapid circulation and this fulfils all that a
main service is required to do, viz., carry a supply of hot-
water to the required points quickly, and the cooled water
back to the boiler in an equally short time. The branch
services from the mains do not require to have a particularly
rapid circulation, for so long as the heated water finds its way
into the house, and then out again before it is absolutely
cool it suffices, for it passes in with the view of dissipating its
heat there, and no great gain is effected by its going in and
out too quickly. A circulation can of course be too sluggish,
but if the branch return, as it leaves the house, is found to be
just warm, the rate of circulation is sufficient.

If the mains are carried up the centre of the house in
channels, they should be covered with loose gratings (as ex-
plained in the last apparatus) so as to benefit by their useful
effect, and in such a case allowance may be made for the

I2O Warming Buildings by Hot Water.

presence of the mains in the house, when calculating the
quantity of pipe needed, but it will be remembered that pipes
in channels do not radiate more than three-fourths the heat
that exposed pipes do (see p. 245).

If the mains were carried along the outer side of the
back wall, they would then be carried in a brick channel, but
a quite new feature is introduced here, as there should in this
instance be no heat radiation from the mains themselves.
Were this the case the heat so radiated would be wholly lost,
without the least beneficial effect, and consequently means
have to, or should, be resorted to with the view of conserving
the heat within the pipes, and only permitting radiation to
take place from the pipes in the houses where the heat fulfils
its useful purpose.

The conservation of heat is a very interesting and im-
portant subject and requires every consideration, but it is not
necessary to speak of it at length here, as it will be found fully
discussed in Hot Water Supply, p. 329, and Independent
Boilers, p. 156. However, some necessary measures may with
advantage be spoken of in this place.

If the mains are carried along the outer side of the wall, it
may be assumed that the earth on that side is upon a level
with the house floors, in which instance the pipes will have to
be carried underground. This being the case it is usual to
make a brick trench or channel, in which the pipes are laid,
the channel being afterwards covered with slates and the
earth filled in on top of these. This makes the pipes easily
accessible if it is desired to expose them, but it is also
necessary that the space around the pipes in the channel be
filled in with some poor conducting material, otherwise it is
just possible that a current or circulation of air may set in
through the channel, and this would have a rapid cooling
effect upon the pipes, as will be understood.

Of course a current or passage of air through the trench
could be prevented by making it perfectly air-tight ; but this
would be a greater trouble and expense than filling it in,
especially as good materials for this purpose are so cheap.

Examples of Hot-water Apparatus. 121

Perhaps one of the best materials is dry sand. Silicate
cotton is better, but a quantity of this would become expen-
sive. Hair or even sawdust would do, but the former is
expensive and the latter absorbs moisture. Sand is most
commonly used and answers well, and is most easy of applica-
tion ; little wood fillets can be placed across the channel here
and there for the pipes to rest upon, and this will then permit
the sand to get under the pipes also. There need never be
any fear in letting these pipes come in contact with wood, as
no possible danger can arise, although the Building Act
classifies them with flues and other possible causes of a
conflagration. The Act, however, is not at all strictly adhered
to with hot-water pipes, and there is no occasion for the pre-
caution in the way the Act puts it ; but it is just possible that
in framing these provisions a thought was given as to what
would happen should the apparatus be used, by some extra-
ordinary oversight, without any water in it, as in this case the
pipes near to the boiler would become of a very high tempera-
ture, sufficiently so to ignite any inflammable material that
might be in contact with them, in the same way that an
over-heated hot-air apparatus would do.

Branch Services. In this apparatus, as in the last, the
mains after leaving the boiler are carried across the end of the
house below the floor-level, in a brick trench covered by a
grating. In the first house, which is assumed to be for tropical
plants, there is shown a branch of three pipes, two flows, and
one return across the back of the house and around as far as
the doorway in the division ; also a branch of a similar
character across the front of the house and around to the
division doorway, and a branch of two pipes carried up the
middle beneath the floor in a channel covered by a grating.
This is usually ample for a tropical house, but the reader is
again reminded that the sufficiency of pipe is determined by
calculation as described hereafter (p. 238).

The pipes in this house (and throughout the whole ap-
paratus) will be 4-inch, and an air-vent would be needed at
the highest (i. e. furthest) extremity of each service.

122 Warming Buildings by Hot Water.

In the second house, which is reserved for a certain kind of
grape and for strawberries, it will be found sufficient to carry
the pipes across the front and around each end as far as the
division doors, these pipes being connected to the mains by a
branch brought across the melon pit as shown ; and in this
case it is supposed that the vine roots are at the back of the
house near the wall. In this grape-house there are shown
four pipes, two flows, and two returns, this particular variety
being supposed to require a higher temperature than that in
the next house which has a pipe less. It does not, however,
fall to the hot-water engineer's lot to decide what temperature
a certain variety of fruit requires, this being determined by
the gardener, who (it cannot be repeated too often) decides all
such questions and dictates generally.

To this second house there would need to be a pair of
stop valves ; one in the flow, and one in the return, where the
pipes pass across the melon pit before they enter the house,
and before the branch is increased to four pipes. No valves
were mentioned in the tropical house, it being a somewhat
disputed question as to whether they are needed there, many
gardeners affirming that no regulation is needed in that house,
too much heat being impossible, and others having an opposite
opinion. If cost is not of primary importance, it is best to
have valves in every branch that is of the least importance.
In this second house there would need to be the usual air
vents at the furthest extremity of each end of the branch, that
is the end by each doorway.

The third house is supposed to be devoted to grapes of
another variety requiring a lower temperature, and possibly
a slightly different atmosphere, which renders it difficult for
the two varieties to be grown together, and so necessitates a
separate house to each.

In this case there would possibly be two flows and one
return running along the front of the house and up each end
to the doorways, the necessary air vent being provided at
each of these ends ; but in this case we may suppose that the
roots of the vines are differently disposed, and instead of

Examples of Hot-water Apparatus. 123

being situated at the back they are brought through the front
of the house, the roots themselves being in the earth outside
the house, but the stem or trunk being trained through the
front of the house into the inside, where the whole of the
vine may be said to exist, except the roots. This is a most
common practice, the famous vine at Kew being trained in
this manner, and it is to be presumed that it gives favourable
results, although it interferes somewhat with the disposition
of the hot-water pipes.

If the house abuts against a wall, it is very properly sup-
posed that that side nearest the wall is in least need of heat,
or, rather, it loses its heat less quickly ; and if one side of the
house only is encircled with pipes, then it should be that side
which is most exposed, and this would be the side furthest
from the wall. If, however, the vines enter through the front
then some remedy has to be sought, and commonly the little
problem is solved by putting the pipes along the wall side.
This, however, is not the best plan, a better one being to run
the pipes along on stands or supports just in front of the vine
trunks. Provided the pipes are kept away six inches no harm
will ensue from this, and it will give as good results as any
way, and certainly better than carrying the pipes along the
back wall. In this case stop valves would need to be fixed
in the branch flow and return as they cross the melon pit, as
explained with the last house.

In the next, which may be termed a greenhouse, three
pipes two flows and one return across the front only
without returning up the ends, usually suffice, these being
connected from the main, as before described, with the neces-
sary stop-valves and air exits. A greenhouse is generally
used for plants, sub-tropical productions, or orange trees, &c. ;
but the term greenhouse does not convey any very exact
meaning, and consequently the quantity of pipe will be wholly
governed by what the gardener intends stocking the house
with.

The last, and which would be called a cool-house, has
two pipes only, carried along the front. This house would

124 Warming Buildings by Hot Water.

only be used for wintering trees or hardy plants, or for
apricots, tomatoes, &c., that only need to be preserved from
frost

This house will not require to be in direct communication
with the mains, and if the pipes are continued through from
the greenhouse this will be found quite satisfac-
Fig. 71. tory, but there will have to be an H -piece with
valves, just at the division between the houses
as Fig. 71 ; this provides a means of closing off
or regulating the heat in the house. An air-exit
must be provided at the extremity of the two
pipes, at which point the apparatus reaches its
highest level.

The pits along the fronts of the houses, which
are generally devoted to melons and cucumbers, are heated by
the two main pipes which pass through their whole length, and
also by the branch services which cross them. There is, of
course, no means of shutting off or regulating the heat of the
mains except by the regulation of the fire under the boiler,
so that if the pits are at too high a temperature (they are
never too cool with two 4-inch pipes through them), recourse
is had to the lights or covers, which are opened to a greater or
less extent, and so permit the heated air to escape,* and thus
reduce the temperature within. These pits are lower than
the houses, this being arranged in the construction, which
gives every facility for the gentle ascent of the pipes from
beginning to end.

This apparatus will consist wholly of 4-inch pipes, and it
may be said that the work here shown is as much as should
ever be put upon one boiler. With any apparatus larger than
this two boilers would be desirable, and would give more
satisfactory results. In an apparatus such as this the pipes
would be supported by brick piers or by iron stands ; brick-
work is most usual, although of the two iron has the best

* It takes but a very little time to reduce the temperature of a pit, as
immediately the cover is shifted the warmed air, by its rarefaction, is dis-
placed by cold air, and a change in temperature is directly effected.

Examples of Hot-water Apparatus. 125

appearance and as much solidity. In any case, the founda-
tion or ground upon which the supports rest must be firm,
and have no tendency to sink in the least degree.

The next and last apparatus that it is intended to describe
(in this chapter) is as Fig. 72, Very little space need be
taken up in describing this, as it only differs from the previous
ones in having one (or more) houses cut off from the others
by reason of a doorway coming in the wall at the point shown,
and assuming the boiler has of necessity to be placed at the
point here indicated instead of at the end of the houses, as in
the other undertakings described.

It is not, of course, absolutely necessary that the boiler
be at one extremity of the houses to be heated ; in fact, by
placing the boiler somewhat centrally, we may occasionally
gain a little in convenience. Here again, however, we have
to act agreeably to the gardener's planning ; no one is more
capable of deciding such questions ; but let it be understood
that he is not to be appealed to in everything, the worker
must have judgment of his own. At the same time, if there is
a gardener on the premises, as there nearly always is, he
must be consulted and his wishes carried out. In most cases
the gardener superintends the work to a very considerable
measure, and everything is done in accordance with his views ;
indeed, many gardeners are highly skilled in planning such
works.

In the arrangement just referred to (Fig. 72) it becomes
necessary to have two sets of mains, so to speak ; that is to
say, the main flow has to be branched off in two opposite
directions immediately it leaves the boiler, or, if desired, two
distinct flows could be taken from the boiler direct ; in either
case the pipes should be 4-inch, no larger nor smaller becoming
any more desirable by either arrangement.

In the illustration it is supposed that there is one house
on the left of the doorway, and two or more on the right, and
that no pits exist in front of the houses. In this case the
main to the left may be carried along the outer side of the
wall, below the ground level (thus clearing the doorway),

126 Warming Buildings by Hot Water.

until it reaches the nearest end of the house, where it passes

through the wall inside and is disposed of for heating pur-
poses in some one of the
various ways already spoken
of, or as circumstances or
judgment may dictate. The
return pipe would be brought
back into the side of the boiler,
and although the two main
flows may be branched from
one pipe there is no need
whatever for the returns to
be joined in any way ; the
two returns come one into
each side of the boiler, this
arrangement giving the most
uniform results generally.

On the right-hand side of
the boiler the main service is
shown carried along the outer
side of the wall as described
on p. 1 20, and from this the
branches are taken through
the wall into the houses at
the points desired ; this has
been fully described also.
From this last main service
there is shown a branch 01
supplementary main service,
carried off at right angles
near the boiler for the purpose
of heating another house
which we may suppose is a
few yards away. This can
be done in the way shown,
or supposing this service had

its starting point anywhere near the boiler it might be

taken direct from the boiler itself.

Examples of Hot-water Apparatus.

127

It would be rather necessary to have stop-valves in each
pair of main pipes (as well as in the branch pipes where
usually needful) with the view of regulating the circulation in
each direction. It would also be very necessary to carry and
surround these main pipes in the way described (p. 120), as it is
supposed that they are wholly underground. And there would
need to be the customary air-exits, and other provisions already
spoken of fully in the previous works described in this chapter.

In the majority of hothouses of any pretension, there
should be a pit with water pipes beneath it, to be used for
forcing purposes, also in the cultivation of pine-apples, &c.
This description of pit must not in any way be confounded
with a pit that is a space dug out of the earth : those now
referred to usually stand above the level of the hot- house floor-
There are three or four arrangements for heating them ; * one
being as in Fig. 73, in which the earth rests upon a sort of
false bottom full of perforations, the pipes being disposed
beneath as shown ; or in another case the pipes are laid within
the pit at the bottom, as in Fig. 74, these being first covered

Fig. 73-

Fig. 74-

with clinker, large stones, or broken bricks, and the earth being
placed on top of this large material. Sometimes the lower
part of the pit contains water, the earth resting on a perforated
false bottom above it, as in Fig. 75, the pipes passing through

* By adopting hot-water pipes for this work, the use of manure and such
heating matters is avoided, with all the consequent inconvenience, irregu-
larities, &c.

128 Warming Buildings by Hot Water.

the water as shown. The part containing water is usually
made of brickwork well cemented to render it water-tight-
It will be understood that when first starting the apparatus the
water in this tank robs the pipes of heat very rapidly, but once
the water is hot it is kept in that condition with very little
expenditure of heat. This arrangement is also adopted for
heating a tank of water for watering purposes, but in such a
case there are usually valves, so that the water does not
always circulate through owing to the cooling influence it
would have as the water in this tank is drawn off, and replaced
with cold. Frequently, therefore, the valves are only opened
at such times as the heat can be most spared at noon for
instance, when natural warmth is at its highest In Figs. 73
and 74, air pipes would be needed as shown, and in Fig. 75 an

Fig. 75-

emptying tap and a filling tube are required for the cistern
portion as well as an air pipe to the circulating service. The
filling tube to this latter pit should be of good size, so as to
allow of the free escape of air as the water poured in displaces
it, a 3-inch pipe might be used.

Three pipes are usually sufficient for these pits, but in
Fig. 74 the pipes are sometimes carried round the pit, and a
cross pipe used as in Fig. 76. Four-inch or 3-inch pipes are
used for these.

Examples of Hot-water Apparatus.

129

Fig. 76.

A very necessary feature in nearly all glasshouses whether
the hottest or the coolest, is what are known as evapo-
rating troughs, or trough pipes (see
fittings, p. 218). There are three
recognised forms of these : one being
as Fig. 77, in which the trough is cast
on and forms part of the pipe itself;
another is as Fig. 78, which is a cast
trough laid or resting upon an ordi-
nary pipe. Both of these require to
be filled by hand periodically. The
third sort is an open channel pipe
as Fig. 79; this, however, must be
fixed in a high position or it will over-
flow, and it is hardly worthy of mention,
as it is so rarely used.

There is no recognised rule as to -the quantity of these
pipes to be used in certain houses ; it is usual to put two or
three in all houses as they cost but little extra, and the
gardener need only use what he thinks proper, and usually

Fig. 77.

Fig. 78.

Fig. 79.

this is one of the details of a hot-water apparatus that has to
be carried out according to the gardener's wishes in the first
instance. The advantage of having a sufficient quantity is
that the houses may be used for different purposes at different

130 Warming Buildings by Hot Water.

times. At certain times of the year greater moisture is needed
than at others, and again there are times when the troughs are
used for evaporating others liquids than plain water. Perhaps
the movable trough Fig. 78 is most convenient, and occasion-
ally these are made in zinc for temporary purposes.

The object of these troughs is to provide a sufficient moist-
ness to the air or in technical language to "saturate" the
atmosphere. It is a well-known fact that the air at all
temperatures holds a certain amount of water in suspension,
but it is the least quantity with the lowest temperature,
and the greatest quantity with the highest ; air having an
increasing capacity for holding water in suspension as the
temperature rises. As an instance, we know that the morn-
ing dew and the freshness produced to vegetation by moisture
disappears gradually as the sun gains in power, and everything
has a different appearance at noon to what it had in the early
morning.

This result is entirely brought about by the transference
of moisture from the earth and vegetation to the air. We
have exactly the same result in a hothouse which is first
filled with air at a low temperature, which, as it becomes
heated, and its water-absorptive power increases, abstracts all
the moisture it can from the plants, &c., which will suffer in
proportion ; but by providing evaporating troughs the air is
saturated as the temperature increases. Indeed, it is easy to
over-saturate the air so as to have the peculiar dampness and
heat that are characteristic with luxuriant tropical vegetation.

In the hothouse and for ferns, moisture is in great request,
but in a grape-house the air must be dryer, especially at
certain times of the year. The gardener can generally judge
of these things to the best advantage, but in any case it will
be understood that evaporating troughs are provided to fulfil a
natural atmospheric law, and that without this precaution
plants would be robbed of moisture as well also as the earth
in which they grow, and their end would be quickly brought
about.

When we artificially heat a place, greenhouse, or residence,

Examples of Hot-water Apparatus. 1 3 1

we must artificially provide for the additional moisture that
the warmed air has increased capacity for, otherwise unnatural
results must ensue in a greenhouse as already described, but
in a place for habitation by the air becoming unhealthily dry,
a most undesirable state of things for bronchial troubles. This
subject will be more fully entered into when speaking of stoves
and appliances for warming a residence by first warming the
air. The necessity of supplying moisture to air as its
temperature is raised cannot be too strongly impressed upon
the reader, otherwise the air will help itself from any surround-
ing objects that have the least particle of moisture about them.
Natural heat is perpetually doing this ; it dries our roads, splits
and warps our woodwork, withers vegetation, and acts in a
thousand ways to this end, solely by reason of the sun causing
the air to become of a higher temperature, so that it has to rob
everything of moisture to satisfy as much as possible its
greater capacity for water.

In every illustration of hot-water heating apparatus devoted
to horticultural work, the pipes are shown running along the
walls hither and thither apparently without regard to situation
or as to how they may affect any roots (grape, peach, apricot,
roses, &c.) that have to be carried and supported against the
walls or elsewhere. It is impossible to suppose that the roots
can conveniently be disposed to suit the pipes, consequently,
recourse must be had to the gardener to settle this question
also. It is not necessary to entirely alter the plan of the pipes
on this account, but arrangements must be made that the
pipes do not come in anything like contact with the stems or
trunks of the plants.

Of course all this should be settled before commencing the
undertaking, as whether the work is done to estimate, or con-
tract, or otherwise, everything is planned out and arranged
beforehand ; at the same time it is possible for such a
detail as this to be overlooked. The average gardener will
permit of pipes coming as close as 6 inches to grape roots, if
it is necessary, and if the pipes are kept, say, 4 inches below
the lattice that supports pots, it will suffice ; but it is not usually

K 2

132 Warming Buildings by Hot Water.

permissible to have them closer than this. The general
plan is, as already shown, to have the roots on the wall side of
the house, and the pipes along the opposite side, but it fre-
quently happens that a vine root is outside the house and the
trunk trained to enter close to the ground, and then it becomes
necessary to dispose the pipes to clear this. If a quantity of
shrubs are growing close to the walls it is sometimes con-
venient to carry the pipes alongside the footway as at Fig. 69
(page 114).

( 133 )

CHAPTER VIII.

BOILERS.

Heating surface, direct and indirect Horizontal and vertical Different
resulting effects due to different conditions of the fuel Hood's
standard of heating surface areas and its application Boiler-makers'
lists, and the deduction necessary to be made from them Flue surface
and its value Action of flames and heated gases in flues
Fletcher's heat collectors ^Suggested new standard value of different
heating surfaces Small and large waterways Deposit, its effect and
removal Cast and wrought boilers Area of furnace bars
Hood's table, and necessary additions thereto Independent boilers
and fixing Gas boilers Coke boilers, the " Star," " Coil," " Finsbury,"
" Horse-shoe," " Ivanhoe," " Dome-top," " Independent terminal end
Saddle," " Challenge," and " Viaduct."

IT is only possible within the limits of this chapter to deal
with a representative selection of boilers, showing some of the
leading features, and illustrating the peculiarities of those that
have gained public favour and for which there is a fairly general
demand.

It is proposed to commence with the most simple forms,
viz., those which are heated by oil or a small Bunsen burner,
and from these to proceed by regular degrees to boilers
capable of fulfilling the greatest demand. There is no reason
why the small heaters, which combine boiler and radi-
ating pipes in the one article, should be neglected ; they are
of considerable use and fulfil a greatly felt want for amateur
greenhouse work, as they are capable not only of keeping the
frost out, but also of keeping the air at quite a mild tempera-
ture, and were they better known (for the few makers of these
articles keep in the background most strangely) they would
meet with a rather large demand and sale.

Before proceeding with the actual description of the various

134 Warming Buildings by Hot Water.

boilers it is necessary to refer to some of the special features
that a good boiler should have, and also to review Hood's
decisions in this direction. The first question to be con-
sidered is what qualities constitute a good boiler, that is an
efficient boiler, one that gives the best results for a given size
or space occupied, working under normal conditions and with-
out undue expenditure of fuel, labour, &c.

One would be led to think that this question had never yet
been satisfactorily answered judging by the number of differ-
ent boilers that have been designed from time to time. Even
now new forms are continually being introduced at fairly
regular periods, but it is evident that the old pattern " saddle "
boiler still retains favour as vast numbers of these are at this
moment being made and used about 10 times as many as
any other shape, and nearly every new one bears some resem-
blance to the saddle ; there -
Fi g- 8o - fore, for the study of what

constitutes a good boiler we
may take the saddle Fig. 80
as an example.

It can be readily under-
stood that the boiler surface
immediately facing the fire
or in direct contact with the
glowing fuel is at the

greatest advantage in heat absorption, particularly that part
of the boiler which is directly over the fire, as with a mass of
coal confined to a certain space as it is in a boiler, it will be
found that the greatest effect is by the heat that is radiated
from the top of the fire, assuming the fuel to be in an incan-
descent state. In any case it may be accepted as a recog-
nised fact and rule that the part of the boiler directly facing
or in contact with the fuel, absorbs heat at a much greater
speed than any flue surface, in a proportion that will be deter-
mined directly.

As a rule it is considered that the area of boiler surface
immediately over the fire is of greater value than that which

Boilers. 135

forms the sides or bounds the fire, in a proportion of about
three to two. Hood has fixed the ratio at this, and theo-
retically it may be accepted, though not strictly exact. It
is, however, desirable (to prevent an error being fallen into
here, for these results are only based upon the supposition
that the fire is in a similar state of combustion at sides and at
top), to adopt a more homely way of arriving at the con-
clusion. Let us suppose that we have a vessel of water which
has a side surface of the same area as the bottom (a cube for
instance) ; also let it be supposed that we have a fire in an
incandescent state with the top surface and the front surface
in an equally glowing state. Now if we boil the water by
placing the vessel on top, we shall get the result aimed at in
a much less time than if we put the side of the vessel against
the front of the fire. This is what it is intended to convey
when we read that the boiler surface over the fire is of a
greater value than that which bounds or comes opposite the
side of the fire. It may now be seen where the error may be
made, viz., in assuming the top of the fire to be always in a
glowing state.

Now if the gardener or attendant is skilled as a stoker (as
most of them are), and if he take the trouble to stoke the
fire regularly, by use of the dumb-plate, each charge of fuel is
coked and prepared before it is put upon the active part of
the fire, and its bright and glowing nature is little interfered
with. But this again is merely an assumed state of things, for
unless the apparatus is on a great scale necessitating the
almost constant employment of a fireman, there is very little
of the skilled stoking done, and neither is it expected nowa-
days, for in most of the new boilers introduced a feature is
made in economising time in stoking so that the fire can be
charged and need no attention for several hours thus giving
opportunity for other useful work to be done in the time that
might otherwise have been spent in stoking. It will also be
understood that during the night, with any description of
boiler, the fire has to be made up and cannot have constant
attention, and at night the greatest heat is needed.

136 Warming Buildings by Hot Water.

The object of this explanation is to show that only under
rather special and favourable circumstances is the top of the
fire in a bright and glowing condition, and to arrive at the
theoretical power of a boiler we must not be too ready to give
a much higher value to the surface over the fire as against the
surface at the sides of the fire, especially as the latter has
actual contact with the fuel, which the former has not. Again
referring to the kettle illustration we can see that if the front
of the fire was of red hot fuel and the top of the fire was black
with fuel newly put on, it is just possible that the kettle
placed in front would heat the more quickly. Under these
circumstances the boiler surface immediately around the fire,
whether at the sides or above, should be estimated to give
about equal results in the aggregate.

In every description of boiler, whether new or old, there is
one important feature that has to be studied in judging its
effectiveness, namely, whether it has every possible portion of
its surface area devoted to direct or primary heating, that is
surface coming directly opposite the fire, for should any
portion of this surface be sacrificed to make flues, unless the
flue surface so gained is three or four times as large as the
direct heating surface sacrificed, the result will be lessened
and not increased. Boilers have, and may have, flues by all
means, but flue surface being of so much less value than
direct heating surface (in a proportion that will be directly
investigated) it has never been found advantageous to lessen
the latter for the purpose of increasing the flue room.

This undoubtedly accounts for the favour that the saddle
boiler has so long enjoyed, its shape making it so capable of
benefiting by the heat, forming as it does an envelope to
the fire, and conducing to a freer circulation than we get
from a flat top. Hood points out the advantage gained
by the use of an old pattern boiler (which existed some years
ago but is no longer to be found) which much resembled a
large basin inverted over a fire, and having a flow pipe proceed-
ing from the apex. With this very excellent results were
obtained, but it could not conveniently have flues carried

Boilers.

137

around it and was not suited for any large purposes, but it
serves to illustrate the advantage of direct heating surface.

We have now, however, boilers that bound the fire on all
sides as the one just described did, but not necessarily circular,
and they have the advantage of being adapted for flues being

Fig. 81.

Fig. 82.

carried around them (so as to heat the outside surface as well

as the inside, as will be explained directly). One is the

saddle boiler but with water-way front and back ends, Fig. 8 1 ;

another is a circular boiler, Fig. 82,

which bears several names and will be

described in a later page. There are

also some other designs that fulfil this

object, in fact, makers are generally

alive to the importance of getting the

utmost direct heating surface and

making boilers to envelop the fire so

as to retain and benefit by the radiant

heat to the utmost extent. Flue surface

is nearly always- easy of attainment

and is of no very great value at the

best, except that part where the flame

has impact immediately it leaves the fire : the tail of the

flame and heated products after having travelled the length

of the boiler once, do but a very limited amount of good.

(See flame contact, p. 142).

138 Warming Buildings by Hot Water.

This now brings us to consider and discuss one of the
most important features in Hood's book, and which is
brought to the notice of every engineer when purchasing
boilers for hot water work : this is the question as to what
area of heating surface a boiler should have to render
a certain amount of service, or in other words, what amount
of pipe or radiating surface can be effectually worked from a
superficial (square) foot of boiler surface.

Hood, in his painstaking manner, went to great trouble
and apparently took note of many results before arriving
at and fixing his data, and to the best of every one's
judgment, he succeeded in getting accurate figures, but
unfortunately figures that could only be expected in results
under the most favoured conditions as to surroundings, con-
struction, quality of fuel, good stoking, external temperature,
&c. This is the more to be regretted as practically every
boiler maker has adopted his standard, with very unfortunate
results.

This standard which was set up, was that one square foot
of boiler surface subject to a direct heat was capable of heat-
ing 50 feet of 4-inch pipe, or if any flue or indirect heating
surface entered into the calculation then three times the
area was to be allowed, that is three square feet of indirect
heating surface was to be allowed for 50 feet of 4-inch pipe ;
this is the standard adopted by the majority of boiler makers,
but they are not free from fault in adopting it, as Hood
clearly points out the favourable circumstances, and strange
to say the boiler makers have overlooked an important
paragraph affecting this matter, in which Hood says, "A
very good proportion, suitable for nearly every purpose is to
allow about one foot of boiler surface (direct heating) to
about 40 superficial feet * of pipe or other radiating surface,
or about I -fifth more boiler surface than the preceding Table
states."

* The word " superficial " is correctly used as the circumference of a
4-inch pipe is so nearly 1 2 inches, that every foot in length of this sized
pipe may be called a superficial foot in this work.

Boilers. 139

This very clearly shows Hood's feeling in the matter,
viz., his disbelief in his original standard acting up to the
results given if worked under common conditions which
differ so greatly from the conditions that attend an experi-
ment. But, as before mentioned, this last paragraph and the
detail leading up to it have been quite overlooked by those
who have adopted his data and held him responsible for their
figures.

Of course the makers and users of boilers quickly became
aware of the unsatisfactory results that attended the adoption
of this standard when the articles in question were used in
the way that many boilers are used, which shows a great
desire to economise labour to the prejudice of good results,
consequently a method of obviating this difficulty had to be
discovered, and the general rule adopted is to adhere to
Hood's data, but with a brief preface as follows :

" The heating powers given in this price list of boilers
are based on Hood's standard work on hot-water heating,
viz., 50 feet of 4-inch pipe for each foot of direct heating
surface in boiler and one-third this quantity for indirect or
flue surface ; but for ordinary actual work the heating powers
in the list should be reduced 30 per cent, thus a boiler
estimated to heat 1000 feet should only be put to 700 feet to
do its work well and economically."

The standard list that this refers to is as follows :

Wrought Welded PLAIN SADDLE BOILERS, with from 2-inch to 3-inch
Waterways, according to size.

T w TT Approx. Heating Power,

4-inch Pipe.

24 x 12 x 12 300 feet.

30 x 14 x 14 425

36 x 16 x 16 600

42 x 18 x 18 800

48 X 21 X 21 1000

54 x 24 x 21 1300

60 X 24 X 21 I50O

This list is abbreviated for sake of space ; there are many
intermediate and some smaller sizes and of course there are

1 40 Warming Buildings by Hot Water.

many other lists that apply to other forms of boilers, but
all calculated results are based upon Hood's original
data, which require the deduction of fully 30 per cent, to
arrive at actual practical value under ordinary conditions.

Now in actual practice, especially if first cost is not of
great importance, it is desirable to make even a greater
deduction than this so as to permit of economy in stoking and
attention, and to provide for the advent of any unusual con-
dition, in weather, surroundings, or attention, that may occa-
sionally manifest itself. This greater deduction from the
standard list particularly applies to boilers that have a top
feeder as it is termed, like Fig. 83, which boiler is arranged

Fig. 83.

particularly for charging from the top and not from the
front, consequently the top or most valuable surface of the
fire is not usually in a bright state. This arrangement very
readily permits of putting a heavy charge of fuel in at
one time and thus less attention is required. Another ques-
tion to be discussed respecting the standard set up is as to
the value of flue surface, relative to that surface which comes
next to the fire and is heated direct.

Hood has fixed this at one-third, or three superficial
feet of flue surface, to give the same results as one foot of

Boilers. 141

direct heating surface. Here again there is a regrettable
difference between experimental and practical results, and
again is it necessary to hold the heating surface at a lower
value than the proportion set down. In the first place, we
have to consider that with the majority of boilers (the saddle
shape as an instance) we cannot get any flue surface beneath
the water space, the flues have necessarily to be carried along
the outer sides and across the top of the boiler. It has already
been shown what a much lower value vertical or side-heating
surface has, compared with horizontal flat surface with the
source of heat beneath it (the condition of the fire or flame
being equal in each case), so that when we consider what
value can be given to heating surface that is beneath the source
of heat, as it is when any flue is carried over the top of a
boiler, we shall find it is practically nil, of no use whatever,
or at least bearing only the most trifling comparison to the
direct heating surface that we get in the fire-box.

We have also to consider that flue surfaces quickly get
dirty when coal fuel is used, and even when nothing but coke
is burnt there is a deposit of dirt on flat surfaces, such as the
top of the boiler ; and whether the dirt be soot or of a dusty
nature, it requires but a thin coat to materially obstruct the
absorption of heat, as the dirt deposited in flues is always of
a low conductive power. This goes to lessen the value of
flue surface unless the flues were swept daily, which is not
done. Lastly, there is a phenomenon exhibited by flame
(supposing coal to form part or the whole of the fuel used),
which has been but little understood or noticed.

In the first place, any one having had experience with
flues of any description will have noticed that flames and other
heated products exhibit a strong disinclination to come in
contact with surfaces of any description ; and should the flues
be too large, the flame, &c., in its passage from the fire to the
chimney will not do so much useful work as it might do
otherwise. The objectionable feature in this is that the flame
gives off but little heat by radiation, and may be said to heat
by contact only, consequently the flues should be sufficiently

142 Warming Buildings by Hot Water.

small to bring about this result, at the same time not so small
as to become quickly stopped by soot, or to choke the draught
(passage of air, &c.). Flues to a furnace burning coke only
might be a trifle smaller than those connected with a coal
fire, but this will be dealt with in its proper place.

The next question, affecting the comparative value of flue
surface, is a somewhat peculiar one, involving the discussion of
a phenomenon that Thomas Fletcher, the well-known scientist
and gas engineer, treated in a paper read before the meeting
of the Gas Institute, London, June 9th, 1886, entitled, "Flame
Contact : a new departure in water heating." This is the
fact that flames under ordinary conditions do not come in
contact with a vessel containing water at all ; whether the
water is hot or cold, or whatever the vessel be made of, there
will exist a thin film of air or space between the flame and
the vessel so long as the vessel contains water, or, in other
words, so long as the metal of the vessel is prevented from
reaching a higher temperature than about 212. This film or
stratum of air does not exist when the flame is acting upon
some surface that is at a much higher temperature, it only
manifests itself when some cooling influence exists, as the
presence of water, which even at boiling-point seems to have
the repelling effect upon the flame as explained. This peculiar
action was fully explained by Fletcher in the paper referred
to, and it goes to show that, as applied to water heating, ordi-
nary flue surface is still further at a discount.

It is worthy of note that the remedy that Fletcher
suggests for this state of things takes the form of a suggestion
made by Hood, but the peculiarity is that
Fl S- 8 4- the two suggestions, although they would bring

about the same results, originate from different
ideas. Hood's proposition was the addition
of gills or projecting flanges outside and
beneath the boiler, as Fig. 84, with the view
of increasing the area of the heating surface to this extent.
From results obtained at that time it was decided that water
covering a certain area of boiler surface was capable of taking

Boilers. 143

up or absorbing heat 2 6 times as fast as it could be received
by the same given area from the fire, and the addition of these
flanges provided this extra heat-receiving surface without any
trouble being taken to increase the water-surface. This was
exceedingly successful with cast boilers, but its application
to wrought boilers has never been successfully carried out,
although it is worthy of serious attention from boiler-makers.*
It would not be necessary to adopt gills in particular ; any
mode of adding to the heat-collecting surface will do, but it
should consist of solid parts, for the reason that will be made
clear from Fletcher's investigations.

When Fletcher discovered that a metal surface at 212
or less practically repelled flame from contact with it (under
ordinary conditions), he set to work to devise a means
of obviating what in his practical mind was an objectionable
feature, and opposed to the best results. His experiments
showed him that a metal surface that could be raised to a
higher temperature readily received flame contact, so he
devised a vessel having a large number of solid projections
upon the bottom, as Fig. 85, and the differ-
ence in results in transference of heat from Fi S- 8 5-
the flame to the water was most remark-
able. In a small vessel of the ordinary
character with a flat bottom, 40 ounces of
water was boiled in three minutes fifty
seconds, whereas with a similar sized
vessel, but with the solid studs or rods on
the bottom, 40 ounces of water was boiled over the same
flame in one minute fifty seconds.! We see from this

* Corrugated boilers have been introduced for the generation of steam,
but these increase the water surface as well as the heat receiving surface,
which is not necessary. But with steam boilers the corrugations are an
element of safety, if undue pressure is exerted, as they give to the strain
instead of bursting.

t See ' Flame Contact, a new departure in water heating ; ' by Thos.
Fletcher, F.C.S., obtainable from T. Fletcher & Co., gas engineers, War-
rington.

144 Warming Buildings by Hot Water.

that solid projections (whether studs or plates) from a
boiler have the important advantage of adding to the heat-
receiving surface whether direct or from flame, as aimed at
by Hood, and secondly, they have the very important ad-
vantage of achieving the excellent results discovered by
Fletcher, of securing the actual, the utmost real benefit of
flame contact. This latter feature not only applies to flame
but to heated gases (products of combustion, &c.) also ; and
it is effectual when coke fuel is used, from which we get no
flame (except the small blue flames from carbonic monoxide).
It will be understood that the success lies in the fact that the
extremity of the rods or studs (which in this case were i Jin.
long) are too far removed from the water to have their tem-
perature kept down to anything like as low as 212 (after
having once become heated) ; yet by the rapid power of con-
duction possessed by iron or copper, they are all the time
transferring heat from their highly heated extremities to the
interior of the vessel.

This brings us to consider whether the flue or indirect
heating surface that we obtain with an ordinary saddle boiler
fixed in an ordinary way is of the value put to it, viz., three
superficial feet for 50 feet of 4-inch pipe ; and in the
writer's opinion it is not, far from it.

If a new standard could be introduced * it would be found
that for ordinary purposes, that is general horticultural and
other purposes, in which certain troublesome conditions occa-
sionally introduce themselves, but which in this case would

* This is somewhat improbable, as in the adoption of a new standard,
however necessary it may be, the makers of boilers would have their
interests prejudiced, as their goods would be apparently raised in price.
A saddle boiler for 500 feet of 4-inch pipe, now listed at 5/. Js. 6d.,
would, by the adoption of this proposed standard, be raised to about
8/. los. ; but, in the latter case, the 500 feet would represent the work that
could be actually performed by the boiler under the most ordinary and
common conditions with quite satisfactory results ; whereas at present,
when a boiler is required to heat 500 feet of pipe, the user has of neces-
sity to purchase one that the maker's list says will heat 750 feet, but in
reality will not.

Boilers.

'45

One square foot to 30
superficial feet of radiating
surface,

not require special consideration, this standard would be as
follows :

Suggested New Standard*

DIRECT HEATING
SURFACE. Whether the
boiler requires stoking in
the ordinary way, or is
arranged to take a charge
of coal to last several hours.

These figures are for an average square foot of heating
surface, that is to say, not necessarily that part which comes
nearest to the glowing mass of fuel, but to all the surface that
receives direct heat.

INDIRECT HEATING SURFACE. For primary flue surf ace,
that is, for flues that receive the flame and heat directly after it
leaves the fire-box, and which flues have, as a matter of course,
a greater value than secondary or return flues next in order :

If the flue is a flat or \ One square foot to 12
horizontal one, and the flame S superficial feet of radiating
passes beneath it . . . . j surface.

If the flue is a vertical | One square foot to 10
one, and the flame, &c,, acts V superficial feet of radiating
upon the one side of it . . J surface.

For secondary or return flue surface, that is, flues which
receive the flame or heat directly it leaves the primary flues
just alluded to :

If the flue is a flat or \ One square foot to 8
horizontal one, and the heat \ superficial feet of radiating
passes beneath it . . . . J surface.

If the flue is a vertical | One square foot to 6
one, and the heat acts upon ) superficial feet of radiating
the one side of it . . . . J surface.

* This standard could only be held to apply to boilers provided with a
correct area of furnace bars, as will be described directly.

146 Warming Buildings by Hot Water.

No allowance has been made for horizontal flues which
have the heat passing over them, such flues are usually as near
as possible valueless. The question of third and fourth flues
has also been ignored ; these are of value when circumstances
permit their use, and allowance could be made in proportion
to the foregoing figures ; but for these third and fourth flues,
and also the horizontal flues with heat passing over them, to
do any efficient duty, the draught must be stronger than is
usual in horticultural work of the ordinary character, as
chimneys of even moderate height are not permissible in the
gardens attached to a residence. In business establishments,
or with professional growers, the unsightliness of a taller
chimney is overlooked, a more powerful draught is at once
introduced, and in this case the flues just mentioned, although
still of the least value, add to the total efficiency, and all heat-
ing surfaces bear a greater value consequent upon the greater
consumption of fuel and heat evolved.

The standard just suggested is merely to take the place
of the impracticable one that is used by all boiler makers, for
boilers of the ordinary character and which constitute the
greatest number in demand. It is of course unreasonable to
still retain such fictitious figures, especially as even at this day
it leads to many unfortunate errors being made. Builders
and others who only occasionally use the articles, are not all
aware of the deduction to be made, and as the makers who
mention it in their catalogues only mention it once, it is easily
overlooked. Many makers would readily alter their figures,
but of course the alteration must be universal, or some would
appear to be charging very differently to others, higher or
lower, as the alteration had been made or not.

It may be held that the standard now suggested is too low,
but such is not the case ; it will only be found to give really
satisfactory results. It is quite of common occurrence for
boiler users to adopt half Hood's figures, that is, purchase
a 1000 feet boiler for 500 feet of 4- inch pipe, to ensure
efficiency with economy and to allow for possible irregularities
in stoking or conditions, and presuming first cost is not all-

Boilers.

important. If the standard just suggested errs in the least
degree (for it is quite impossible to arrive at exact figures,
conditions and other things never being twice alike) it errs
towards efficiency. If it were otherwise it would lead to per-
petual allowances being made for trifling circumstances.
Apart from this, every boiler user will endorse the writer's
opinion that a boiler should always be capable of over-doing
its work if pressed a little. A boiler that answers quickly to
any attention that is paid to the furnace gives the utmost
pleasure to the user. A boiler should be thoroughly effective
when the inclemency of the weather is inclined to tax its
capabilities, otherwise the work of months may be instantly
ruined or thrown back. Any boiler will heat a place in mild
weather, or it might suffice in the bitter weather if it had
constant attention, but no such risks should be run, especially
as the remedy is gained with two or three extra inches in the
length or width of the boiler.

The waterway in a boiler varies with its size the smallest
being 2-inch (none, however small, should be less than this),
the larger sizes being 3-inch and 4-inch; occasionally
boilers are made with still larger waterways, but these may
be considered rather as exceptions to the rule. There is no
gain in having an unusually large waterway, but the 4-inch
size is worthy of recommendation for the large and also for
moderate-sized boilers. In the first place, for a given sized
direct heating surface (the part which surrounds the fire, and
which is commonly called the inside) we get a greater indirect
or flue surface with a 4-inch than we do with a 3-inch
waterway, and by this means the efficiency of the boiler is
increased, although but very little. Some makers value the
heating properties of a 4-inch waterway boiler at one-
eighth more * than a 3-inch, but this is most unreasonable ;

* An aggregate eighth, that is, giving to the little extra flue surface
the credit of adding one-eighth to the total value of the boiler, whereas it
does not add one-eighth to the flue or indirect heating surface alone.

A letter upon this subject addressed to the writer by a hot-water
engineer of some note in London reads as follows : " The larger water-
way does certainly increase the power of the boiler, because of the

L 2

1 48 Warming Buildings by Hot Water.

the difference in actual results is hardly worth taking into
consideration in practice, unless the boiler was a really large
one. But of course boiler makers are quite justified in showing
some greater heating efficiency in their lists, as an increased
indirect surface does exist.

The chief advantage of a 4-inch waterway is its less
liability to become choked with deposit (sedimentary dirt,
foreign matter, or incrusted lime deposit) than with a narrower
size. This is worthy of consideration, as there is every necessity
to prepare for this trouble, for in the best constructed appa-
ratus in which care is used to exclude dirt, a sediment always
accumulates in time, and in an apparatus that is probably
tended by a boy who charges it with pond or ditch water, a
large amount of mud-like deposit quickly accumulates.

In every boiler there should be provision made for cleaning
out any deposit that may accumulate, whether it be dirt or
incrustation due to hard water. It is customary for this pur-
pose to put what are called mud holes at a low point in each
side of the boiler. These are merely fair-sized holes, drilled
and secured by a screw plug, and provision is made in the
brick setting for easy access and their removal when necessary.
Very commonly, and in fact usually, a pipe is brought from
these holes straight through the brickwork in front of the
boiler, these pipes being plugged at the ends ; this makes the
periodical flushing (to remove loose deposit or dirt) a simple
matter, as a cane can easily be pushed in to disturb the dirt.

The accumulation of incrusted lime deposit is a more serious
matter. This only occurs when what is known as " hard "
water is used ; this water containing lime in solution, which is
precipitated and adheres to surfaces most tenaciously when the
water is heated.* This is more difficult of removal than the

larger area of outside surface, but in my opinion not sufficiently to be
worth taking into calculation. ... I have found it very unsafe to take the
figures that appear in boilermakers' lists. ... I always deduct one-third
from the work values that appear in most catalogues."

* The heating process throws down the lime, and softens the water.
It is the same deposit or "fur" that we get in the tea-kettle when hard
water is used.

Boilers. 1 49

deposit of dirt it cannot be flushed out. This question is
more fully treated under hot- water supply (p. 333), and
the causes, remedies, &c., are fully dealt with there ; but it
should be mentioned here that, although the incrusted deposit
is the most difficult to contend with, it fortunately shows itself
very little in heating work, as firstly, it is the common practice
to use soft water (rain water from ditches or ponds, or collect-
ing tubs), which has no appreciable amount of lime in it ; and
secondly, if hard water is used it is not often changed, not
more than a gallon or so being evaporated in a week or
more (according to the size of apparatus), and as a given
quantity of water has only a certain (very small) amount of
lime in solution, the deposit is very trifling and does not
become noticeable for a very considerable time. It is only in
apparatuses that have the water continually drawn from them
(as in a domestic hot-water supply apparatus, or in a kettle)
that we get the thick incrusted accumulations.

If, however, a heating apparatus is fed by a cistern with a
ball valve, this usually means that the water is supplied from
a water company's mains. Should this water be hard, as is
nearly always the case in the southern half of England, the
incrusted lime deposit must be expected more or less quickly.
This will be governed by (i) the percentage of lime in the
water, (2) the quantity of water evaporated, and (3) whether
any water is drawn from the
apparatus for watering pur- Flg> 86 -

poses. This latter prac-
tice greatly aggravates the
trouble.

It has just been mentioned
that what are technically
termed " mudholes " should
be provided with every boiler,
these holes being situated one on each side, in front of
the boiler near the bottom, and generally having a pipe
screwed into each of them, as Fig. 86, so as to come through
the brickwork, which has to be erected in front of the boiler

150 Warming Buildings by Hot Water.

(unless it is one of an independent character). The object in
having these holes situated in the position shown is that any
accumulated deposit, whether hard or soft, can be removed from
the surface of the boiler where it is most likely to cause injury,
which is at the part pointed to by arrows in the illustration,
and where nearly every fracture takes place. This part can be
reached with a rod instrument inserted from the front, through
the holes referred to. If these bottom angles are kept clear the
boiler should do many years' good service. If the boiler is one
having a return pipe brought in upon one side only, it is the
other side the part of the boiler furthest from the return pipe
where the greatest soft deposit* will be found. Again refer-
ring to the question of large or small waterways to boilers,
it may be considered that for medium and large boilers
4-inch is a desirable size, and no gain will be effected by using
larger. An increased bulk of water is a disadvantage unless
it was desired to secure a store of water, in which case it
would be better to use a tank as a reservoir, f About the only
case in which a store of hot water is useful is when an equable
temperature is particularly needed with uncertain stoking.
In this case a tank of good size might be put in connection
with the apparatus, and provided it was well covered with
some poor conductor of heat, it would provide a storage of
hot water that would be circulated through the pipes and
give up heat for some little time after the fire was out. This
is a most unusual requirement, but nevertheless, it may
occasionally be resorted to, and is found useful in works of a
peculiar or special nature.

It will be found in the description of boilers that follows
this, that some are made of a very shallow shape, expressly
for use with what is called " shallow drainage," that is, situa-
tions where water is met with (when excavating for the boiler

* The term soft deposit is used as embracing all matters of a dirt-like
nature. The hard deposit (carbonate or sulphate) of lime is of a stony
character.

t A tank is sometimes of service when a pipe has to be carried below
the level of the boiler, as described on p. 81.

Boilers. 151

pit) very near to the surface of the ground, so that a deep
boiler pit is out of the question. Even those that may be con-
creted round, or lined with iron, cannot be kept free from
water if they are deeper than the point that the surface water
rises to, and the pits cannot under this circumstance be so
readily drained, as every pit should be, if possible, for various
reasons.

Boilers are made of cast iron, wrought iron, and copper.
The former and the latter are but seldom used, especially the
latter, by reason of its costliness. Cast iron is used to some
extent with small boilers, chiefly of the independent kind, and
is found fairly satisfactory, as they are but seldom subjected
to heavy usage. This material is also used in some kinds of
boilers of a larger size, as will be seen presently, and might
be used to a much greater extent if the right kind of admix-
ture of metal were used to produce a tough casting * which
would not only withstand rather violent handling, but would
last a long time without fracture from ordinary wear and
tear.

Wrought iron is the material nearly always used for boilers
'of moderate and large size, both of the independent and other
kinds. The plates are most commonly jointed by a weld,
this being cheaper than riveting, and is satisfactory in use ;

* To illustrate the difference in the natures of various brands of
cast iron, the writer once saw a cupola man in a foundry breaking pigs
of what is known as " white iron." A pig would break with one very
moderate blow of a sledge hammer, and not only break, but fly in four
or five pieces ; whereas a pig of superior iron, noted for its toughness and
softness, was subjected to about fifteen to twenty of the heaviest blows
with the same hammer, and, after all, had to be dropped across a block
of iron set edgeways before it came into two pieces ; then, instead of a
clean break, as is obtained with white iron, the break bore the appearance
of being torn asunder a never-failing sign of excellence of quality.
This foundry was devoted to the manufacture of cooking ranges, and the
castings, if struck at the edge, would burr over, instead of having a piece
fly off, as is expected, as a matter of course, with anything made of cast
iron. A casting of good quality should not break even if dropped a
moderate distance on to a stone surface, yet the average of castings met
with have to be handled like glass.

152 Warming Buildings by Hot Water.

but with large sizes, riveted joints are resorted to. All boiler-
makers' lists show two thicknesses of plate, viz., T V-mch and
flinch, the price differing about 20 per cent. The latter
thickness is always recommended, and if cost is not of primary
importance it should be used ; but it has often occurred to
the writer that if a boiler of each quality could work side by
side under exactly similar conditions it is doubtful whether the
f -inch would give 20 per cent, more service than the -^--inch.
We have to remember that many, in fact almost the majority
of boilers, do not fail from actual wear, but become fractured
by some accidental cause (accumulation of deposit, &c.), this
being obvious in a great measure by the fact that the fracture
nearly always takes place as shown in Fig. 86 (page 149).
But it is not intended to recommend the thinner plate, as in
good work it would be best to use the thicker quality, although
the advantage gained may not be quite proportionate.

There is another good reason for using f-inch plates, viz.
that when the apparatus is one that extends some distance
in a vertical direction, it necessarily brings a considerable
strain to bear upon the boiler which is at the lowest point.
However, this happens but rarely in horticultural works,
and the reader is therefore referred to p. 255, where the
subject is fully considered, as it need be, in heating of build-
ings and high places.

The last, but important subjects to be considered (before
dealing with the boilers themselves) are, the area of furnace
bars needed for certain boilers, and some general features that
should be studied in connection with furnace construction.
With some of the boilers that are described later, there will
be shown methods of setting them, particularly with the
ordinary saddle boiler which so greatly resembles many of the
more recent patterns, and is a guide in a great measure to the
treatment of these others, so far as setting is concerned ; but
with all of these there is a certain recognised rule to be
followed in deciding the size of the furnace bars. This rule
requires almost as much consideration in practice as that one
which governs the selection of the boiler itself.

Boilers.

153

Hood very correctly points out that the area of furnace
bars should bear a distinct and fixed relation to the area of
radiating surface, without any material consideration as to the
size of the boiler. This, however, must be allowed a little
latitude occasionally, as although with a certain area of fire-
bars we can consume only a certain quantity of coal in a
given time, whether the boiler be small or large (draught
and other conditions being equal), yet with a larger boiler
we should be getting better results generally, but under all
ordinary conditions a fixed rule can be adhered to with a
certainty of good results.* Occasionally a greater area is
desirable when a greater consumption of fuel is required, but
the special nature of the circumstances will decide what
proportionate extra area is needed.

If it is desired to get a greater heat by a proportionately
greater consumption of fuel, this is better effected by increas-
ing the area of furnace bars than by using ordinary sized
furnace bars and increasing the draught. Of course, a certain
amount of fuel will yield only a certain amount of heat, but
to economically utilise the heat evolved is, as just stated,
better effected by having a larger area of fire-bars with a
normal draught than a small set of bars with a stronger or
forced draught, for it has been a recognised rule always that
if the fuel can be had in a moderately thin layer spread over
a good surface, burning brightly (as it would do under such
conditions), better results will be attained than if we have to
confine the fuel to a smaller area in a mass, with a forced
draught. Another, though minor, objection to a forced draught
is that it necessitates more attention being given, and it also
causes undue wear and tear.

Hood's rule, or table, which is recognised and found
correct at the present day, is as follows.

* If in ordering a boiler the maker is asked to supply the fittings, he
will send a grating or furnace bars of a suitable area, together with the
furnace doors, dumb plate, &c., all of a correct size for the work the boiler
is supposed to do. This is a convenience if the purchaser desires to avoid
the trouble of calculating, &c.

154 Warming Buildings by Hot Water.

HOOD'S TABLE FOR CALCULATING THE AREA OF FURNACE BARS
NEEDED FOR CERTAIN LENGTHS OF PIPE.

Area of Bar,

75 square inches will supply 150 200 300

ioo 200 266 400

150 300 400 600

200 400 533 800

250 500 666 1000

300 600 800 1200

400 800 1066 1600

500 ICOO J333 2000

It will be seen that, although the table is extended to
eight lines, it really says that for all general purposes in which
small to fairly large sized boilers are used, it can be laid down
that each ioo feet of radiating surface should be allowed
50 square inches of furnace bars.

Now Hood's table can only be applied to plain saddle
boilers, as immediately we introduce a boiler with flue ways
or cross tubes, &c., in it, we increase its power with regard to
the radiating surface it can deal with, but we may not increase
the size of the furnace or the lower part of the boiler in the
least : and although in an instance like this the radiating
surface capable of being dealt with is greater than with a
plain saddle boiler, there is no need to increase the area of
furnace bars proportionately, or in fact, at all.

When Hood fixed his standard of 50 square inches of
fire-bars for ioo superficial feet of radiating surface, boilers
with check ends, chambered flues, cross tubes, &c., were little
known, or rather were accorded but little favour, but now
they have a considerable demand, particularly where space
is limited; and where we can get increased surface, particu-
larly direct heating surface, and increased results for a given
amount of fuel, without increased size, it is, generally speaking,
a desirable end attained.

In practice it is found that, adopting Hood's calculation
(which is strictly practical) for saddle boilers, a list, such as
the following, gives accurate results under ordinary conditions,
and with an ordinary draught.

Boilers. 155

The areas mentioned in the following table include the
bars and the spaces between the bars. The table may be
varied to suit special requirements, and no noticeable trouble
is experienced if under ordinary circumstances the area is
increased a little beyond the proportions given, but it is by
no means ever desirable to decrease the areas suggested. An
increased area with a low draught is better than the reverse.
For every 100 superficial feet of radiating surface allow :

TABLE SHOWING THE AREA OF FURNACE BARS FOR VARIOUS
KINDS OF BOILERS AT PRESENT IN USE.

Square inches.

With a plain boiler 50

saddle boiler having one check or waterway

end 45

two waterway ends (front

and back) .. .. 40

a tubular flue (as Fig. 125) 40

two tubular flues . . . . 38

With saddle boilers such as Figs. 127 and 128, which

have check ends and tubular flues 35

If a boiler is fitted with a cross tube (as Fig. 102) the
area of furnace bars can be reduced below the
above figures for every 100 feet of radiating sur-
face 5 to 10

Keith's boilers are worked with an average of about
20 square inches of furnace bars per 100 feet of
radiating surface. This low allowance is sufficient,
the direct heating surface being so extensive
within a small area.

From this table it will be seen that a plain saddle boiler,
estimated to heat say 800 superficial feet of radiating surface,
should have furnace bars of an area of 400 inches ; but if this
boiler were fitted with an oval cross (waterway) tube, it would
be capable of dealing with 1000 feet of radiating surface, but
the area of fire-bars need not exceed the measurements above
given.

In dealing with the following representative variety of
boilers, no particular distinction will be made between those
used for horticultural works and those that may be better
adapted for heating buildings. Up to the present we have

156 Warming Buildings by Hot Water.

almost exclusively dealt with horticultural undertakings, but
there is no need to have more than the one general description
of boilers, and therefore this chapter must be made to apply to
the other articles upon low-pressure heating which follow.

INDEPENDENT BOILERS.

These boilers, as the name signifies, are constructed in
such a manner as to be quite independent of any construc-
tional work in fixing. Assuming that they are stood upon a
non-inflammable floor or base, there is no need of any brick
or mason's work to make them complete. The connection
with the chimney is effected by a pipe, and the furnace is
made and enclosed in iron, and forms a lower part to the
boiler itself.

These boilers are rarely used for large undertakings, as
their power is somewhat limited, and they cannot be used
so economically as those that are arranged for a brickwork
setting ; but for small and moderate undertakings their use-
fulness cannot be over-estimated.

Perhaps the chief drawback to the efficiency of these
boilers is the inability to make use of the outside shell as
heating surface (what has been termed the flue or indirect
heating surface in brick-set boilers). And unless some pre-
cautions are taken, the outer surface will bring about a con-
siderable loss of heat by radiation, an impossible thing when
a boiler is surrounded by brickwork, or with flues containing
flame or heated gases.

It is very desirable, and, properly speaking, necessary to
coat or surround independent boilers with some poor con-
ductor of heat, otherwise the practical as well as the theoretical
value of the boiler will be unreliable, varying in results with
the heat or coldness of its position and surroundings. There
are very many materials that can be utilised for the con-
servation of heat as applied to boilers, but not all are very
easy of application. Slag wool or silicate cotton, for instance,
is a material most highly suited for surrounding heated bodies,
even those that attain a temperature that would ignite any-

Boilers. 157

thing like hair felt, as it is non-inflammable, and is as near
as possible a non-conductor of heat ; but as it is a wool-like
substance, it would require to be encased round the boiler,
and this is not convenient. Asbestos is another material of
a similar character ; * but there are now several patented
compositions in which, no doubt, silicate cotton and asbestos
represent the chief ingredients, and these are fairly easy of
application, the chief care commonly being to see that the
first coat is made to adhere to the metal, this usually being
effected by well rubbing it on.

For an application of this material to be thoroughly effec-
tive it should be put on sufficiently thick to wholly prevent loss
of heat. It usually requires a layer or coating of I J inches
to 2 inches thickness to do this (with the boilers now being
spoken of), and if when the boiler is full of hot water the hand
is applied to this coating and no heat is felt, it is sufficient
indication that no waste of heat is occurring in this direction.
If space and appearance are of no object, brickwork built
closely round the boiler would answer admirably ; but this is
a clumsy method, and defeats the object sought in having the
boiler of an independent character. Of course, if the boiler
or any portion of it was situated in the green-house itself,
then there would be no occasion to cover it where the heat
radiated was useful in effect and not wasted.

As before mentioned, it is intended to commence with the
smallest form of boiler, one which has the radiating surface
made in connection with it, as, although these little appliances
may be esteemed trivial to engineers of great enterprises, they
are found particularly valuable in amateur works and for the
small glass houses that are often attached to residences. If
it were not for these useful little devices it would necessarily
become expensive to heat the place, as an independent boiler,
of one of the kinds presently described, and a system of pipes
would be necessary, as any system of heating by oil stoves is
usually found unsatisfactory from several causes.

* Both these articles can be had in sheets and slabs, &c., but then
they are not so easily applied to boilers as a cement compound.

158 Warming Binldings by Hot Water.

Fig. 87.

Fig. 87 * shows an apparatus where the boiler is made ot
sheet iron or copper, and the whole outer surface japanned.
This is arranged to burn oil or gas, the latter for preference.

For gas burning they are
made in various sizes, the
largest being capable of heat-
ing 100 feet of 3-inch pipe.
In the small sizes they fulfil
a decided want, as they are so
readily fixed, and the price
is particularly reasonable, the
smallest costing but 2Os., in-
clusive of boiler and case,
atmospheric burner, 10 feet
of 2-inch pipe, feeder stand,

a purifier to fit in the flue outlet, and indiarubber rings to joint
the pipes, &c. ; an extensive list of appliances for such a small
sum. These boilers can also be had fitted with a flow and
return on each side, and so be situated in the centre of the
work if desired.

The maker of these appliances introduces a purifier to the
gas boilers and heating appliances of small size, this appliance
being a metal case containing charcoal, through which the
products of combustion have to pass. This material is pro-
vided to intercept the sulphurous acid which is so particularly
hurtful to plant life. This and other details will be more fully
discussed when finishing the subject of gas-heated boilers

(P. 163).

* It is proposed to give the names of the makers of the different boilers
and appliances that will be illustrated ; firstly, for the convenience of those
readers who may wish to use the particular appliances referred to ; and,
secondly, in recognition of the loan of the blocks from which the illustra-
tions are printed.

The above illustration is from the catalogue of Messrs. Charles Toope
& Co., of Stepney Square, London. Mr. Toope, in addition to being a
manufacturer of appliances, is an ardent amateur grower, and takes
great pride in his collection of orchids, especially as they are grown in
Stepney.

Boilers.

'59

Fig. 88* shows a very original little appliance for window
conservatories, its neatness is admirable, yet it is quite com-
plete, with boiler, gas burner, filling tube, and a flow and
return pipe carried all round the outer boundary of the en-
closure. Of course, the gas burner would require to be left

alight night and day in severe weather, and attention must
needs be given to the filling tube ; in fact, the same details
are present that we obtain in a larger apparatus, but it very
probably would not fall to a gardener's lot to attend to this
one. The attention needed in replenishing would not be at
all objectionable, provided the gas flame was properly regu-
lated and no unnecessary evaporation took place ; a candle
flame, if it were smokeless, would almost suffice.

Fig. 89! represents a most ingenious form of gas boiler,
embodying in a practical form the suggestions made in Mr.
Thomas Fletcher's paper upon " Flame Contact."

Mr. Fletcher, in his paper read before the Gas Institute,
stated that flame, whether from gas or coal (practically one

* This illustration also is from Messrs. Toope's list.

f From the catalogue of Messrs. T. Fletcher & Co., of Warrington.

1 60 Warming Buildings by Hot Water.

and the same thing), had no actual contact with a vessel
containing water at or below 212 (boiling point), and he
adduced in evidence several experiments to convincingly prove
this. His suggested remedy, which is very
practical, appears in the appliance just
illustrated in the form of a number of solid
studs or rods projecting from the heating
surface, these projections acting as heat
collectors and conductors. He went on to
say that flame readily had contact with
bodies at a higher temperature than boil-
ing water (with increased effect) com-
mencing at about 400, and this takes place
with the projecting rods on the boiler, the
heat being transferred from their extremities
to the water by the high conductive power
of the metal of which the rods are composed (copper). It
might be inferred that the projections simply act as increased
heating surface, and the same results would be obtained if
the rods were hollow,* but this is not the case, as he showed
by experiment and subsequent calculation. Another peculiar
feature with the solid rods is that they present fully twice as
much heat-receiving surface to the fire as there is water sur-
face, yet they are at no disadvantage, as a given surface
of water is capable of absorbing heat at 2-5 times the rate
that the same surface of metal (iron) is capable of receiving
and transferring it t

* If these projections were hollow, they would fail quickly with hard
water, by becoming solid with incrusted deposit.

Mr. Fletcher has set a limit to the length of these studs, as beyond a
certain point they receive more heat than the water can as quickly absorb,
and the extremities then perish.

t A boiler tube has just been introduced which is a practical applica-
tion of this, it being a tube of ordinary length and diameter, but having a

series of longitudinal ribs or gills within it thus ^ > which do not

interfere with the flue brush, and are considered to give fully 30 per cent,
better results than a plain tube.

Boilers.

161

Fig. 90.

The effectiveness of this principle is demonstrated with
the boiler now referred to (Fig. 89), as a small size, measur-
ing but 6 inches in diameter and 5 inches in height, is
sufficient to heat 40 feet of 2-inch iron pipe (practical
quantity) without undue consumption of gas or specially
favourable conditions. It requires no support to itself, as
the rigidity of the pipes is sufficient for such a light con-
trivance, but a boiler of this kind requires
to be fixed outside the greenhouse, as
will be explained directly.

Fig. 90* illustrates another boiler
having Fletcher's principle applied to
it, but differing considerably from the
last so far as shape is concerned. This
boiler is made of cast iron, and one par-
ticular feature is that its construction is
such that it can be used for supplying
hot water for draw-off purposes, not-
withstanding that a hard deposit may
accumulate, for a lid is provided, easy
of removal, that gives access to all parts

where the accumulation may occur. Provision is also made
for easy removal of soot, should the light be attended to
carelessly, causing soot to be formed and deposited.

Hood as early as 1828 adopted the plan of having a great number
of solid protuberances on the heating surfaces of boilers, first, in the form
of rods or pins, and subsequently in the form of continuous bars or ribs ;
and a Mr. Sylvester afterwards in 1835, an d a Mr. Williams in 1841, both
patented other adaptations of this idea. In effect Hood found the plan
very successful, but, apparently, no part of the resulting gain was in any
way credited to the fact that the flame readily came in contact with the
extremities of these projections ; whereas it would not do so with the plain
boiler surface. No mention of this fact is made by Hood, so doubtless
it escaped observation ; but Mr. Keith found a greater practical value
in this improvement, and more recently adapted it again with success ;
but he found care was needed in the use of these projecting parts, as they
are apt to collect soot, &c., and thus defeat their usefulness.

* Also from Messrs. Fletcher's catalogue.

1 62 Warming Buildings by Hot Water.

Fig. 91.

Fig. 91* illustrates another form of gas boiler upon an
ingenious principle of forming the construction in sections.
This principle is adopted by Mr. Keith in nearly all the
boilers that he makes.t A particular gain is effected by this

arrangement in various ways, the chief
being that by making these boilers
in parts of moderate bulk a great com-
plexity of form can be more readily
given them (for they are of cast iron),
so as to give the greatest possible
heating surface by tubes, convolutions,
&c., which could not be nearly so
well effected if the boiler was con-
structed any other way. In the
boilers of large size (for coal burning)
this arrangement simplifies the diffi-
culties of transport, fixing, &c., and it
enables a very great variety of sizes
or powers, to be readily supplied (but
this latter is chiefly to the maker's

advantage). It will be necessary, however, to again refer to
this style of boiler later in the chapter, and fuller particulars
can then be given, as most details apply to those boilers con-
structed for coal and coke burning. The particular boiler
now being referred to (Fig. 91) is but 13 inches square,
but varies from 15 to 28 inches in height, depending upon
the number of sections used.

Gas boilers are not made to heat more than about
100 feet of 4-inch pipe (200 feet of 2-inch), but if desired,
no doubt they could be made larger to order ; but if a
larger quantity of pipe than the above had to be heated
by gas, it would be better to have a group of the 100
feet boilers, a battery so to speak, connected together,

* From the catalogue of Mr. James Keith, 57, Holborn Viaduct,
London.

f Mr. Keith also uses heat collecting studs and fins in his boilers, and has
done so for many years, having included them in one of his patents in 1875.

Boilers. 1 63

than one of an unusual size.* They could then be used
one or more at the time as desired. Every gas boiler,
whether small or large, should, properly speaking, be fixed
outside the greenhouse. Under some circumstances, and
where they receive attention and care, they do well inside,
but this should be considered merely an exception to the
rule, and by no means be regarded as a precedent even by
those who have fixed them inside successfully. Even when
so fixed, the burnt gases, as they are called, the products of
combustion, must be carried outside except in the very small
sizes. Small stoves are sometimes fixed inside, and discharge
their products there without appreciable ill effect, provided a
means is adopted of arresting the sulphur fumes (sulphurous
acid SO 2 ) that are always given off from gas stoves, and which
are so particularly hurtful to plant life, even in small volume
such as we get from a single gas-burner for instance, if the
area be limited. The question as to the different properties
of the products of combustion from gas-burners will well bear
a short explanation, as new gas stoves for various purposes
are being introduced every season, and many of them are
devoted to greenhouse and conservatory work.

The products derived by the combustion of carburetted
hydrogen (coal gas) burnt from a Bunsen or atmospheric burner,
which is almost exclusively used in heating work, consist of
carbonic acid (CO 2 ) and water (H a O),f and some other gaseous
matters which are the results of impurities which cannot
wholly be eliminated in the manufacture. These impurities,
with one exception, are either harmless or in such small
quantity as to be of no consequence. The exception is sul-
phurous acid, which is brought about by the combustion of a
small percentage of sulphur which is always carried over
with the gas in the manufacture, and at present cannot

* The chief reason why larger gas boilers are not made is that the
demand would be so limited ; for if any large quantity of pipe had to be
heated, a gas boiler could not do it nearly so economically as a boiler
heated by coke.

t Of course another, and the chief result of combustion, is heat. See
Combustion.

M 2

1 64 Warming Buildings by Hot Water.

wholly be disposed of, although every effort is made to effect
its removal.

It is the sulphurous acid and carbonic acid gases that are
the objectionable elements in the products, but the former
is most hurtful to foliage. It has been mentioned that small
stoves may discharge their products into the greenhouse
without any noticeable effect, provided the former of these
two substances is arrested. This is because carbonic acid in
limited quantity is non-injurious to plants, it being their food,*
but even this latter substance must not be present in any
volume, as apart from its effect upon plants, it would then
become hurtful to human life, causing asphyxiation. With
small gas stoves the removal of the sulphurous acid is
generally done by taking advantage of the great affinity this
substance has for water. One of the products of combustion
is water, as just explained, and if this water of combustion is
condensed by being brought into contact with a cooling
surface before it escapes, it will be found to have collected
the sulphur with it, and the carbonic acid will go free, in-
odorous and tasteless, and not so observable as when it
carried the unpleasant odour of sulphur with it. This has
led a good many makers of gas stoves to perpetrate what
looks greatly like an imposition upon the public, as there is
a form of stove now made called a " condensing " stove,
which acts in the manner just explained, the water of com-
bustion being condensed! by having to pass through two
cast-iron tubular columns. A maker's list before the writer
distinctly states that "all the products of combustion are
condensed." We must charitably attribute this assertion to
ignorance, as Nature lends her aid to the deception by making
the carbonic acid quite unnoticeable to the average person

* Plant life absorbs, and is nourished by carbonic acid (but in daylight
only). The carbon is taken up, and goes to make living material, and the
oxygen is set free.

t Approximately it will be found that the greater part of a pint of
water can be brought down from every 30 feet of gas burnt, the quantity
varying, however, with the area or coolness of the condensing surface.
This water has a very unpleasant smell, and acid properties.

Boilers. 165

after the sulphur is removed. It is fortunate this style of
stove cannot well be made in large size, for the volume of
acid gas then given off would speedily be dangerous in a
small or close apartment.

There are two chief objections to having a gas boiler in
the greenhouse. One is the possibility of the gas escaping (by
accident, carelessness, or other cause) unburnt,* this being
firstly an element of danger by explosion, and it is just
about as injurious to plants as the sulphurous acid just spoken
of. The second objection is the liability of the products of
combustion being discharged into the house notwithstanding
the flue provided to carry them outside.

There is a notion, much too prevalent, that a piece of pipe
taken from the stove through the wall, constitutes a sufficient
flue for a gas stove, but nothing could be more incorrect, a
flue to a gas stove must be erected and carried out in every detaL
tJie same as a flue for a coal stove, but because the ill action of
the flue cannot be very well noticed with a gas stove as it can
when there is smoke, these flues are commonly put up upon
some hypothesis of the workmen engaged (and their ideas
are extraordinary sometimes)! and the consequence is that
on many days (depending upon the direction of the wind
usually) the products will not pass out of the flue-way at all,
but insist upon coming into the house. The question of flues
or chimneys will receive proper treatment in a later chapter
(see Chimneys), and it will therefore suffice to mention here
that the flue from a gas stove should rise above the house top,

* For this reason, the flue pipe from a gas stove should never be
carried into the brick chimney of a house, as an escape of gas from
the stove might bring about serious results.

t An exceedingly common idea entertained by many, even well-
informed people, is that if a coal stove or grate is rendered useless by
reason of the chimney having a defective draught, a gas stove can be
successfully substituted, the supposition being that the gaseous products
from the latter will pass up the chimney in no way interfered with by the
bad draught, although exactly similar products from a coal fire, but carrying
a little soot with them, fail to do so. No notion could be more incorrect
in fact, it borders upon absurdity ; and, although not entertained by
specialists, it is very prevalent amongst workpeople.

1 66 Warming Buildings by Hot Water.

and in some cases the addition of a conical cap is desirable or
necessary.

If the boiler is fixed outside the house it is still necessary
to carry the flue up to a sufficient height, as, although the
escape of combustion products will not then materially matter,
the down-draught will interfere seriously with the proper
working of the burner (usually by blowing the light out),
sufficiently so in all probability to render the apparatus useless,
and it must not be forgotten that in an iron flue a deal of
condensation will most probably take place, depending upon
the situation, and some provision must be made for the
disposal of the constant stream of water that will be trickling
down the flue if the products of combustion become sufficiently
cooled to bring about this result.

When a gas boiler is fixed outside the house it becomes
necessary to surround it with a box-like structure, a little
house, to protect it from the elements, particularly from strong
winds, which will be found to interfere seriously with its steady
working unless some method is adopted to guard against the
trouble. This enclosure must not be anything like air-tight,
as the burners, like a coke furnace, must have a copious supply
of air to effect combustion, and in addition to this, as the
burner is sure to be of the atmospheric type, a free supply of
air must have admission to this also, otherwise the peculiar
character of the burner will be destroyed, and the worst results
ensue. A grating, or strip of perforated metal, is all that is
needed to ensure the necessary supply of air, but let this be of
fair size, and insert it in the side of the structure that is least
exposed to the weather.

A very necessary precaution in the use of a gas boiler,
particularly with one that is enclosed, is never to turn on the
gas until the light is ready to be applied, and before the light
is applied it is a wise precaution to open wide the door of the
enclosure, so that any possible collection of gas may be
dispersed. If a burner is blown out by the wind there is
instantly a source of danger, by the escape of unconsumed gas
that takes place.

Boilers.

We can now turn to the consideration of independent
boilers that are used with coke fuel.* These outrival gas
boilers in variety, also in power, and although they may need
a little more attention in stoking and occasion a little trouble
by dirt, they are considered more reliable, and there is less
trouble in other ways. Very many of them are now made
that will admit of economy in attention by taking a charge of
fuel sufficient for many hours (depending, however, upon the
way the flue damper is used).

Fig. 92.

Fig- 93-

Figs. 92 and 93 f illustrate the least powerful and least
expensive of these, yet having all the essential features and
conveniences of the larger ones. These are usually known as

* Occasionally 'ordinary and small coal is burnt in independent boilers,
but it is objectionable in many ways, and should never be used if coke can
be obtained (this is not always possible, if the boiler is in some remote
country place, and no gas works within very many miles). The chief
advantage with coke is its adaptability for charging purposes ; for as fast
as the lower part of the charge burns away some more falls to replace it.
and this could not be relied upon with coal, as it fuses, and cakes into a
mass.

t From the catalogue of Messrs. Hartley & Sugden, Halifax (England).

1 68 Warming Buildings by Hot Water.

" star " boilers, but different makers give them different names
to suit their own purposes, for this pattern is not confined
exclusively to one manufacturer, it can be seen in nearly every
boiler maker's list that may be taken up. Both have top
feeders, that a good charge of fuel may be put in at once, but
Fig. 93 is particularly adapted for this, as the extended portion
on top is provided expressly to take a greater quantity of
fuel, this fuel gradually falling and coming within the area of
combustion as that nearest the furnace bars is consumed.
This advantage is greatly heightened by having the boilers,
and also this extended fuel chamber, slightly conical in shape,
as this prevents all liability of the fuel " bridging " itself, that
is refusing to fall, and added to this the conical shape causes
the sides to slightly overhang the fire, and the more this can
be done, the better the results.

The writer would much like to see a boiler of this class or
the " dome top " (presently to be mentioned) provided in every
private residence of fair size to furnish hot water for domestic
purposes, instead of the customary " high-pressure " boiler
that is fixed in the kitchen range. The results with an inde-
pendent boiler are so much more regular, not depending upon
the cooking (which regulates the attention to the fire), and the
charge of fuel spoken of would keep the water hot night and
day, and there would be plenty in the early morning, when
there usually is none. In many cases there would be an
actual saving in fuel, for it is really astonishing how much
more quickly a cooking range acts when it has no boiler in
actual contact with the fire, and how very economical in fuel
it at once becomes (see ' Hot Water/ p. 350).

The boilers just referred to (Figs. 92 and 93) are made to
heat from 1 50 to 700 feet of 2-inch pipe (theoretical quantity).
Both are made in exactly the same sizes, the disparity in the
illustrations is rather misleading. They are made of cast-iron,
and the pipe-sockets and flue nozzle can be had on right, left,
or at back as desired.

Fig. 94* represents what is known as a coil boiler, con-
* From the catalogue of Messrs. Hartley & Sugden, Halifax (England).

Boilers.

169

sisting of an outer iron case, with the usual furnace fittings,

&c., but instead of having what we recognise as a boiler it has

a coil of pipe placed so that the fire acts strongly upon it, as

shown in the illustration, which exposes

the interior of the boiler. This boiler is Fi S- 94-

also of small size, to heat from 100 to

450 feet of 2-inch pipe, but it has all the

necessary fittings complete, and it will

take sufficient fuel to last all night without

attention.

A coil, under some circumstances, may
be considered the most powerful form of
boiler (for the space it occupies) ever in-
troduced, as it is wholly direct heating
surface, and is also wholly in contact with
the glowing mass of fuel, but there are
objections to its use (which objections are
greatly obviated by using a large-sized
pipe, as will be referred to when treating
brick-set boilers).

Perhaps the great objection is in the

smallness of the pipe, causing a stoppage and subsequent
fracture by the accumulated dirt, which is difficult of removal,
and this precludes its use in anything like a complex form.*
There is no objection to a coil of this description upon a small
scale, as the evaporation and consequent replenishing of the
water supply is not great, and there should be a proportionate
decrease of the dirt that finds its way into the pipes. It is a
common and very convenient arrangement to put a coil of
two or three pipes into an ordinary grate for the purpose of
heating a radiator in another room of a residence, as is ex-
plained on p, 281.

Figs. 95 and 96 1 show a description of boiler commanding

* In heating apparatuses upon the high-pressure system, large coils of
small pipe are invariably used, but in this case the apparatus is sealed,
and all dirt matter is thus excluded.

t The " Finsbury boiler," from the catalogue of Messrs. Lumby, Son,
& Wood, Limited, of Halifax (England).

1 70 Warming Buildings by Hot Water.

a large sale, and which has received much favour since its first
introduction a few years ago. It was first introduced under
the name of the " Loughborough " boiler, as it originated in

Fig. 95. Fig. 96.

that place, and it fulfils a decided want. Its peculiarity con-
sists in its being adapted for building in the thickness of a
wall (see p. 98), so that all the stoking and feeding doors
are practically away from the greenhouse, yet the pipe con-
nections are inside, and every inch of pipe does useful work,
thus saving the cost of providing connecting pipes between
the boiler and the radiating pipes (so commonly necessary
with independent boilers, which cannot always be fixed near
to the house) and also the loss of heat that takes place from
these connecting pipes unless they are well protected.

It will be noticed that there Is an arrangement inside
which prevents the flame and heated gases taking a short cut
up the front of the boiler and out of the flue way, and they
are instead compelled to come in contact with the back and
sides and impinge against the top, and thus give their greatest
effectiveness. In the writer's opinion the waterway front is not
of value proportionate to its cost, as this part is openly exposed
to all weathers, and the water in contact at this point experi-
ences a great cooling influence which must materially prejudice

Boilers.

171

the efficiency of the other heating surfaces. These boilers are
made to heat from 300 to 1200 feet of 2-inch pipe, and the
smoke nozzle (which is fitted with a damper) can be placed
on right or left side of the front as required.

Fig. 97* is a boiler similar in character to the one just
described, being suited for fixing in the thickness of a wall,

Fig. 97.

but it has one or two improvements that are desirable addi-
tions to a stove of this description. This is called by the
makers " The Horse-shoe boiler " as the plan of the boiler
portion is of this shape extending round the back and the
sides in a semicircular form. There is no waterway across
the front, and as just mentioned, none is needed ; but in this
boiler there is a peculiar arrangement for the inflowing air to
pass down just inside the front as illustrated, so that it becomes
highly heated before it enters the fire, a hot blast in fact, which
* From the catalogue of Messrs. Kinnell & Co., Southwark, London.

172 Warming Buildings by Hot Water.

produces economical results. A further feature is what the
makers call a revolving bottom grating. This, however, does
not revolve, but can be made to oscillate or rock, so as to
shake out the ash that accumulates and chokes the draught.
A further feature peculiar to this boiler is an automatic or
self-regulati'ng air-inlet, shown as a flap in the illustration,
just below the feeding door. This flap acts upon the principle
of Dr. Arnott's ventilator in the fact that it can be set so as
to adjust itself to the draught, a feeble draught leaving it full
open, a strong draught drawing it partially close. This im-
provement is worthy of commendation, as it is in reality a
self-acting damper, a thing very much desired, but, to the
best of the writer's belief, not yet made in a perfect form, a
form that will prove itself efficient at all times under all
conditions. If the one now in question acts perfectly, the
maker (or inventor) is deserving of the highest praise.

It will be readily understood that a damper does not of
necessity have to be in the flue, as a provision for regulating
the inflow of air to a fire, checks or accelerates combustion
just as well as a provision for regulating the draught up a
chimney ; in both cases the passage of air through the fire is
controlled equally, and this controls the speed of combustion.
A self-acting damper evinces its utility particularly when the
draught in a chimney is variable (as is frequently the case, for
the wind and weather will commonly bring about this effect),
as it will then accommodate itself to the varied conditions,
and the draught or passage of air through the fire will remain
regular.

Another good feature in this boiler is that the waterway
is continued below the fire-bars. This is a feature that can
be had with almost any wrought iron independent boiler, if so
ordered ; it could also, with some extra trouble, be arranged
with brick-set boilers. It incurs a little extra expense, but is
even better if the waterway is also brought right beneath the
ashpit as in Fig. 98.* The advantage gained is that accumu-
lations of sedimentary matter (dirt) which always settle at
* From Messrs. Hartley and Sugden's catalogue.

Boilers.

Fig. 98.

the lowest point, are taken below the fire, so that, however
much it may collect at this point, its effect is nil, for it is only
when the deposit is successful in keeping the water away from
the boiler plate, against which the
fire acts> that harm ensues, or a frac-
ture occurs. Were there a return
pipe entering the boiler at the
bottom just above the level of the
fire-bars, this pipe would more
readily get stopped with dirt if the
boiler terminated at the fire-bars,
than it would if the boiler were
continued below.

The desirability of having the
waterway right across the bottom
beneath the ashpit, as just illus-
trated, consists in that it permits the
whole accumulated matter to be
removed from one mudhole (if a
good-sized one is put) as the raking

instrument when inserted will reach all around the lower part,
as can readily be understood.* This advantage applies chiefly
to boilers that are circular in form, as most independent boilers
are, for it can be seen how difficult it is to clear out the deposit
from the cylindrical portion of the waterway, unless some five
or six manholes are provided, and then it cannot be done
so well ; the waterway bottom forms a sort of catch-pit or
settling bed for sedimentary matter.

With hard deposit (" fur ") the waterway bottom has a
beneficial effect, but of a different character, in this way.
When this matter is precipitated it generally adheres to the
surface it is deposited upon, particularly if this surface is at a
high temperature. Now the surfaces bounding the fire (if a
waterway bottom exists) are vertical, and consequently a very

* It can be plainly seen that it is at the boiler and not in the pipes
where the greatest amount of dirt accumulates, as the boiler is at the
lowest point, all pipes sloping down towards it.

74 Warming Buildings by Hot Water.

Fig. 99.

small proportion of the deposit adheres here, as the major
portion of it falls very naturally straight down, which carries
it below the highly heated area. On the other hand, if the
boiler terminated on a level with the fire-bars, as is most usually
the case, practically the whole of the deposited matter must
collect just at the point where the greatest heat is felt, con-
sequently it becomes exceedingly hard, and the quantity soon
becomes sufficient to keep the water away from the iron, and
a fracture ensues. In addition to the obvious disadvantage
of terminating the boiler at the furnace bars, which practically
assists the deposit in injuring the boiler, there is another
drawback in the fact that at the angle immediately nearest
the firebars there has necessarily to be a weld or joint, a
weak point where it should be strongest, but which of course
is remedied by carrying the waterway down below.

What should be aimed at is to prevent a collection of
deposited matter of any description
being formed in close proximity to
the firebox, the only place where it
can have an ill effect ; the deposit
is practically harmless above or
below where the glowing fuel is
situated. A further advantage in
continuing the waterway to the
bottom and making the boiler in-
dependent of a base is, that occasion-
ally a leakage of gaseous products
may take place between a boiler and
its base, and if any part of the boiler
is in the house these gases would
prove objectionable. But this could
only occur when a downdraught
manifested itself in the chimney.

Fig. 99* shows in section the " Ivanhoe " boiler, another
of the class that is suited for building in the thickness of a

* From the catalogue of Messrs. Robert Jenkins & Co., of Rother-
ham.

Boilers.

175

Fig. 100.

wall as illustrated. In most respects this is similar to other
boilers of this character, the chief variation being that with
the small sizes only the inner side, the back, has a waterway,
the front and right and left side being iron and fire-brick, but
to increase its effectiveness the waterway can be continued
round one or both sides. This boiler
has the advantage of having a very good-
looking shape, which adapts it either for
fixing in a wall or standing clear (in a
potting shed or adjacent outhouse).

Fig. 100* is the well-known welded
dome-top boiler, the dome having the
flow-pipe on its apex, which decidedly
favours better results than when the
flow-pipe has to start horizontally from
the side. This is a boiler which is
greatly benefited by having the water-
way continued to the bottom, parti-
cularly in the larger sizes, it being
made to heat from 350 to 3250 feet of
2-inch pipe (theoretical). This boiler,
as in fact all boilers, should have a
proper complement of mud-holes. Two

are not sufficient with a cylindrical boiler like this, as it is so
difficult to get any instrument, even a cane, to pass round the
circular sides to disturb the sediment. Three or four holes
should be provided, and if the sediment is likely to be hard,
manholes and not mudholes should be put.

Fig. ioit is a description of boiler that is worthy of every
commendation, being powerful (heating from 800 to 2200
feet of 2-inch pipe), and very compact in shape. This is in
reality a saddle boiler with terminal or waterway ends back
and front, a boiler that will be strongly recommended when
treating of brick-set boilers. The waterway front end, how-

* From the catalogue of Messrs. Graham & Fleming, Halifax
(England).

t Also from Messrs. Graham & Fleming's list. ^C2^*~.

k Of TffiR

IVBESITT;

fcjfc_^ i

1 76 Warming Buildings by Hot Water.

Fig. 101.

ever, necessitates a top feeder as shown, not that this is a
disadvantage by any means, quite the reverse, as it enables
the boiler to more readily be charged with fuel to last several

hours without attention. Hori-
zontal boilers can of course be
charged with fuel in this way
without a top feeder, but this
latter arrangement makes it
more easily done, practically
as easy as with a vertical boiler.
This boiler is more easily
cleaned than the circular ver-
tical shape, but it would be
none the less better for having
the waterway carried down be-
neath the firebox as recommended. This shape of boiler is in
many respects preferable to the vertical, with exception as to the
space it occupies. If space has not to be economised, then it
is the best to be used of the two. This boiler is of a square
shape in cross section, which makes the heating surface above

the fire flat. This is no objection,
the dirt does not accumulate at
that point, the circulatory move-
ment of the water prevents this,
and no provision need be made
for cleaning at the top part of the
boiler.

Fig. 102* is another boiler
similar to the last, but without
the waterway front. This can,
of course, be had or omitted just

as the user wishes, but, as shown, no top feeder is actually
needed if the waterway front is not used. This illustration
is chiefly introduced to show the waterway tube that passes
from side to side across the fuel chamber. This is an addition
that never fails to materially increase the heating power of

* Also from Messrs. Graham & Fleming's list.

Fig. 102.

Boilers. 177

the boiler, as it is wholly direct heating surface, and situated
at a point where it cannot fail to receive the full benefit of
the heat, at some times being almost enveloped with fuel in
a glowing state.

Sometimes these cross tubes are quite horizontal, but
there is no doubt that some benefit accrues by letting them
slope from side to side, which is the usual way they are fixed.
In either case cleaning holes should be placed on one or both
sides of the boiler, opposite the terminations of the tube or
tubes, not that any noticeable amount of soft or dirt deposit
will be found here, but that any incrusted deposit that may be
formed can be removed, for with powerful boilers the amount
of water evaporated is a fair quantity in six months, particu-
larly if the boiler is fully powerful and overheats sometimes,
and more particularly if any water is drawn out of the
apparatus for the gardener's use. In this latter case con-
siderable attention must be given to the cross tubes, as they
generally get incrusted more quickly than any other part, and
are a great source of trouble if fractured. Of course these
latter remarks only apply to the use of hard waters, but with
soft waters holes should be provided that the tubes may be
examined when the bottom of the boiler is being cleaned out.

The next, and last, description of independent boilers to
be noticed are those made by Jas. Keith, being widely different
in character to any we have mentioned yet, and having many
novel and decidedly advantageous features in them. Fig.
103,* "The Challenge," is perhaps the best known of the
boilers made by this firm. This is made of cast iron, in
square ring sections which are placed one above the other,
the parts which come together being turned and faced true,
so as to easily effect a perfect joint. The particular gain
resulting from its sectional construction is that the interior
can be so readily made of any varied shape that may be
considered to give the best results, that is to arrest and cause
absorption of the heat, a result that cannot be arrived at in a

* From the catalogue of James Keith, Holborn Viaduct, London,
and of Glasgow and Edinburgh.

178 Warming Buildings by Hot Water.

boiler wholly made in plates, which can only give us plain
flat surfaces as a general rule.

These sections take more than one form, those near the
fire being less complex than elsewhere, to facilitate cleaning.

Fig. 103.

Those forming the upper part of the boiler are much like
gratings, the cross bars being water tubes, so that the
products of combustion by the time they arrive at the flue
outlet of a tall boiler have very little useful heat left in them.

Boilers. 1 79

It must be noted that the arrangement of these different
heating surfaces has been very judiciously arrived at, so that
there are no collecting points for deposited matter, all water-
ways being kept of a vertical shape and well arranged. The
use of sections in this case introduces another convenient
feature in the fact that the section having the feeding door
in it can be placed at any height, so as to make it possible to
charge the boiler with a quantity of fuel, or not, as required,
but for the most powerful results it is better to have the firing
door at the low point.* There is not the least doubt that the
large amount of direct heating surface obtained must produce
a most rapid circulation in the boiler itself, and there is the
possibility that this, in a very great measure, prevents sedi-
mentary matter being deposited. But this is rather a dis-
puted question at present, and the writer unfortunately has
not yet had an opportunity of arriving at a sufficiently satis-
factory solution of the question. Theoretically it is right,
but practically it may show different results, and if in practice
it is found that a very rapid circulation prevents the deposit
resting anywhere, it would only apply to suspended matter
and not to the hard deposit from lime, &c., in solution.

These boilers are made to heat up to 7000 feet of
4-inch pipe (if miles), but it is very necessary that they
should be coated or surrounded with some material that is a
poor conductor of heat, otherwise a serious waste of heat must
necessarily occur.

Fig. 104! is a boiler of a very powerful character, as the
internal heating surface consists, not only of the shell sur-
rounding the fire, but also of vertical tubes, and a saddle

* It will be readily understood that when any boiler is filled up with
fuel a deal of the inner or direct heating surface must be shielded from the
heat by the mass of fuel laying above the active part of the fire, and at
this time it is the parts of the boiler that have the red fuel resting against
them that do all the work. Of course, by urging the fire the whole mass
could soon be got into a hot state ; but this is not done as a rule. When
the charge of fuel is partly burnt and sinks down, the upper heating sur-
faces then experience a benefit.

t Also from Mr. Keith's list.

N 2

1 80 Warming Buildings by Hot Water.

overhanging the fire in such a way as to receive the greatest
possible benefit of all heat and heated products. The interior
surface of the boiler constituting the fire-box is ribbed, and
the bottom grating is fitted so that it can be shaken (rocked)
to clear the fire from ash, &c.

Fig. 104.

The illustration gives a very clear and sufficient explana-
tion of the external portion of the boiler, but it may be
pointed out that this pattern can also be had with the water-
way carried down and beneath the fire if required. This
makes the boiler safe in use on an inflammable floor (sup-
posing it is never fired when empty, a most unlikely occur-
rence), and it permits of pipes being carried to the boiler on
the floor level without dipping them. This, also, is of con-

Boilers. 1 8 1

siderable use and convenience when pipes or radiators upon
the same floor level as the boiler have to be heated.

This boiler is of cast iron, and made in varied sizes to
heat from 200 to 3000 feet of 2-inch pipe. The feeding
door is situated so that the fire can be charged with fuel to
last several hours when desired.

1 82 Warming Buildings by Hot Water.

CHAPTER IX.

BOILERS, FOR BRICK SETTING.

Saddle boiler and modes of setting it fully described Water bars and
connecting Check ends and waterway fronts Cross tubes Flued
saddle boiler The " Colonial " boiler The " Climax " boiler The
"Imperial" boiler The "Delta" boiler The "Excelsior" boiler
WagstafPs tubular boiler The " Champion " boiler Week's tubular
boiler Water bars for coil and tubular boilers The " Python " boiler
The Trentham Cornish boiler.

THE chapter just finished dealt almost exclusively with
boilers of the independent kind, and which require no brick-
work in their construction or setting (unless it is desired to
build them in a wall, or to jacket them with brickwork). It is
now proposed to treat of those that are dependent upon the
bricklayer for their erection, setting, and subsequent efficiency.
The independent boilers shown constitute but a small portion
of the great variety that are made, but enough has been said

to illustrate the features that
may be considered essential and
good or bad in them.

The boiler that must take
precedence in the following list
is the "Saddle," Fig. 105. This
shape stands high in every
one's esteem, for it has been
tried in every conceivable way,
and found satisfactory. Hood
praised it at least twenty years ago, and it is in favour still ;
and very many, most in fact, of the new designs of wrought
boilers introduced follow the saddle shape to a great extent,
as will be seen as the chapter progresses.

Boilers for Brick Setting.

183

The particular features in favour of the saddle boiler are,
firstly, of all wrought-iron boilers it is about the cheapest to
make ; its shape is particularly adapted to receive and benefit
by the heat evolved, especially the direct heat, which is the
most valuable and effective, and it is found in practice that
this shape is free from the faults that are brought to light
from time to time with the many new shapes introduced.
The saddle shape, however, is not usually adopted for
works that exceed, say, 800 to 1000 feet of 4-inch pipe,
as it is beneficial to bring the heating surface within a
limited area, so that it may profit fully by the heat radiated
from the fire, and this is effected by adding waterway ends,
cross tubes, &c., which greatly increase the power of the
boiler without increasing the size, as has been already ex-
plained. If we used a very long saddle boiler it would
necessitate our greatly increasing the length of the fire if
we wished the whole internal surface to receive a full share of
the radiant heat which is so necessary for good results.

From the illustration (Fig. 105) it will be noticed that
from a point about half way up the boiler, the top describes an
almost true half circle, both outside and inside, but to the
writer's mind greater effect would be obtained if the boiler
was made more square in shape so that the inner the direct,
and most valuable heating sur-
face would be added to, and
the vertical flue surface would
be increased, the vertical sur-
face doing more effective work
than that which comes beneath
the heating products as is the
case with all the outside
rounded portion of the ordi-
nary saddle boiler. Fig. 106
illustrates what is meant by

making the boiler square in shape, and it will be readily seen
that the internal and external surface is added to, and of
course the quantity of plate used is increased proportionately.

Fig. 1 06.

1 84 Warming Buildings by Hot Water.

There is not the least doubt that the top outer surface of
a boiler, whether it be round or flat, is of little value, as in
the first place every one knows what little useful effect is pro-
duced by applying heat to the top of a vessel ; and secondly
the top of the boiler of either shape has always a coating of
dirt or soot upon it (except immediately after it has been
swept clean), and this dirt material is always of a low con-
ductivity, so that it permits of little heat passing through
the boiler plate to the water.

In the square shape of boiler the top surface could still be
made use of if desired, but it must be contended that by
placing the mid-feather half way up the side of the boiler and
causing the flame to travel up and down the side only, better
results will be obtained than if any part of the side surface is
neglected for the sake of passing the heated products over the
top. With the shape under discussion the top need not be used
at all (unless particularly desired). There is ample vertical
surface for the heat, with an ordinary draught, to act upon,
and every one must admit that however low a value vertical
surface has, it is more valuable than any surface that comes
beneath the source of heat, the source of heat in each case
being equal. If, with this square shape, no use was made
of the top outer surface the cost and labour of fixing would
be reduced to a small and simple affair, as no arch would be
needed.

As before mentioned the " saddle " boiler has always been
found very effective and satisfactory for many general pur-
poses, as it is free from complexity ; and it is somewhat ex-
ceptional for it to be set wrongly, as it has become so well
known and used by all classes of heating engineers. The mere
fact of the knowledge of its proper setting being so general
has doubtless gone far to effect its recommendation, as many
engineers, especially those who have no very extensive prac-
tice, are naturally somewhat shy of the newer patterns of
which they have had no experience. But as before mentioned,
however much the " saddle " shape may be esteemed, it is not
suited for large works, as for economical and rapid results we

Boilers for Brick Setting.

185

must have the direct heating surface as extensive as possible
close to the fire, or next best to this, have flues constructed
within (i. e. through) the boiler itself where the heated gases
can do effective work almost immediately they leave the
burning fuel, and before they can have possibly lost heat.

There is more than one method of setting a saddle boiler,
and for the smaller sizes it is doubtful if leading the flame to
and fro, the length of the boiler, is so satisfactory as the
following way, which permits all heated gases, &c., to escape
at all points around the boiler, and envelope it so to speak.

This method is to have the furnace bars, dead plate, and
other fittings in their customary places, but instead of the
boiler standing level with the fire grating it is placed upon
four firebricks, one at each corner, forming four feet, which
raise the boiler about 3 inches above the level of the bars ;
and instead of bringing the boiler tight against the front
brickwork, and also partially closing up the back portion, it
is simply stood so as to come within, say ij to 2 inches of the
brickwork at either end, with a clear space of 3 to 3 J inches
up each side and over the top.

Figs. 107 and 108 show the arrangement in length and
cross-sections, but the position of the chimney requires con-

Fig. 107.

Fig. 108.

sideration, as it must always be remembered that the action
of the draught induces the flame and heat to take the
shortest or easiest route, if there are two or more ways

1 86 Warming Buildings by Hot Water.

unequal in length or size, &c., by which it can pass. In the
illustrations the chimney is shown, built to pass off as near as
possible, centrally over the top of the boiler, and supposing it
were situated exactly over the centre and the flue passages up
the boiler sides were equal in size, the boiler would heat about
equally all round. If, however, the chimney was not so
situated, steps would require to be taken, by means of de-
flecting plates, &c., to cause the flame to distribute itself
generally in all directions as it passed away from the fire.
But this arrangement is only suited for small boilers, and
unless the circumstances appeared very favourable the writer
would not recommend this method as against the customary
way of conducting the flame up and down the boiler side as
next to be explained. It must also be pointed out that when
a fire has been going quietly for several hours there accumu-
lates a quantity of ash on the fire-bars and this would some-
what interfere with the free passage of heat to the outer or
indirect heating surface of this boiler by choking the way
along the bottom each side.

It will be understood that the reason for giving a ij-inch
space between the front and back ends of the boiler and the
brickwork, is to prevent the flame having too free a passage
in either of these directions to the prejudice of the outer side
heating surfaces ; and if the chimney was situated at the back
end of the boiler (could not be carried otherwise) instead of
centrally over the top, then it would be better to let the back
end of the boiler butt tight against the brickwork, without any
passage way being left at this point.

The most customary and, at present, the best way to set a
saddle boiler of any size, is to provide flues passing to and fro
along its outside as follows : The boiler is placed upon a level
with the furnace bars* and so as to come tight up against the

* Any direction as to the height of the furnace bars is rather unneces-
sary, as the position for these is fixed by the make of the furnace fittings,
that is the front, with fire doors, and the other articles that constitute the
set of fittings, which are purchased complete from the boilermakers or
elsewhere, and which show exactly where the furnace bars are to come.

Boilers for Brick Setting.

187

front brickwork, that which the front fittings are fixed against,
making a flame-tight joint at this point as Fig. 109.* This
brickwork will be 9 inches thick. The furnace bars, in
addition to having their upper surface on a level with the

Fig. 109.

SECTION OH E. F.

bottom of the boiler, are so arranged that the front extremities
of the bars are exactly in a line, vertically, with the front of
the boiler, the dumb or dead plate extending from the bars to
the furnace door as shown, and this plate should come exactly
level with the furnace stoke hole, so that all the parts that
constitute the bottom of the fire-box, where the fuel rests, are
on a level from end to end right through as illustrated.

The bars usually occupy about two-thirds the length of
the fire-box (see area of fire-bars, p. 155), resting at one
end on the dead plate, which should be rebated to receive
them, and at the other end on a bearing bar on or in front of
the solid brickwork which extends from this point, the rest
of the way to the back.f The back end of the boiler does

* From the catalogue of Messrs. Robert Jenkins & Co., Masbro' boiler
works, Rotherham.

t The furnace bars are always kept forward, so that the whole of the
direct heating surface may have the full benefit of the heat before it passes
to the flue entrance.

1 88 Warming Buildings by Hot Water.

Fig. no.

not come against the back wall, but is kept from 5 to 7 inches
away from it to admit of making the proper passage way
from the interior of the boiler to the outer flues.

Between the boiler and brickwork at back is built a fire-
brick bridge or check end (to check the too free escape of

heat, &c.) extending from
side to side as shown on
the plan drawing Fig. 1 10,*
and reaching quite half
way up the arched opening
in the boiler, as shown in
the last illustration. With
small boilers a thick fire-
brick slab is occasionally
used for this purpose. This
bridge fulfils another useful
object in forming a bound-
ary to the fire-box, as were
the side flues to have their
entrances low down the
stoking of the fire would
quickly cause them to get
partially stopped with
cinders and debris.

Above this check end, another bridge has to be made to
prevent the exit of flame from the upper part of the arch into
the upper flue above the mid-feathers. This bridge may be
made with a large firebrick if the boiler be of limited size,
but usually it consists of an arch formed in firebricks, as will
be fully explained shortly. The illustration shows the direc-
tion the flame has to take, the arrow passing sharp round to
the outside of the boiler, below the mid-feather, the position
of which is indicated by the dotted lines.

Fig. no| shows m P^ an ( at a point just below the mid-

* This bridge usually extends right to the brickwork each side, nothing
is gained by keeping it just the width of the boiler,
t Also from Messrs. Jenkins and Co.'s catalogue.

Boilers for Brick Setting.

189

Fig. in.

SECT I ON \ONA.B.

feathers) the position of the lower firebrick bridge with arrows
showing how the flame passes to right and left around to the
outside of the boiler within the flues referred to. The extent
of the side flues, the position (in plan) of the two lower soot
doors, the fire-bars, and
dumb plate, &c., are also
clearly shown.

Fig. 1 1 1 * shows the
same boiler in sectional
elevation, the section being
across the front of the
furnace bars. It will be
noticed that the brickwork
forming the bottom of the
side flues is also on an
exact level with the bars,
so that at the moment the
fixer is about to place the
boiler in position, the erec-
tion, as far as he has proceeded, is about 12 inches high, and
perfectly level from side to side, and from end to end. At
the back end of the boiler will be seen the bridge already
referred to ; and the flow pipe proceeding from the top, and
the return entering the side are also shown clearly; the
return pipe can of course be brought in either side, or one in
each side if desired, but the position of the return pipe will
be further referred to directly.

The most important features in this illustration are the
mid-feathers, and the arched flue-way which the mid-feathers
divide into three parts. These drawings are not to scale, so
no accurate result can be arrived at by comparing any portion
with the size of the bricks of the brickwork, and it will be
noticed that the flow pipe, assuming that it is 4-inch, is out
of proportion with the size of the boiler. This is merely
mentioned as it is so customary and natural to judge ap-
proximate dimensions by comparison. This flueway, at sides
* Also from Messrs. Jenkins and Co.'s catalogue.

1 90 Warming Buildings by Hot Water.

and top of boiler, as here shown, and which appears on the
other drawings, must be of a proper size (width) as, if too
small, it will choke the passage of flame, and with coal fuel it
would be soon stopped with soot ; if too large, the flame or
heated gases will not have their full useful effect, for (as
already explained) flame has a most pronounced tendency to
float between surfaces without having contact with them
where it is possible, and as flame radiates but a very small
amount of heat, it is very necessary that it should be made
to impinge or have contact with the parts to be heated.

When the flame leaves the interior of the boiler at the
back, the direction in which the draught impels it to travel,
makes it hug, or cling to, the sides of the boiler, so as to
neutralise to some extent the inclination which flame has to
avoid contact with surfaces, but notwithstanding this if the
flue were too wide little contact would take place. When the
flame ascends from the side flues, in front, and passes into
the flue over the top of the boiler, the flame, following its
natural tendency, is inclined to seek the highest point and
does more towards heating the top brickwork than heating
the boiler top.

All these arguments go to show that the flues must be
restricted in size, and as a general rule 4^-inch is the size
that should be adopted.

This size is subject to variation to some extent as the
boilers vary in size. 4-inch or even 3-inch would suffice for
the smaller boilers, say less than 3 feet long, and in those of
large size, a 6-inch flue would be better suited. It may be
considered that the majority of plain saddle boilers made
measure between 3 and 6 feet in length ; many are of smaller
and larger sizes than this, but they do not represent the
majority by any means, and between these two sizes a 4j-inch
flue is suitable.

The mid-feathers extending from the end of the boiler to
within about 6 inches of the front, as shown by the dotted
lines on Fig. 109, can be made of firebrick, iron plate, or, if
desired, the boiler maker will make a waterway through them,

Boilers for Brick Setting.

191

Fig. 112.

as Fig. 112. They are most commonly made of firebrick, as

if iron is used it should be affixed to the boiler by the maker,

which may cause delay. It is quite possible to support an

iron mid-feather from the brickwork, although it is not such a

satisfactory job as when riveted to the

boiler. The waterway mid-feather adds to

the total efficiency of the boiler, but it is

doubtful whether the gain effected is in

full ratio with the increased cost. If

waterway mid-feathers are used, it is very

necessary to order them to the position

required, otherwise they will be most probably placed, as at

Fig. 83, which in the writer's opinion is not so good as

placing them as Fig. in.

The position of the mid-feathers, i. e. the height at which
they are placed, needs to be considered -with the view of
getting the best work from the fuel expended. It has been
most commonly the practice to place these feathers at right
angles to the sides of the boilers at the point where the curve
commences, as at Fig. 83, just referred to ; but the ultimate
effect can certainly be increased by placing them higher up,
giving more surface for the heated products to act upon
immediately they leave the fire, instead of devoting more
space to the top flue, where the heat does less work, and is to
a great extent expended when it reaches there. In the
illustration now under discussion (Fig.
in) the feathers are shown fairly
high, but they might advantageously
be placed just a trifle higher than
this, as Fig. 113, so as to leave the
top flue barely larger than the two
side flues. This will have a judi-
cious choking effect to the top flue
and help to bring the heat into more effectual contact with
this surface, which so usually escapes to a great extent by
reason of all heated gases having a tendency to keep clear
of surfaces beneath them if there is sufficient room to permit it.

Fig. 113.

192 Warming Buildings by Hot Water.

Fig. 114.

Occasionally a workman will be found carrying the front
end of his mid-feathers down a little way at right angles, as
Fig. 114; this has a good effect in causing the flame to spread
itself more over the side surfaces, as with a high mid-feather,

the flame and gases always
seeking the highest possible
point, and the draught al-
ways taking the very shortest
and nearest passage it can,
partly prevents the lower
portion of the boiler sides
being acted upon, as the flame
would be found to pass rather
closely under the mid-feathers
if this turned down portion

did not exist. Of course this improvement is not a necessity,
but an improvement it really is, and adds a trifle to the total
efficiency. The feathers must not be turned down very far, or
they will interfere with the proper cleaning of the boiler (flues)
outside, which is particularly necessary if the fuel, or any
part of it, is coal.

Before leaving these side flues it is desirable to point out
that there is a point at which the return pipe (or pipes) should
enter so as not to cross the flue, and, firstly, be no obstacle
to the soot 'or flue-raker, and, secondly, be no means of

checking or reversing the cir-
Fig. 115. . culation, as putting the return

pipe in a highly heated place
would be likely to do. The
point referred to is low down
in the side (as usual) at the
back ; at this point the return
pipe can be neatly covered

with brick and cement work, as Fig. 115; this obviates both the
objections named. Nearly every boilermaker's illustrations
show the return pipes connected into the middle or towards
the front, but the back is decidedly the best in every way, as

Boilers for Brick Setting. 193

it does not block the flue. If Fig. 1 1 1 is referred to, it will be
seen how awkwardly the return pipe would be placed, if we
suppose it to be brought in anywhere near the front.*

The arrangement of flues at the back of the boiler has
already been referred to, but it is necessary to deal with it
further, so as to make it clear how this part of the setting is
carried out, for it is perhaps the most difficult point to those
who have no experience. It has been explained (p. 188)
that, in addition to the fire-brick bridge, which reaches from the
bottom to about half way up the back of the boiler, there is
another bridge carried across just above this with the view of
stopping all passage of flame directly into the chimney above,
and so causing it to pass around to the sides of the boiler
beneath the mid-feathers.

The construction of this upper bridge requires both care
and skill, as although it is a common practice to carry this
brickwork straight across, support-
ing it on iron bearing bars, as Fig. Fl &- II6 -
1 1 6, this is in the end a very
unsatisfactory arrangement, as the
bars must some day, sooner or later,
be affected by the heat and gradu-
ally give way, and by this gradual
collapse, choke, and eventually
stop the passage - way between
the two bridges in question. Hood recommended a solid
fire-lump for this purpose, as Fig. 117, which is his original
illustration of the back of the boiler with the bridges in situ.
Fire-lumps, however, are hardly practicable for large wide
boilers on account of the expense or difficulty in getting them
when the work is away from large towns (as it usually is).
The upper bridge can be better made of fire-bricks, without
a bearing bar, by making it arched, as Fig. 1 1 8. This arch
should commence on a level with the feathers, these being

* It is desirable to keep the flow and return pipes as far away from
one another as possible, as this prevents to a great extent collections of
sediment and other objections to be explained directly.

i 9 4

Warming Buildings by Hot Water.

brought right through just below it to as far as the back
brickwork ; and supposing this arch bridge to rest on the
edge of the feathers, as this explanation suggests, then they

Fig. 117.

must be well supported by brickwork gathered out from the
back, as Fig. 1 19. It will be noticed from Fig. 1 18 that the top
of this arch-bridge is level with the top of the boiler ; this

Fig. 119.

Fig. 1 1 8.

permits the top flue to pass right over it, supposing the
chimney to be quite at the rear ; but when the chimney starts

Boilers for Brick Setting. 195

away from the top, as Fig. 109, this bridge is sometimes
carried over, resting on the edge of the boiler, as is shown
there. A little better joint between the boiler and brickwork
is effected this way, but it is not the best plan if the chimney
starts upright at the back, although it could still be done
then. In this drawing, Fig. 109, the bridge in question is
made by bricks placed lengthways from front to back, about
i inch resting on the boiler, and 2 inches in the brick-
work at the back. This leaves a 6-inch space, which is
sufficient with moderate sized boilers, but it might advantage-
ously be made 8 inches in the larger sizes. Roominess at
this point, from front to back, is desirable ; at other points it
is objectionable, as explained.

The pit in which the boiler is situated can be either of
brickwork or concrete, and sometimes they are lined with
iron, but with none of these materials can the pit be kept dry
if the drainage is shallow ; that is, if water is found in the
earth at a higher level than the bottom of the pit. This
necessitates the use of special shallow boilers (see p. 204)
unless the house which the boiler is to heat is by some
unusual circumstances raised up somewhat. In any case,
every effort should be made to drain the pit, as even with
good ground water may find its way into the pit from various
causes, and as the pit is very commonly in an exposed place
provision to shelter it from rain and general inclement
weather, must be made.

In building in the pit it must be made of such a size as to
admit of the stoking tools being used freely, although shift
could be made as regards this if absolutely necessary. The
size of the pit is governed by the size of the boiler, and on
this account, if the situation of the pit is peculiar, thought
must be bestowed upon what space the boiler may be allowed
to occupy. A " blow-off " cock for emptying purposes must
be provided from the boiler in the pit, and, as explained, the
plugged pipe ends should appear in front, see Fig. 86, so
that the accumulated sediment in the boiler can be disturbed
with rod or cane inserted through these pipes.

O 2

196

Warming Buildings by Hot Water.

Fig. 1 20 * shows the front in a finished state as it appears in
the pit, with sweeping doors opposite the two sides and the
top flues, the flow and return pipes, and the damper in the
chimney in place.

Fig. 120.

All the brickwork that is acted upon by the flame and
heat should be built up in good quality firebricks. The other
brickwork that is not acted directly upon by the heat can be
of the ordinary character. The arch that is carried over the
top of the boiler, corresponding in radius with the boiler top,
is very commonly made by first building the sides up to the
mid-feathers, then, after fixing these in position, the boiler top
is covered with ashes or dry earth to a depth that the flue is
to be, say 4^ inches, then the bricks are carried over, resting
on this material, which is afterwards raked out when the
brickwork has set. This is a most simple way of making the
arch without the use of special appliances.

The iron furnace front is secured to the brickwork by
clamps, but inserting these in the ordinary way is not always

* Also kindly loaned by Messrs. Jenkins & Co. This illustration does
not show the cleaning plugs that should appear in front.

Boilers for Brick Setting. 197

sufficient to keep the front soundly secured, the general effects
of the heat tending to loosen it. Some fixers will have
clumps extended from the furnace front right through, and
clipping round the rear end of the boiler ; this usually makes
a good job of it, and it can be taken as fair evidence of skilled
workmanship if the furnace front keeps sound and tight
against the front brickwork after the boiler has been in use a
little time.

There are variations to the method explained for setting
saddle boilers. Some engineers consider that better results
are attained by first carrying the flame over the top of the
boiler from back to front, immediately it leaves the interior,
and causing it to descend and pass along the sides under the
mid-feathers to enter the chimney. This arrangement has
merits probably, or it would not be resorted to ; but the
writer has not discovered them, and certainly the results
cannot be so satisfactory as by the method which has been
fully explained, and which has by far the major shs^ of
approval. The particular objection to it in the writer's eyes is
that it devotes the best services of the flame and heat to the
top of the boiler, where it has the least useful effect, even
supposing it was kept scrupulously clear of ash-dust and such
matters.

Sometimes a workman will bring his mid-feathers right up
to the front end of the boiler and make provision for the flame
to pass from the lower to the top flue by a recess in his front
brickwork opposite the feather ends ; no particular gain results
from this, if anything it interferes somewhat with the removal
of soot or dirt from the top flue unless other soot-doors were
provided, it being swept down into the lower flues in the
usual way.

It was explained on p. 187 that from the lower edge of
the furnace door, right across the fire-bars to the back was an
exact level. This is not always the case, as sometimes a fixer
will make his dead plate slope down towards the fire-bars, so
that the bars and the bottom of the boiler resting upon them
are below the bottom edge of the furnace door, perhaps

198 Warming Buildings by Hot Water.

three inches, reducing the height of the ash-pit to this
extent. This arrangement is usually resorted to only when
it is desired to keep the boiler as low as possible, or, in
other words, to work in the shallowest pit that can be used
efficaciously, and for this purpose the method is a good and
practical one.

The chimney, if brick, should not be less than 9 by 9 inches
(inside) for moderate sized boilers ; for the largest sizes 14 by 9
or 14 by 14 is desirable. A very common error is fallen into
in making chimneys too' small ; these will be dealt with fully
under " Chimneys," on a later page.

There remains to be mentioned that occasionally it is
desired to use water-bars to the furnace instead of the ordinary
solid bars ; and in this case the return pipe or pipes do not
enter the boiler at all, but enter the box end of the bars in
question, and from thence circulating into the boiler, as here

shown (Fig. 121). These

Fig. 121. bars keep more free from

clinker than the ordinary
solid bar, as they are al-
ways kept at a lower tem-
perature by the water with-
in them, and they add to
the heating surface to a fair
extent, though not so much
as would be the case if they
were always clear of ash,
which, however, cannot be

expected. Commonly, the returns are brought into the
front box end of the water-bars, as shown, and this is the
best ; but, instead of their bringing the connecting pipes into
the front end of the boiler they might just as well enter the
back,* so as to be no obstacle in cleaning the flues. The
pipes forming the bars are cast much stronger, heavier, than
the pipes used for radiating purposes, they are also smaller.

* The positions that the flow and return sockets occupy on nearly all
illustrations of boilers in the makers' lists is the flow near the back end

Boilers for Brick Setting.

199

They cannot be cleaned out ; their strength, however, goes
far towards saving them from ill results, even supposing they
became solid with deposit.

The first improvement on the saddle boiler was in making
it with a waterway check end, as Fig. 122. This was a decided
gain by adding considerably to the direct heating surface,
and also to the flue surface at a point where the heat has its
greatest effect after leaving the fire-box. This in no way
affected the labour in fixing, except to lessen it a trifle,
and the cost is increased to but a reasonably small extent if
we compare one of these with an ordinary saddle of similar
power (not similar size).

Fig. 122.

Fig. 123.

The effectiveness was further increased by putting a water-
way front to the boiler (as well as a waterway end), as Fig. 123,
but this introduced a new feature that had to be provided for,
viz. the inability to attend to the fire at all successfully from
the front, as the furnace door gave but little access to the
fire-box, except for raking out clinker, &c., and therefore a
door for feeding or banking up had to be placed elsewhere ;
this is best if put in the top, as shown at Fig. 101.

and the returns near the front, the contention being that this arrangement
causes the water to circulate more uniformly through the boiler, entering
one end and passing out at the other. The contention is a good one, as it
will prevent as much as possible large accumulations of sediment occurring
in certain parts of the boiler, and it will also prevent any violent internal
circulations taking place ; but for general purposes it will be found better
to have the returns entering the back and the flow off the front at top.

2oo Warming Buildings by Hot Water.

This form of boiler is in character with Hood's standard
of efficiency, and even at this moment it is considered, and
worthy of being considered, good, and capable of giving good
results, although of course there are many new features since
introduced that go to increase efficiency without materially
increasing size.

Perhaps, one of the earliest ways of adding to the effec-
tiveness of a boiler of any description (saddle, Trentham, or
vertical) was the addition of one or more cross tubes, as
Fig. 1 24 ; * these are wholly direct heating surface, and being

Fig. 124.

in, or nearly in contact with the glowing fuel, a very decided
gain in heating efficiency is effected. This can be readily
judged from a maker's catalogue, in which this boiler, 36 by
1 6 by 1 6, is listed to heat 1050 feet of 4-inch pipe, and a plain
saddle boiler to heat this same quantity requires to be 48 by
1 6 by 1 6, one-third longer than the other. It is, however, not
particularly desirable to introduce these cross tubes unless it
becomes from some cause necessary ; and for small works it
is better to have a plain boiler, the cross tubes being merely
one of the different devices for adding to the power of the
boiler without making it of unwieldy size.f

* From the catalogue of Messrs. Graham & Fleming of Halifax.

f If the writer is found to speak in greater favour of one boiler than
another, it is not intentional ; all the boilers being noticed have some good
features of their own, and none are introduced that have been found defec-
tive x>r practically weak, it also needs to be mentioned that no one can

Boilers for Brick Setting. 201

Fig. 125 * shows a further addition to the saddle boiler, in
the top flue way, which is within the boiler itself, and does not
come within the category of the top flues deprecated by the
writer when speaking of the value of flue surfaces, and again

Fig. 125.

later under the heading of " Saddle Boilers." This top flue
allows of the flame and heated gases coming beneath a water
surface, and by this means we get the most efficient of all
flues, giving better results than the vertical side surfaces.

Several makers' lists show this boiler in section with the
flame travelling through this flue from back to front, and then
passing from the front over the top of the boiler to the chimney,
as Fig. I26,t the object of the illustration (in the catalogues)

safely recommend one boiler to the exclusion of all others, as many of
about an equal degree of efficiency are made, and, consult as many
authorities as you will, they will all differ to some extent as to the merits
of different kinds. Again, architects who have to deal with heating
works, have different ideas as to what should be specified, some going so
far as to design new boilers for their own purposes ; and all these differ-
ences in opinion of course account for the really vast variety of boilers
that are now put upon the market. It is also peculiar that certain patterns
will occasionally be sought after very greatly for a short time and the
demand then cease, and some other pattern have the increased call.
Certain patterns, furthermore, are favoured in certain localities.

* From the catalogue of Messrs. Lumby, Son, and Wood, Limited,
Halifax.

t This boiler is made with or without a terminal end, but the former is
much to be preferred, as illustrated.

2O2 Warming Buildings by Hot Water.

being to show the method of fixing. Now, with an ordinary
draught in the chimney there is no objection whatever to
carrying the flame * down from the front and back along the

Fig. 126.

Fig. 127.

two sides, using a vertical feather, as Fig. 127^ This illus-
tration shows a similar boiler with waterway front, neces-
sitating the top feeder which is carried through the flue-way,
as shown. It must not be forgotten in setting these to provide
the sweeping doors opposite the flues, as described with the
saddle boiler, and one is particularly needed opposite the top
flue-way through the boiler, as a deal of dusty matter will be
deposited here from coke, or soot from coal. The boiler just
illustrated has a large demand, as it is very powerful, and has
no objectionable features ; it is also well suited for shallow
drainage, and is economical of space for the results attained.

Fig. 128^ is another powerful boiler, resembling in some
respects the last one, but having twin flues at top instead of
the wider single one. A peculiar feature in this boiler is the

* The word flame is used very freely, and it is feared in instances
where it would be literally incorrect ; but it is a more convenient word
than "heat " or "heated gases," when dealing with flues, even though it
may apply to a furnace burning coke and producing no actual flames.

t The " Colonial," from the catalogue of Messrs. Graham and Fleming,
of Halifax (England).

J The " Climax," from the catalogue of Messrs. Hartley and Sugden,
of Halifax (England).

Boilers for Brick Setting.

203

pieces stopped out of the front termination of the top flues,
which permits of the boiler being butted tight up against the
brickwork in front, thus
decreasing in a consider-
able degree the labour in
fixing. The brickwork is
also brought down close
to the top, the top surface
not being used (the makers
recognising the useless-
ness of this surface). Fig.
129* shows in section the
simple way in which this
boiler is fixed. The neces-
sary soot doors must not
be forgotten.

Fig. 129.

Fig. 1 30 f is another boiler, adapted for shallow drainage,
and of a powerful character, but from the illustration it will

* From the catalogue of Messrs. Hartley and Sugden, of Halifax
(England).

t The " Imperial," from the catalogue of Messrs. Graham and
Fleming, of Halifax (England).

204 Warming Buildings by Hot Wafer.

be noticed that the flame is carried both to and fro in flues
within the boiler, and then to and fro along the outside, as
shown by the mid-feather. This necessitates having a chimney
with a stronger draught than the preceding.* Fig. 1 3 1 f is a

Fig. 130. Fig. 131.

transverse section of this boiler, showing its internal shape
and also the method of setting. The flame when it leaves the
fire enters the two lower side flues without leaving the boiler,
and from these it is caused to enter the top flues at the front,
and from these top flues it is conducted outside at the back,
passing under the mid-feathers, then back over the top.

Perhaps the shallowest boiler at present made for difficult
drainage is as Figs. 132 and I33,J its power being obtained by
the increase in width instead of height. This is a terminal
end boiler, and the arrangement of the flue-ways at the end
cause the flame to impinge upon the upper surface imme-
diately beneath the flow-pipe. This must more effectually
induce circulation when the apparatus is first started, and at
any time a good result is attained by causing flame or heated
products to impinge and come in contact with the boiler

* A taller chimney, see Chimneys,
t Also from Messrs. Graham and Fleming's catalogue.
J The " Delta," from the catalogue of Messrs. R. Jenkins and Sons, of
Rotherham.

Boilers for Brick Setting.

205

plates ; this is the object of the "bridge" inside horizontal
cylindrical boilers.

This must close the list of horizontal plate boilers. Amply
sufficient has been shown to make clear the general features

Fig. 132.

Fig- 133-

that at present exist in these, and although it is no exaggeration
to say hundreds of other shapes would be found if all the dif-
ferent makers' lists were collected, there is a great similarity in
the majority of them to some of those just described, and we
can therefore now describe those that have some peculiar and
novel features, and which entirely differ from those just treated,
which are generally recognised as ordinary boilers. It must
never be overlooked that the greater the length of horizontal
flues the higher the chimney must be, and the more the flues
turn to and fro the greater strength of draught and corre-
sponding height of chimney is needed. This is often of con-
siderable importance, as in so many situations a tall shaft is
by no means admissible, and an increased natural draught
cannot be obtained except by increased height of chimney
(see Chimneys).

Fig. 1 34 * shows a boiler that is considerably in favour and
is of a decidedly powerful character, presenting, as it does, all
possible direct heating surface to the fire (except what can be

* The " Excelsior," from the catalogue of Messrs. Lumby, Son, and
Wood, Limited, of Halifax (England).

206 Warming Buildings by Hot Water.

gained by cross tubes, &c.), and having almost the whole of its
outer surface enveloped in flame when in use.

The shape of this boiler particularly adapts it for with-
standing a heavy internal pressure, as is always obtained with
an apparatus that may extend up three or four floors of a
high building (never in ordinary horticultural works), in which
case it is not advisable to use the simple type of saddle

Fig. 134-

Fig- 135-

boiler as it would probably bulge out in the middle, inside,
and be ruined, perhaps even before the fire was lighted, as
the pressure becomes enormous in the boiler of an apparatus
that extends to any considerable height, and which the cylin-
drical shape is best able to withstand (see p. 255). This
argument, however, does not apply to cast-iron boilers.

Fig. 135 * shows the method in which this boiler is
fixed. The flames and heat from the interior pass out by
way of the grated opening near the top, as shown. The
grating is provided to prevent the fuel falling through into the
flue, the boiler being specially adapted for filling with a full
charge of fuel. The flame is then caused to pass down the
sides beneath the mid-feathers, then up again into the chimney
at back ; the top surface of the boiler is not made use of. This
boiler can be had with waterway mid-feathers if desired.
* Also from Messrs. Lumby, Son, and Wood's catalogue.

Boilers for Brick Setting. 207

Fig. 136* is an ingenious form of boiler that has now
been in use for a considerable time, and survived all the
criticisms and trials that a boiler is subjected to during the
few years of its existence. This is a cast-iron boiler made in

Fig. 136.

segments and bolted together, the particular features being the
large direct heating surface obtained, by what are practically
deep convolutions, and the very good way in which the heat
is allowed to pass from the furnace outside to reach the
chimney.

It will be seen in the illustration that where the sections
meet at the sides provision is made for a slot-shaped opening
to come at every joint, extending from near the bottom to the
point where the rounded top of the boiler commences. When
the boiler is in action the flame passes out through these
slots and, presuming the chimney to be at the back, as usual,
the whole of the outer surface receives the full effect of the
heat. This tends to simplify fixing, as the front and back are
butted tight up against the brickwork. Figs. 137 and 138!
will illustrate this, but in these two drawings the boiler is shown
fixed with water-bars to the furnace.

* From the catalogue of Mr. J. G. Wagstaff, of Dukinfield, near Man-
chester, t Also from Mr. WagstafPs list.

208 Warming Buildings by Hot Water.

This boiler is also made in an independent form, and to
some of the patterns in which they are constructed a top
feeder can be applied.

Fig. 137'

Fig. 138.

Fig. 1 39 is a form of boiler that is gaining favour, as it has
been subjected to some severe trials in competition with others,
and gained favour. This is a coil boiler, but differing from

those previously referred to in the
Fi S- '39- fact that it is in every way ad-

r~ "^ ~fl apted for large works. This coil

f~ jj is of cast iron built up in sections,

( j but presenting in other ways the

( ) same appearance as one of

C . ) P rv wrought-iron pipe. It will be

C ymJ noticed that the pipes forming the

coil are set down close together

without any passage way or space between them for flame or
heat to pass through, and this constitutes one of the chief
features in the patent of which this boiler is the subject, as from
a considerable experience that the inventor had (perhaps more
than any other water engineer) with coils and coil boilers, it
was found that by preventing egress of flame through the sides
of the coil but conducting outside with flues with three or
four vertical mid-feathers, a considerable improvement in
results was effected, chiefly in this instance, by preventing such
a very free escape of useful heat into the chimney as takes place

Boilers for Brick Setting. 209

with the open coil with a powerful furnace, an effect that is,
however, considerably modified with the small independent
coil boilers. By closing up the coil we certainly get a larger
surface in contact with and near the fire than we could do
with an open coil, and this undoubtedly has gone far to make
this boiler more efficient.

The usual method of fixing this boiler is to arrange for the
furnace to be within it and to lead the flame out at the top to
pass up and down the outer surface by vertical mid-feathers.
The heated products escape from the interior by a flue way
at the top of the boiler, and then, by the feathers provided,
it is led up and down the boiler, finally escaping by the
chimney which leads off at the back. These are very com-
monly fixed with a sort of auxiliary flue leading direct from
the furnace to the chimney, to draw up the fire quickly when
lighting, &c., this flue being closed by a damper when the
fire is fairly established. In fixing this boiler an arrangement
for feeding at the top is necessary ; the customary emptying
service is needed, and particular care should be given to the
easy cleaning out of deposit.

The size of the pipe constituting the coil is 3 inches, a suffi-
ciently full size, and it has to be said in favour of this boiler
that the argument as to water staying about the flat top surface
of some boilers is entirely disposed of, as there cannot possibly
be any check to the free passage of water to the pipes in this
case. The argument referred to is that in some square-shaped
boilers a rapid circulation goes on within the boiler itself, and
only a proportion of the heated water passes at once into the
pipes instead of all of it. This contention, however, carries
but little weight, and the disadvantage (for it certainly exists, as
can be noticed with any experimental apparatus) is so trifling
in actual practice as to be hardly appreciable (except at first
starting), not even with the squarest-topped boiler that is made.
This boiler is usually fixed upon and connected with
water-bars of a shape to permit of the stoking tools passing
under the lower edge of the boiler, which could not be done
with the ordinary flat bars in this instance (see Fig. 140).

2 JO

Warming Buildings by Hot Water.

Fig. 140* illustrates a special form of tubular boiler which
has seen a deal of service, and is still in regular demand.
The illustration clearly shows the construction of this, render-
ing much description superfluous.

Fig. 140.

This description of boiler is always arranged for top
feeding, the conical shape making it very suited for this, as
there can be no great risk of the charge of fuel " bridging "
up, instead of gradually sinking as the lower part burns away.

* From the catalogue of Messrs. J. Weeks and Co., of Chelsea, London.

Boilers for Brick Setting. 21 1

The conical shape, however, has its chief use in increasing
results by overhanging the fire, the arrangement of the tubes
being such (as to spaces between them, &c.) that they receive
efficient contact with all heated products. Most of these
boilers, particularly those of smaller size, are made differently
to the one illustrated, in the fact that they do not consist of
two distinct halves as this one does ; this division, however,
only being for convenience of transport and passage into
cramped positions.

The illustration shows the boiler set on to and connected
with water-bars, the dipped shape of these latter being
necessary to admit of stoking, which could not be readily
done otherwise. The return pipe is shown brought into the
water-bars as is customary.

The setting of this boiler is effected by enclosing the boiler
in a circular surrounding of brickwork corresponding with the
shape of the boiler, but a little larger, the top being finished
off flat with the feeding door in it, and the chimney being
carried off as near the top as possible, with a feather placed
to prevent the too direct escape of heat.

This description of boiler can also be had of saddle and
horizontal square shape, but the upright conical shape has the
most favour. With ordinary care they are very lasting ; the
makers' list offers a guarantee for ten years. It is a cast-iron
boiler.

This shape, and all boilers of a circular form, are best
cleaned out with a chain. A wire is first passed round, and
once this is got through, the chain can easily be made to
follow.

Fig. 141* illustrates about the most powerful form of
boiler that has yet been made for hot-water circulation. This
should have been classified with the independent boilers, as
it is wholly independent of brick-setting, but it is very much
removed in both size and character from the independent

* " The Python." From the catalogue of Mr. James Keith, Holborn
Viaduct, London. This boiler is so named, as it can be lengthened or
contracted by increasing or decreasing the number of sections.

P 2

212

Warming Buildings by Hot Water.

Boilers for Brick Setting. 213

kind, and it should be surrounded with brickwork, or some
low conducting material, to prevent the great loss of heat that
would otherwise occur, as the boiler is water-jacketed every-
where except the front*

It will be noticed that the particular object aimed at with
this boiler is to get the utmost possible direct and semi-direct
heating surface, and by this means to render the boiler practi-
cally independent of the (comparatively) little additional help
it would obtain from outer flue surfaces. This end, it is
needless to add, is fully attained in the boiler illustrated ; but
if it were not that it had been made and subjected to con-
siderable use for some time, the apparent complexity of its
construction would suggest caution in speaking of it ; in this
case, however, the boiler has had every test possible, and
has come out successful. The troublesome features which a
boiler of this kind introduces to its manufacturer are, firstly, the
mathematically correct allowance necessary for expansion
and contraction (for a very little variation in temperature
would show results with the long tubes of this boiler), an
allowance which needs the utmost care in a large boiler, and
particularly in a cast-iron one (as this is), which has such
rigid surfaces. Secondly, there must be a simple means of
cleaning it from soot or dirt, which so quickly decreases the
value of the heating surface ; and there must also be, very
importantly, a means of cleaning dirt and incrusted deposit
from its interior.!

* There are but two flow pipes shown on this drawing : it would be
better were there three or four, as such a rapid heater should have every
provision for its water to pass off rapidly. All large boilers should have two
or three flows, or (if particularly convenient) one or two of larger size.
One flow is not usually sufficient for a rapid heating boiler of any size.

t It may be mentioned that a boiler like this, heating perhaps up-
wards of 10,000 feet of pipe, must cause a deal of water to be evaporated,
which, of course, necessitates the introduction of fresh water, and adds to
the hard lime deposit ; so provision must be made not only for flushing,
but also for scraping out, as although an " anti-incrustator " fluid would be
used with a boiler like this, the deposit in its loosened state would still
have to be removed. If the boiler was used for heating water for sup-
plying public baths, c., then the question of incrusted deposit would be
a serious one.

214 Warming Buildings by Hot Water.

This boiler has provision made for both of these last-
named works, and its sections are also ribbed outside, so as to
permit of the ready application of any boiler-coating com-
pound to prevent loss of heat. The metal of the tubes is
about f inch thick.

The automatic damper in connection with the chimney is
an ingenious arrangement, much upon the principle of an
Arnott's ventilator, as it can be set to work with any strength
of draught. Its action is brought about by the fact that the
up-current of air in a chimney is due to difference in gravity
or weight between the outer cool air and the heated air in the
flue, the latter being made to ascend by the pressure exerted
by the superior weight of the latter (see Chimneys). Now this
pressure is, in the usual way, only exerted at the lower end of
the chimney through the fire-box ; but if we cut a hole in the
flue somewhere a little way above the stove, we shall find that
the cold air will instantly push itself (so to speak) in the
aperture with a deal of force, so that if we fixed a balanced
door at this point, the outer cold air would have sufficient
force to make it swing open to give it entrance, and the
stronger the draught in the chimney, the greater force the
outer air will exert in entering (by reason of a greater volume
being required in the chimney), causing the door to open
wider ; and the weaker the draught, the less the inflow of air,
and the door will incline to swing shut proportionately with
the feebleness of the current of air passing in. The particular
utility of this valve is that when the fire is out or low, the
draught is at its least, and the door remains shut ; but if the
fire becomes fierce (through inattention), the draught by the
great heat evolved becomes stronger, and the door gradually
swings open, \ permitting air to enter the chimney without
passing through the fire, thus checking and decreasing the
passage of air through this latter direction, and so automati-
cally regulating the speed of combustion, as the combustion
is wholly controlled by the strength of the draught through
the fire. This valve, in fact, acts as a governor, and it can be
" set " so as to permit of a certain speed of combustion being

Boilers for Brick Setting. 215

attained before it opens. The Arnott's valve is of particular
use when fixed in a kitchen chimney breast, as it will
automatically regulate the working of the kitchen range,
instead of its regulation being dependent upon the partial
closing of the dampers, which is never done.

There remains one more boiler to be noticed, as it has
done enormous and long service, and in many cases is now
found advantageous in use, notwithstanding the variety of
new patterns designed since its introduction. This is the
Trentham or Cornish boiler, Figs. 142 and 143,* elevation and
longitudinal section. The large amount of room this neces-
sarily occupies is an objection sometimes, but for many years
it was considered very economical in fuel, and this doubtless

Fig. 142.

has prolonged its use ; but it is doubtful whether, with all its
years of useful service, it will be in demand much longer, as
its economical features are now outdone by several of the
newer patterns.

This boiler is very commonly fitted with cross tubes,
behind the fire box ; and immediately behind where the fuel
rests there is provided a " bridge," a raised part which causes
the flame and heated gases to impinge upon the upper surface
inside. The sectional drawing shows the boiler as having a
waterway check end, which again adds to the total effective-
ness, as has been explained. The flame is, after it leaves the
interior, conducted by means of flues to and fro the length of
* From the catalogue of Messrs. R. Jenkins and Co., of Rotherham.

2 1 6 Warming Buildings by Hot Water.

the boiler, some engineers preferring to first carry the flames
under the boiler, and then to pass along the top to the
chimney ; others first carry the flame over the top of the
boiler, and then along the bottom to the chimney, much
in the same way as explained with the saddle boiler. Each
has an argument in favour of its respective way, but in
actual results, there is not the least doubt, for the reasons

Fig- 143-

several times mentioned, that the former method is best.
There are sweeping doors for the flue ways at top and bottom
of the fire front, as shown in both cuts.

This is another boiler that should have two or more flow
pipes leading away from it ; it is of too large a character to
have all its water pass away up one pipe, unless it was of
large size.

CHAPTER X.

APPLIANCES AND FITTINGS FOR HORTICULTURAL WORKS.

Hot-water pipes and fittings Price list Jointing pipes The rust joint
Red and white lead joint Rubber ring joint Improved expansion
and other joints Stop valves and their uses The throttle valve
The .slide valve The medium screw valve The reliance valve-
Furnace fittings.

A PECULIAR source of annoyance and trouble occurs with
ordinary cast hot-water pipes, by reason of the varying thick-
ness of the substance of metal in the castings, and the differ-
ence is particularly noticeable between pipes and fittings, the
former almost invariably being lighter or less in substance
than the latter ; and it is to be presumed that either the
moulders at the foundry are paid differently for pipes than
for fittings such as paying by the piece for pipe and by
weight for fittings or it is a sign of careless work in the mould-
ing shop and a proportionate waste of material, as nothing
is gained by the fittings carrying this surplus metal, and it is
a constant source of trouble by reason of the work it occa-
sions in making joints. Sometimes there is a f-inch space for
the joining material, sometimes the spigot end of the pipe will
only just pass into the socket, and this is particularly unfor-
tunate with the rubber ring joints, as will be learnt directly.

Another ill practice that has become a little prevalent is
that of issuing pipe insufficient in diameter and weight No
doubt it is brought about by competition, and it never need
be feared with any firm of good standing. A 9-foot length of
4-inch pipe should weigh 98 Ibs.,* and its size, 4 inches, is
internal diameter in the pipe portion (not in the socket).

This pipe differs considerably to cast smoke pipe and to
* See Appendix.

2 1 8 Warming Buildings by Hot Water.

the pipe used so extensively for conveying the rain water
from roof gutters to the ground, both these latter being of a
much lighter quality ; and, as a rule, the pipe for hot water is
cast from different metal of a somewhat finer quality. Nearly
every make of hot-water pipe has two or three (usually three
to a 9-foot length) bands or rings cast round the diameter of the
pipe, one at the opposite extremity to the socket, and two at
equal distances between. The socket is considerably larger than
the pipe (compared to the other two qualities of pipe men-
tioned), so as to admit the ringed spigot end and give suffi-
cient room for the jointing material and the tool with which
it is caulked. It has no flanges for securing it to wood or
brickwork like the rain-water pipe. The socket should be
particularly strong, with two cast rings formed round it and
with strengthening bars between them. The different varieties
of patent joints, expansive and other kinds, will not, of course,
be found to answer to this description correctly, but they
should be equal in strength and quality.

The following list comprises all the fittings in general
demand, and is compiled from the catalogue of a well-known
firm, and the prices shown may be considered as the average
cost of these goods of a satisfactory quality.

PRICED AND DESCRIPTIVE LIST OF HOT-WATER PIPES AND FITTINGS OF
THE ORDINARY KIND.

(These prices are subject to a discount to the trade.)

Hot-water pipe, 9 ft. lengths

6ft.

3ft-

spigot or coil pipes, 3 ft. 6 in. to 7 ft

2 ft. to 3 ft.
,, ,, 6 ft. to 9 ft.

Trough pipes, 9 ft. lengths, troughs 4 in. wide
6 in.

9 in -

Loose trough, 2 ft. 6 in., to fit on pipe
Evaporating trough, 6 ft. x 15 in. X 7 in. deep.

2 in. 3 in. 4 in.

2/ 2/6 per yd.

1/4 2/ 2/6

1/6 2/2 2/8

1/4 .-
1/6

2/ 2/6

3/8 5/6 6/6

6/9 8/

8/6 10/4

2/10 3/6 4/8 each.

Appliances and Fittings for Horticultural Works. 219

No.

2 in.

3 in-

4 in.

Elbow, i socket,

ist row

1/6

2/5

3/o

each.

2nd

2/8

3/8

4/6

7rd

6/4

8/0

4th

/ T^

10/9

cth

IO/4

2 sockets,

ist

}}

1/9

* / *T

2/9

3/7

2nd

3/10

4/9

3rd

6/8

8/8

4th

8/6

1 1/

10.

cth

10/7

14/7

ii.

,, no sockets,

ist

1/6

2/5

TV O

12.

2nd

2/8

3/8

4/6

17.

3rd

6/4

14.

4th

/ T^

IO/Q

9 9

15.

{-111.

Cth

10/4

/ s

9 9

1 6.

|th circle, I socket,

1st row ..

1/9

3/2

J 7-

> 9

2nd .. ..

2/3

3/7

4/9

18.

3rd .. ..

6/4

19.

4th .. ..

10/9

20.

5th .. ..

10/4

I4/

21.

,, ,, 2 sockets,

ist ,

3/4

. 4/4

22.

2nd .. ..

3/2

4/9

5/8

23-

3rd .. ..

6/7

8/3

24.

4th ,,

8/3

1 1/

25-

5th .. .,

10/7

H/3

26.

|th angle,

I socket,

ist .. ..

2/3

3/4

4/6

27.

2nd .. ..

3/3

4/4

5/6

28.

reducing,

4 *

3 in-

ist ,

3/w

' 99

2 9 .

4 X

3 9,

2nd

5/8

30.

4 X

2 ,,

ist ,, .. ..

3/ic

1 >

31-

4 X

2 ,,

2nd .. ..

5/8

32.

3 X

ist .. ..

33-

3 X

2 ,,

2nd .. ..

34-

> j

3 X

4 99

ist .. ..

3/*o

35-

j x

4 99

2nd .. ..

5/8

36.

2 X

4 ,1

1st ,,

3/10

37-

2 X

4 ii

2nd .. ..

5/8

38.

2 X

3 99

ist ,

39-

2 X

2nd ,

40.

Offset

, i socket,

3 in

. projection

2/IO

4/6

41.

> 9

2/10

4/8

6/4

42.

3/6

5/4

6/8

43-

3/6

5/4

6/8

44.

,, ,, 12 ,,

7/3

45-

2 sockets,

2/10

4/6

46.

2/10

4/8

6/4

47-

3/6

5/4

6/8

22O Warming Buildings by Hot Water.

No,

2 in.

3 in.

4 in.

48.

Offset, twin, I socket

3/8

7/6

49-

3/8

7/6

50.

,, ,, 2 sockets

4/4

6/6

8/6

51.

95 55 55 '

4/4

6/6

8/6

52-

,, reducing, 12 in. projection, 4 x 3 in.

53-

4X3

7/6

54-

5, ,9 4X2

55-

99 99 ,9 4X2 ,,

7/6

56.

59 99 9> 3X2 ,,

57-

99 99 9> 3X2 ,,

5/8

58.

Syphon, open 2 way

2/3

3/8

4/6

59-

,, close 2 ,,

2/3

3/8

4/6

60.

7 ,

4/6

7/8

9/10

61.

99 99 499

9/10

13/6

62.

7/3

1 1/9

1 6/3

63.

8/6

13/6

1 8/6

64.

,, elbow, spigot outlet, 2 sockets ..

65.

99 9 9> 3 99 ....

12/6

66.

4 99

12/6

1 6/6

67.

5 9, .. ..

8/6

13/9

i8/

68.

99 99 9J ^99 ....

9/9

15/3

19/9

69.

,, ,, socket outlet, 3

3/10

7o.

4 9, "

12/6

71.

5 ,9 - "

12/6

1 6/6

72.

99 99 9. 6 ,,

8/6

13/9

i8/

73-

7 99

9/9

15/3

19/9

74-

,, ,, reducing, 4 X 3 in. spigot out.

75-

99 99 99 4X3 99 99

12/6

76.

4 X 2

12/6

77-

,,4X2 ,,

16/3

78.

,, ,, ,, 4x2 ,, socket out.

8/3

79-

,, 4 X 2

16/3

80.

outlet, open, 2 way, spigot outlet ..

3/10

7/IO

82.

,, ,, close, 2 ,, spigot ,,

83.

9 /

12 j 6

84.

12/6

1 6/6

8/3

1 8/3

86.

,9 99 99 6 ,,

9/6

15/6

/ O

20/

87.

,, ,, ,, 2 ,, socket outlet ..

-7/

88.

59 99 19 3 99 99 91

12/6

89.

99 4 99 99 99

12/6

1 6/6

QO.

8/3

I4/

1 8/3

.7 V

91.

,9 99 6 ..

/ O

9/6

15/6

/ J

20/

92.

,, ,, 4X3 in. reducing

07.

91 99 4X2,, ,,

94.

99 99 3X2,, ,, ..

each.

Appliances and Fittings for Horticultural Works. 221

No.

95-

96.

97-
98.
99.

100.
IOI.
102.
103.

104.
105.

106.
107.
1 08.
109.

I IO.

Syphon, branch, 2 way, socket outlet
i 2 spigot outlet .. ..
i 11 3 11
4 , 11 " "
i 11 5 11
6 ,, ,, .. ..
, ,, 2 ,, socket outlet ..
i 11 3 11 11
i 11 4 11 11
i 11 5 11 ....
6 .. ..
, chair, spigot outlet
, ,, socket ,,
, coil, 2 way, spigots

i 11 Z 11 11
H piece, close . . . .

2 in.
3/9
3/9

6/
7/
8/6

9/9
3/9
6/
7/
8/6

9/9

4/
3/6
4/6
5/

3 in.

6/
9/

12/6

14/6
1 6/6
6/
9/

12/6

14/6
1 6/6

6/3
6/6

6/
7/8
7/8

4 in.
8/
8/

12/8

16/9

iS/3
20/9

12/8

16/9

18/3
20/9

8/2

8/8
8/
1 1/

10/4

each.

11
11

open

7/8

IO/4

112.
117.

Cross piece, 2 sockets

4/2

6/4
7/

8/6
9/6

114.

to
151.

1^2

>Tee piece, equal and reducing
Branch piece

2/3
4/

3/8
5/9

4/6

7/4

1C -I.

4 /

C/Q

7/4

ic/i

Reducing nipple 4x3 in

2/7

ice

4x2,,

2/3

itfi

7X2,,

1/8

157-
158.

159.
160.
161.

162.
167

,, piece, 4 in. spigot, 3 in. socket ..

11 11 4 11 2 ,,
3 11 2

11 11 3 11 4 11

11 > 2 ,, 4 11
11 2 ,,3
7 X A ill

2/8
2/8

3/6
3/6

7/6

1 6 A

2X4.

7/6

1U 4-

165.

1 66

> 2x3**
Blank spigot

2/8

1 66

cored

1/7

167.
167.
1 68.
1 60

,, socket or cap
cored
Union socket or collar

1/2

1/8

1/6
1/6

2/8

2/
2/3
2/

3/8

I7O

2/3

3/4

4/4

171

socket

2/6

3 /

1/1.
172

2/7

3/4

4/6

I /A

I 77

2/7

3/4

4/6

1 /J'
174.

175-

Flange and socket elbow, short
long

3/2

3/4

4/3

4/6

5/6
5/6

11
11

222 Warming Buildings by Hot Water.

No.
176.
177.
178.
182.
183.
184.
185.
1 86.
187.
1 88.
189.
190.

Socket for welded boiler
,, over end
,, overside
Throttle valve, socket, and spigot
,, ,, 2 sockets
H pipe valve, open, I valve
,, ,, ,, 2 ,,

2 in.
.. 3/4
.. 3/9
.. 3/6
.. ii/
.. ii/

-. 2 5 /
.. 28/6

3 in.

4/6

4/9
4/6

I3/
I3/
3o/
35/8
BO/
30/
35/8
So/
34/
34/

2O/
20/
20/
20/
27/
27/

/5
/5
2/
i/

4 in.
5/8 e;
5/9
5/6
IS/
IS/
35/
42/8

54/
35/
42/8

54/
4i/
4i/
*5/

25/
25/
25/

3o/
3o/

2/6

'/3

ich.
i

i
>
i
i

n
11

>}
)>
)>
> >
>
7)

43/

,, ,, close, i ,,
,, ,, ,, 2 ,,

.. 2 S /

28/6

,, ,, ,, 3 ,,

43/

T ,, .. 2

.. 28/
.. 28/

.. i6/
.. i6/
.. i6/
.. i6/
.. 2 5 /

.. 2 S /

191.
198.
199.
200.

201.
202.
203.

2 ,,

Diaphragm valve, socket and spigot ..
,, ,, 2 sockets
,, ,, angle socket and spigot
,, ,, ,, 2 sockets
Slide valve, 2 sockets
,, socket and spigot
Pipe stands, single

,, double
Caulking tools, steel
,, iron
Indiarubber rings
White and tarred yarn
Iron borings . .

/4
.. 1/6

/9
5/ per lb.

/S
9/ per cwt

There are several ways of jointing this ordinary descrip-
tion of socket and spigot hot-water pipe, almost every hot-
water fitter having some special notion of his own as to
quantity or the admixture of material, &c., but in general prac-
tice it will be found that the methods are confined to three, viz.
the iron borings or rust joint, white and red lead, and the
rubber ring. With the two former, hemp, yarn, or gaskin
requires to be used with the materials named, but the latter
is commonly used by itself. It will be understood that
although these joints have to be water-tight, they have but a
trifling pressure to withstand in glass-house work, very diffe-
rent to what the pipe joints experience in a building that
has several floors heated from one boiler. It is quite possible
to make a sound and lasting joint, where the pressure is so
low, with the yarn only.

The cheapest joint is that made with iron borings, as the

GENERAL IRON FOUNDRY CO.'S CASTINGS-HOT-WATER PIPE

CONNECTIONS

163 157 160 154-

84- 89

GENERAL IRON FOUNDRY'S CASTINGS-HOT-WATER PIPE CONNECTIONS

MACFARLANE'S CASH N G S H OT- WATER P'l P E CONNECTIONS

BM3

MACFARLANE'S CASTINGS HOT-WATER PIPE CONNECTIONS

Appliances and Fittings for Horticidtural Works. 223

material costs so little ; but in many respects this joint is
objectionable, as will be explained. The joint is made by
mixing with iron borings (which require to be pounded if
very coarse) some sal-ammoniac and sulphur, both in a
powdered form, these two latter materials bringing about a
chemical change in the borings, causing them to set hard and
solid, or, in simple language, causing the borings that are
driven into the socket joint to rust up into a solid mass.

This rusting process takes place slowly, or rather, it is
some time before the chemical action quite ceases, although
the joint may be quite rigid in a short time ; but as the change
that takes place brings about an expansive force, it is very
necessary that this joint be made skilfully, or the sockets
may be split. It is fair evidence of a man's good workman-
ship if his iron joints are made soundly, yet do not afterwards
split open, for it is no exaggeration to say that many
thousands of lengths of pipe have perished from this cause.

Some workmen consider that it is proper to first caulk the
joint half full of yarn, the remaining half with borings ; others
say three-fourths of yarn, and finish ofT with a fourth (about
f inch) of borings. Occasionally only half an inch of the
joint is of this latter material, and sometimes a joint may be
met with having first about one-third yarn, then half an inch
of borings, then a little more yarn, and finishing off with more
borings. There is no doubt that three-fourths yarn and one-
fourth borings makes a sufficiently sound joint under ordinary
conditions, but it would be better to make one-third borings
the least quantity,* although the less the quantity of this
material, the less the liability of the socket being afterwards
fractured. The borings once prepared cannot be kept except
for a very short time, as they set hard quickly.

This joint costs the least in materials, and is generally

* There is no doubt that the yarn by itself makes these joints water-
tight, the borings only acting as a support to the yarn, or to keep it sound
and the pipe rigid. The writer once saw some joints made with old rope
material caulked in, and when, in experiment, it was subjected to 30 Ibs.
pressure per square inch, it was perfectly sound, and had ultimately to be
burnt out before the pipes could be separated.

224 Warming Biiildings by Hot Water.

considered the cheapest in the end ; but when we take into
consideration the time occupied, the cracked sockets (which,
of course, ruins the whole length of pipe), the inability to
afterwards disjoint the pipe for alteration or repairs, &c., it is
doubtful whether the rubber ring does not run it very close
in ultimate expense. The proportions usually laid down for
making the rust joint are, by weight, one part powdered sal-
ammoniac, two parts powdered (flour) sulphur, and 80 to 100
parts borings ; thus I cwt. of borings would require about
2 J Ibs. of sulphur and fully I Ib. sal-ammoniac, and the whole
must be moistened and thoroughly well mixed. These pro-
portions are not fixed with any exactness ; if they vary a
little no harm results. In fact, when the mixing is left to a
workman, he judges (from previous experience) what is
needed, and puts, say, a handful of one material to so much
of another, calculating the aggregate amount by pailfuls very
commonly; but if too strong, a fracture may ensue, but if a
little too weak, it only takes a little longer in setting. It
requires to be made from half an hour to two hours before use,
according to the weather, and it usually cannot be kept
longer than one day without becoming hard.

The joint for general purposes, and which has the greatest
use at present, is that made with white and red lead and
yarn,* this being more simply made than the last, safe in
results, not so very hard and rigid, and there is no after-
action to endanger the sockets ; but the materials are a little
more expensive that the rust joint.

In making this, the white lead, which is a soft, sticky mass,
is mixed with sufficient dry red lead to make a mixture of
about the substance of putty when they are incorporated
together. It is then desirable to mix some of this material
with boiled oil to form a thick liquid paint to coat the socket
and spigot with before the jointing material is inserted ; next
a length of yarn is well caulked in, then a layer of the lead
mixture is introduced, then another length of yarn, and so on,

* It should have been mentioned that the yarn is readily procurable
adapted for this purpose ; it is used in pieces about a yard long.

Appliances and Fittings for Horticultural Works. 225

until the socket is filled, finishing off with the lead. This,
when dry, is a very hard and durable joint, and at present is
much in favour. It is the material just mentioned that is
used, with a little loose yarn, to make the joint where the
flanged socket is secured to the boiler.

The next joint to be spoken of is that which consists
merely of an indiarubber ring, the rubber being circular in
section, so that when stretched over a pipe it can be made to
roll up and down with moderate ease. This joint is made
by stretching the rings on to the extreme spigot end of one
pipe, then forcing it into the socket of the next, this being
sufficient to make a water-tight and sound connection, as the
rubber is of a proper thickness (about J inch) to effect this.
If, however, the castings are of irregular size, as just explained,
it frequently happens that the space left in the socket is
insufficient for the ring to pass in, even if the edge of the
socket is chipped round, and great force is used in the
endeavour to insert it. This is a drawback to the use of the
rubber ring joint, but fortunately not a serious one. Oftentimes
the space within the socket is just sufficient to admit the spigot
and ring upon it if great force is used, in which case the ring is
flattened out and makes a joint of decidedly sound character,
but one that would be difficult to undo after a little time.

The chief objection to this rubber ring joint is its utter
want of rigidity, as it affords no support whatever to the pipe,
and some form of bracket or pipe-stand is needed almost at
every length, unless the pipe happens to be laid on a flat
surface, or in a trench. But notwithstanding this, the joint is
a very convenient one ; it is durable, for the rubber adheres
to the metal after a time, and it is easily and very quickly
made. It is the kind of joint provided with the small
independent boilers that are sold with pipes complete for
erection by an amateur in his own greenhouse.

This joint does away with the necessity for any device
providing for expansion, as every joint in the whole apparatus
is a provision in itself. The cost of material (the rubber) is
more than that for a rust joint, but the greatly lessened time

226 Warming Buildings by Hot Water.

and the utter absence of risk equalises the ultimate expense
in each case. Many engineers are using the ring entirely
now, as, provided they have a careful foreman, only indifferent
labour is needed for joint-making.
Fig- 144. When there are a large number of

joints to be made, a " ring expander "
is used, as Fig. 144; the rings can
then be rolled on, which is better than
stretching them on with the fingers
an awkward method, causing the rubber to get twisted.

It is almost needless to add that there are other methods
of jointing pipes, by patent cements, &c., but the ordinary
and successful methods are all that can be safely spoken of.
As already mentioned, old rope, untwisted, will make a better
joint than yarn ; and there is not the least doubt that tarred
rope, old tarred scaffold cord, &c., would, under ordinary
circumstances, make a good joint by itself.

The particular and valuable use of a reliable expansive
joint as we get with a rubber ring, or one of those about to be
mentioned, is that with the fluctuations of temperature that
are constantly taking place to a greater or less degree, we get
a constant, though almost imperceptible, movement of the
pipes, sufficient to ruin any rigid joint in a comparatively
short time if the run of pipes be anything but short. We
have to remember that the flow and the return pipes are
never of an equal temperature, and that the movements or
strains brought about by the variations in heat are irregular,
and tend to make these pipes, which are connected at both
extremities, injure one another, as they do not act in unison
either as to time or extent.

In arranging to obviate this ever-present trouble, different
engineers have again different ways of proceeding. One large
firm of growers * that the writer came in contact with would not

* Large horticultural establishments always keep their own staff of
fitters, under a foreman engineer ; and there is ample work for several men
at many such places, when there may be perhaps fifty boilers in use, with
miles of piping.

Appliances and Fittings for Horticultural Works. 227

permit of a rust joint being made on their premises ; their
joints were made, some with red and white lead, and some with
rubber ring, a rubber ring at about every sixth joint as a pro-
vision for irregular expansion, as explained.* Another firm
preferred to use both red and white lead and rust joints, one of
each alternately, and this, of course, was satisfactory ; but long
loose sockets were provided, packed and arranged as stuffing
boxes, to allow the pipes to have a slight movement in them
as they expanded lengthwise. Great care has to be exercised
in this matter if three or four pipes are carried one above the
other, connected at their extremities, and are likely to be of
different temperatures.

An excellent form of patented expansion joint is as
illustrated, Fig. 145-t This consists of two cast collars, an

Fig. 145-

IMPROVED

OF JOINT

iron ring, and two rubber bands, the drawing together of the
two cast collars compressing the rubber, and effecting a very
sound joint. The particular advantage of this joint is the
fact that it is used with perfectly plain pipes, no sockets
being needed, nor need the pipe ends be perfectly regular
or cleanly cut. In addition to this, as the pipe is inde-
pendent of sockets or special ends, there is no occasion
to order or wait for certain lengths, as the plain pipe can be
readily cut and inserted at once ; and lastly, but of great
importance, this joint permits of any length being taken out

* If the expansion in both pipes was equal, expansive joints would not
always be needed, as the roller bearings to the supports would give freedom
of movement ; but even this would not suffice always, as the extension of
a long length of pipe might injure the branch services from it.

t From the catalogue of Messrs. Jones and Attwood, of Stourbridge
the patentees.

Q 2

228 Warming Buildings by Hot Water,

for repair, or in case of leakage, &c., almost instantaneously,
without disturbing any other parts of the service no mean
advantage, as any one will acknowledge, if, after laying down
a long length of the ordinary pipe, a bad leakage is found
somewhere about the middle.*

This joint is not by any means a costly one, and its
expense is somewhat lessened in the time saved in jointing
pipes and the non-use of jointing materials ; it can be used by
inexperienced persons, facilitates alterations, and the pipe is
of a little less cost than the socketed variety. The price of
a joint for 4-inch pipe, complete with bolts and rubbers, is
is. $d. (gross) ; they are made in all sizes from ij to 6 inches,
and can be had for reducing, or for receiving small wrought pipe
at right angles, or set to obtuse angles, and also attached to
throttle valves, &c. A well-known firm in Manchester uses
this joint extensively in small size for jointing copper pipes
in hot-water supply apparatus, and they are of the greatest

value for this purpose, as it is
Fig ' I46 ' so very difficult to get any metal

or rigid joint to last with copper
pipe that is subjected to heat.

Another expansion joint is
as Fig. I46.f With this one end
only of the pipe is plain, the
other end socketed in a special
form, one rubber only being

needed to effect the joint. The explanation devoted to the
last description will show what advantages this one possesses.
Another joint (Fisher's patent) is as Figs. 147 and 1484
This is used with plain pipe, no sockets or special ends being
needed, and the joint is made with red and white lead with

* Loose sockets have to be provided at regular distances, in long
lengths of pipe, jointed in the ordinary way. These act as unions, and
can be moved to disjoint the service.

f From the catalogue of Messrs. Newton, Chambers, & Co., of
ThornclifTe, near Sheffield, and London.

\ Also from Messrs. Newton, Chambers, & Co.'s catalogue. This
cannot be called an expansion joint.

Appliances and Fittings for Horticultural Works. 229

hemp, a strip of canvas being used to prevent any jointing
material entering the pipes. The two half-circular pieces are
corrugated inside so as to ensure the joint being made
soundly, by keeping the jointing material from being squeezed

Fig. 147.

Fig. 148.

out In making the joint the material is first spread on as
evenly as possible, and after the two sections are in position,
the key is driven up as shown ; but in doing this, care must be
exercised to see that in driving the key home the whole joint
is not shifted.

STOP COCKS AND VALVES.

In an earlier part of the book these two articles were
mentioned indiscriminately, without regard to whether the
circumstance made a valve or a cock desirable. It is now
time to explain the difference between the two, and to show
their respective uses.

The term " stop cock " is commonly used as applying to the
articles under discussion, but the term is really an incorrect
one, as a stop cock, in the proper sense of the word, is not
usually met with in this work : they are really all stop valves,
but of two kinds one the "throttle," and the other some
form of screw-down arrangement which shuts off the circula-
tion of water perfectly, which the throttle does not. Doubtless
the only cause which makes the throttle valve so much in

230 Warming Buildings by Hot Water.

demand is the fact that it is decidedly cheaper than the other
kinds, and as they operate with fair success with a slow
circulation such as we get in horticultural works, there is no
great objection to their use.

Fig. 149 illustrates a throttle valve, it being a short length
of pipe with a disc of metal within it operated by a handle, its
simple construction keeping the cost
low, an important consideration in
low-lying work, which will not always
permit of using valves of a smaller
"I l^^L_jn T|| size than the service pipe (as we can
== nr in heating buildings, which see) ;

(J I|J (Jl the cost of a moderately common

quality valve of a 4-inch size is as

much as 1 $s* In the ordinary throttle valve just illustrated,
the disc, which is turned in a lathe, is made to fit the opening
in which it works as closely as possible ; but it cannot be made
water-tight, as allowances have to be made for expansion of
metal, &c. No opportunity must be given for the working
parts to get bound up in any way, as these valves, when once
set to the requirements, may not be afterwards operated very
often, although, properly speaking, they should be looked to
and tried very frequently.

The fact that a throttle valve does not perfectly shut off
the circulation is not a very great objection in some horti-
cultural works, as just explained, for the circulation, although
it may be good in the ordinary sense of the word, is not very
rapid, consequently it is easily checked or stopped to such
an extent as to prevent any very noticeable movement past
the valve, and the water passes on in other directions freely,
as its impetus is not sufficient to force a great amount past an
obstacle. In a vertical apparatus, even of moderate height,
the circulation is of sufficient strength to effectually work
through a very small opening, which permits of the use of

* Occasionally valves of a smaller size than the service pipe can be
used, but rarely with extensive works in glass houses, where the motive
power is low.

Appliances and Fittings for Horticultural Works. 231

small pipes between the boiler and the radiating media, and
also small valves, without impairing results, in the usual way.

The use of throttle or perfect valves is another question
generally decided by the gardener in horticultural works, and
their use is greatly governed by what is to be stocked in the
houses, some gardeners contending that a slight variation or
irregularity in temperature is sufficient to interfere with the
steady progress of the plants. When such care as this is
needed, the gardeners will not admit a throttle valve of any
description.

Fig. 150* shows a throttle valve similar to that just
described, but having facilities for removing the disc or
working portion for repairs, or for easing
the working parts when too stiff, &c. This Fi s- r 5-

is a decided improvement, as these valves
of the ordinary description are far from
simple to get at when attention is needed ;
whereas this one, as the illustration plainly
shows, renders the matter exceedingly
easy. This valve, as well as the one last
explained, has a stuffing box at the point
where the rod of the handle passes through
the substance of the pipe. Without this, of
course, it would be difficult to make it water-tight, and the
stuffing box is also required to make the valve work steadily ;
in fact, it is usual to have them work rather stiffly, so that
there may be no risk of the disc moving from any slight cause
after it has been set by the gardener.

Fig. 1 5 1 t illustrates what is commonly called a slide
valve. This is a valve of the " perfect " kind, which does not
permit of the water circulating past it when it is closed. In
the illustration it will be noticed that the circulation through
the barrel of the valve is checked or cut off by a slide or door,
which is caused to move downwards by the screwing down of

* From the catalogue of Mr. W. G. Cannon, heating engineer, London
Road, London.

t Also from Mr. Cannon's catalogue.

(Of

232 Warming Buildings by Hot Water.

the wheel handle (the valve is, of course, opened by reversing
the motion). This permits of the movement in the water being
regulated to the greatest nicety, and the gardeners who require

Fig. 151.

great exactness in results, are able to get it with a valve of
this character. This valve is used to a very considerable
extent.

Fig. 152,* the medium screw valve, shuts off the circula-
tion perfectly (even more perfectly than the last, which could
not be considered thoroughly water-tight, although it effec-
tually stops the circulation). This is a screw-down valve, the
seating being turned and faced with rubber. It is a simple
yet effective valve, but one which has a clear straight way
through it is preferable.

Fig. 152.

Fig 153-

Fig. 1 53 is another valve of the " perfect " kind, its working
parts beL;g a disc hinged at the top edge with a turned face,
* Also from Mr. W. 'G. Cannon's catalogue.

Appliances and Fittings for Horticultural Works. 233

or faced with rubber, the opening and closing of this disc
seating being effected by an ingenious thread and tooth gear,
as shown. This has a straight passage through it, but it
requires to be mentioned that all valves faced with rubber
should have fairly constant use, or the seating will adhere
to the metal it presses against if left closed, this result being
accelerated by heat.

The last that needs mentioning is as Fig. 154,* a novel
arrangement, effecting a considerable saving in H and T

Fig- 154-

pieces, which very usually require two and three valves each
to do what this does with one. It is in reality a double or
treble-acting throttle valve, the disc being replaced with
two leaves placed at right angles or in a line, as shown.
With the T valve a quarter turn of the handle sends the
water in either direction, but it can be placed so as to permit
circulation in all directions if required. With the H valve
the action is different, a quarter turn of the handle permitting
the water to either pass along the flow and return past the
valve (as illustrated), or, on the other hand, causing it to pass
from one pipe to another without passing the valve, thus
effecting precisely the result that three valves are required to
do in the ordinary H piece.

There are other forms of valves, more or less modifications
of those spoken of, but it is needless to describe them here,
as all that is required is to explain the different acting prin-
ciples of what are at present in demand. Undoubtedly the
ordinary throttle valve has the greatest use of all of them ;
but, as explained, it is to a great extent due to its lowness in

* " The Reliance Valves," from the catalogue of the Thames Bank Iron
Co., Upper Ground Street, London.

234 Warming Buildings by Hot Water.

price. Although it was pointed out that some gardeners
required the greatest exactness in temperature, even to one
degree of heat, this is only in cases where delicate things are
being reared, or some important feature is being developed.
To many of the common articles that come from glass-houses,
a little irregularity is not minded, as they may be tolerably
hardy, and only require to be guarded against the severe cold
of night or winter.

The throttle valve * has the advantage of a screw-down
valve in indicating by the position of the handle the extent
to which it is opened or closed. The screw-down arrange-
ment does not do this, and if in doubt, the attendant has to
try it by screwing the handle up or down to ascertain how
much it is opened or closed ; but when the screw-down valve
is in use, the gardener soon ascertains how many turns the
handle requires for the result he wishes to obtain. It may be
mentioned that valves are made to meet every requirement,
for corners, upright, in box-ends, &c.

None of the valves here mentioned are used for hot-water
works in buildings where smaller pipes are introduced between
the radiating media and the boiler. These will be referred to
when that subject is treated.

Although mentioned before, it will bear repeating, that it is
not sufficient to put a valve in the flow pipe only there
must be one in both flow and return, or the hot water will
find its way up the latter pipe, and produce very annoying
results. If throttle valves are used, it becomes, if possible,
even more necessary.

FURNACE FITTINGS.

The variety of these is very limited, and at present there
seems no demand for any extensive improvements. They do
not seem to create any particular feeling of competition, as the
same patterns can be got from nearly every maker, appearing,
with little exception, as if all were made from the same design.

* This valve has a very straight and full way through it.

Appliances and Fittings for Horticultural Works. 235

Fig. 155* shows the oldest form at present in use a cast frame,
with two cast doors with wrought hinges and fittings ; and
there should be a shield plate, properly affixed to the inner
side of the upper door, otherwise the heat will soon affect it.
This shield plate is shown on the door in section, at Fig. 109.
This plate should be cast iron, which is at all times better

Fig. 155. Fig. 156.

able to withstand heat than wrought, especially when no
medium, as water, for abstracting the heat exists. The upper
door of this style of furnace fitting is sometimes made circular
in shape an improvement and sometimes the front casting
is also circular at top.

A more modern fitting is as Fig. 156,1 a front casting with
an arrangement of rails upon which the doors are merely
hung, and can be pushed freely to the right or left, or as easily
lifted off. This does away with two rather weak features in
the other fitting, viz., the hinges and latches, which do not
operate well, that is, easily, to the attendant, who more often
uses his foot than an instrument to move the doors. This
sliding arrangement permits perhaps of more careful adjustment,
firstly, of the lower ashpit door, which is utilised as a damper,

* From the catalogue of Mr. W. G. Cannon, heating engineer, London
Road, London.

t Also from Mr. Cannon's catalogue.

236 Warming Buildings by Hot Water.

and of the upper door, which is sometimes opened slightly when
the gardener wishes to gradually cool down a little without
interfering with his fire. There is another form of sliding door,
which does not project so far as this one ; and it should be
mentioned that there has been a set of doors recently intro-
duced with the outer frame extended so as to include the

customary three soot doors in it,
as -pig. 157.* This is an improve-
ment, as the box soot doors
just inserted in the brickwork
will so commonly come loose by
friction with the flue-cleaning
tools ; but it must be noted that
the provision of soot doors in the
front casting rather fixes the
boiler setter with his flues.

The dumb plate should be
of what is called the new or im-
proved pattern, being rebated at
the edge where the bars come and rest upon it (see Fig. 109).
The older pattern was a plain flat plate, which butted against
the front edge of the bars, the two being supported by a
bearing bar, which was a source of trouble, being situated
where a most intense heat could act almost directly upon
it. A wrought bar would quickly get misshapen.

The furnace-bars (which can be spoken of but very
briefly, as it is a fit subject for a small book by itself) are very
usually of the plain fished or fish-belly shape. These should
be thin and deep to give the best service. Their chief enemy
is clinker, which adheres most tenaciously, and does its
best to stop up the spaces that intervene between the bars.
This objection is overcome to a very great extent by using some
one of the different pattern bars that are now made with
grooves or channels cut in their top surface, where the fuel
rests upon, the usefulness of these grooves being in the fact
that they become filled with ash, which protects the metal
* Also from Mr. Cannon's catalogue.

Appliances and Fittings for Horticultural Works. 237

surface, and ash being a poor conductor of heat, the life of
the bar is lengthened to a considerable extent. This is a
valuable improvement, but one which most of the readers
will be acquainted with, no doubt, as it is far from being new,
having been introduced for the furnaces of steam boilers
very many years ago.

Water bars, i. e. furnace-bars made of a row of tubes
having water circulating through them, have
been referred to on p. 198. Fi S-

The form of soot door most commonly
used is as Fig. 158, and is termed a box
soot door, by reason of its length. This is
the best form of door, the deep flange to
the frame giving it the utmost possible chance of being
securely fixed in the brickwork. The damper in the flue needs
no description, nor does the form of soot door that requires
to be placed in the chimney for sweeping purposes.

238 Warming Buildings by Hot Water

CHAPTER XL
QUANTITIES FOR HORTICULTURAL WORKS.

Hood's rule and its application Hood's calculating table and notes
thereon Rapid calculating table and notes thereon.

THE quantities mentioned in this chapter are of 4-inch pipe,
this being the most useful size, as a foot length can be con-
sidered a superficial foot of radiating surface, and therefore
the quantities in question will readily apply to radiators and
other irregular shaped articles, the radiating surface of which
the makers' lists give in superficial feet. If a smaller sized
pipe is used, the quantity used will be one-third more for
3-inch and double the quantity for 2-inch pipe.

Hood has laid down an exact rule which has needed
no variation in horticultural work, but which, owing to its
complexity, has had little use from the average engineer ;
but it has been from this rule that practically all others of a
simpler form (but approximate only) have been deduced.
This rule is as follows :

Rule. Multiply 125 by the difference between the tem-
perature at which the room is purposed to be kept, when at
its maximum, and the temperature of the external air, and
divide this product by the difference between the temperature
of the pipes and the proposed temperature of the room ; then
the quotient thus obtained, when multiplied by the number of
cubic feet of air to be warmed per minute, and this product
by 222, will give the number of feet in length of pipe, four
inches in diameter, which will produce the desired effect.

This rule is based upon the fact that every superficial foot
of glass which constitutes the glass house is capable of cooling
i \ cubic feet of warmed air down to the temperature of the

Quantities for Horticultural Works. 239

air on the outer side of it, per minute,* and the result given
by this rule is the quantity of 4-inch pipe needed to make
good this cooling influence, the calculation allowing for the
lowest possible night temperature outside, say 10 F. (22
below freezing), and the water in the pipes being about 180.
In allowing for so low a temperature as 10, it is supposed
that all ventilating appliances will be closed at this time, which
would be in the night ; ventilation only being allowed on a
small scale during the day, when the thermometer would
register 20 at its lowest. Of course, it is supposed that venti-
lation be almost dispensed with when these phenomenally
low temperatures are experienced.

According to this rule, a grape house requiring to be kept
at a temperature of 60, and having 1000 superficial feet of
glass to it, would require 293 feet of 4-inch pipe, as follows :
125 x 50 (difference between internal and external tem-
perature) = 6250 -f- 1 20 (difference between heat of pipes
and internal temperature) = 52 x 1250 (cubic feet of air
cooled by 1000 superficial feet of glass per minute) =
65,000 -f- 222 = 293 feet of 4-inch pipe to keep up a heat
of 60 in the house when the outer temperature is 10.

In arriving at the quantity of glass, the material of the
frames, &c., are included ; but if they be wood, one-eighth total
area can be allowed and deducted. For metal frames no de-
duction is permissible, as they as readily reduce the tempe-
rature as glass.

Hood points out that although wind is a most active
element in reducing temperature,! there is no need to take
it into consideration, as when an excessive degree of cold
is experienced, it is rarely, if ever, accompanied by wind ; and
consequently when wind in any strength manifests itself, the

* Corrugated iron, when existing, requires to be calculated, and have
the same allowance made for it, as glass.

t We can readily judge this by the difference in our feelings on a
windy day and a still day, although the thermometer registers the same
temperature on each occasion. Air is a poor conductor of heat, and when
it is still it does not permit of such a ready escape of heat as when it is
moving rapidly past the heated surface.

240 Warming Buildings by Hot Water.

thermometer will always be moderately high compared with
the degree of coldness this rule is based upon, viz. 10.

The rule in question permits of variation if the position in
which the house is situated should be very well sheltered, or
be in any part of England, or other country, where the tem-
perature does not fall so low as that mentioned ; and there
might be considered other features, such as whether the fire
will be attended to by a practical man or by an inexperienced
person, but for general horticultural works it may be considered
that the attendants are skilled.

Hood also points out, and goes to some lengths to
prove, that the glass, whether vertical or sloping (for both
appear in nearly every glass house), needs but the same
allowance in calculation. There is, as he shows, a difference
in the degree at which the heat may be abstracted ; but the
difference is unimportant, and as it would be governed by a
number of complex conditions, it is best to treat all the glass
at the same rate. But to be safe, the surface which loses heat the
fastest is taken as a standard, which is usually the vertical,
and this cools I J cubic feet per superficial foot per minute, as
already stated. There is also a difference between lapped
glass* and glass set in iron or wood frames ; but this difference
only exists if the internal air be dry, and this never being the
case in horticultural work, no allowance on this score is needed.

As before stated, Hood's rule, though mathematically
correct, is, we may say, never used : it is not adapted to the
understanding of many who undertake this work, and with
those who might be able to use it, something that permits of
more rapid calculations being made is better liked, notwith-
standing that the rapid calculating tables introduce a deal of
approximate and guess work.j This, however, is usually met
by allowing a little more pipe than the needful quantity, if it

* The majority of new work is carried out in this way, as all the new
systems of horticultural glazing allow for lapping one pane upon another,
with usually a complete absence of jointing material.

t Guess work is much too prevalent, and doubtless would account for
many failures. How many engineers are there who could confess to
taking measurements by sight only, without a rule or measuring tape !

Quantities for Horticultural Works. 241

is considered that the circumstances require it by reason of
exposed situation, &c.

The rapid tables are compiled by allowing a certain quan-
tity of pipe per thousand cubic feet capacity, the quantity
of pipe varying with the temperature required, so that if we
have a glass house 30 feet x 10 feet X 10 feet, we readily
find its cubical capacity is 3000 feet, and if we require a
temperature of 65 when the thermometer registers 10 out-
side, we must allow 55 feet of 4-inch pipe per 1000 cubic feet
capacity = 165 feet of pipe for the house in question. Nothing
could be quicker than this, but it is very unreliable, chiefly for
the reason that in twenty houses of the same cubic capacity,
probably not two would have exactly the same area of glass.*
As all authorities will agree, the area of glass controls the
results, and differences in results must consequently occur,
although, perhaps, in the majority of cases the variation may
not be important, and if the difference is sufficient to be
important, then it would be noticed and allowed for.f
Another feature making the capacity tables unreliable is
that if we have a house, say 20 feet long, and one 40 feet
long, both of the same width and height, we get in the second
double the cubic capacity of the first ; yet (assuming they are
both built to the same design) we do not get double the glass
surface : we should get double the top and side surfaces, but
the ends would remain the same, and as the ends represent
a moderately fair proportion of the whole, an inaccuracy of
some moment is introduced.}: In compiling the table for

* The difference in this respect between lean-to houses (against a
wall) and span houses is tremendous.

t It is the quantity of glass wholly and solely that regulates the
quantity of pipe required in horticultural work : when once the interior is
heated the heat may be said to be lost from the glass only. There is
practically nothing else to abstract the heat except ventilators, and the
gardeners do not look to bring these appliances into use during the bitterest
cold of winter midnight. At other times the heat given off will permit of
a little reduction.

\ In the same way a glass conservatory, which is very commonly
higher than a vinery, would get more than its proper share of pipe (which ,

242

Warming Buildings by Hot Water.

this method of rapid calculation (page 245) the writer has
only been able to base the figures upon the average quantity
of glass per 1000 cubic feet internal space.

TABLE SHOWING THE QUANTITY OF 4-iNCH PIPE WHICH WILL HEAT 1000
CUBIC FEET OF AIR PER MINUTE ANY REQUIRED NUMBER OF DEGREES,
THE TEMPERATURE OF THE PIPE BEING 200 FAHRENHEIT.

Temperature of
External Air.

Temperature at which the Room is required to be kept.

Deg. Fahr.

126

150

i74

200

229

259

292

328

367

409

119

142

166

I 9 2

220

251

283

318

357

399

112

135

159

184

212

242

274

309

347

388

105

127

J5 1

176

2O4

233

265

3 00

337

378

9 8

120

143

168

195

225

256

290

328

368

112

i35

1 60

I8 7

216

247

28l

3i8

358

105

128

152

179

207

238

271

308

347

7 6

120

144

170

199

229

262

298

337

6 9

112

136

162

190

220

253

288

327

IO4

128

154

181

211

243

279

317

120

173

202

234

269

307

112

137

164

193

225

259

296

104

129

155

184

215

249

286

9 6

1 2O

147

175

206

239

276

112

138

166

196

230

266

104

129

157

I8 7

220

255

121

148

178

210

245

112

132

168

2OO

235

I0 3

130

159

190

225

121

150

181

214

112

140

171

204

103

131

161

194

Hood, in his painstaking way, went to enormous trouble
to compile a table that would dispense very greatly with

however, is no fault), as, supposing it to be double the height of a green-
house, it would have practically the cubic area and side glass surfaces of
two green-houses, yet it would only have one top.

Quantities for Horticultural Works. 243

the complexity of the calculations needed by the rule he
laid down, this table being based upon the rule itself, but,
as it will be seen, making the total to be arrived at much
more easily discovered. This table, however, has one serious
objection viz., that it is based upon the pipe being at a
temperature of 200. Although this is quite possible, it is
not usually experienced in effect, and 180 should be con-
sidered the maximum* with skilled attention ; therefore,
if it is desired to make use of this table, one-fifth should be
added to the quantities of pipe given to allow for the pipe
temperature being 20 lower than that which Hood has
calculated upon.

It was mentioned that the glass was the sole cause of loss
of heat in horticultural work after the interior air and fixtures
were once heated. This is so ; but in the usual way it takes
three or four hours to get the heat up to the required degree
when first lighting, as, firstly, there is the volume of air to be
warmed, then all the interior fittings are absorbing heat on a
considerable scale ; and what takes even longer to cope with
is the amount of moisture that would exist in such an
instance and neutralize the general effect of the heat in a
great measure. A perfectly dry place would be heated up
much quicker.

Hood approximated the time that a glass house, with
a sufficiency of pipe and a boiler of corresponding power,
takes to become heated up as follows :

With 4-inch pipe .......... about 4^ hours.

3 .......... 3i

These times cannot be relied upon with any accuracy,
although they are useful to base an idea upon ; but in heating

* The word " maximum " is correctly used, for unless the fire receives
proper and sufficient attention from a person accustomed to the work,
1 80 will be the exception and not the rule.

t The results with 2-inch pipe are so much quicker, as they contain
much less water for a given amount of radiating surface than the larger
sizes.

R 2

244 Warming Buildings by Hot Water.

up, the time must vary by the condition of the interior fittings,
whether very damp, &c. ; the cubic contents, which vary very
greatly ; and the natural temperature of the atmosphere,
which varies still more. When the fire is started, the warmth
from the pipes goes to heat the air, and the air to heat what
it first comes in contact with, and for a little time the glass
has no cooling influence ; but as soon as the whole internal
air has attained a higher temperature than that outside, then
the cooling process is commenced, and it increases as the
heat inside is increased, until (supposing the quantity of pipe
to be exactly correct, &c.) they balance one another.

In the following rule for calculating quantities of pipe per
1000 feet cubic contents of glass houses, it must be repeated
again that the figures are approximate only, conditions and
position varying. In this table the pipe is supposed to be
kept at 1 80, and the extreme coldness of the outer air to be
10.* In the inspection of a greenhouse the following things
require consideration before fixing the quantity of pipe.

1. Its position, whether exposed, or sheltered by sur-
rounding houses, trees, or walls. If unusually exposed,
additional pipe should be used. (Span houses suffer most in
this respect.f)

2. Position with a lean-to house, as to whether it faces south,
south-west (the two best), or a more trying quarter. If not
south or south-west, some additional pipe should be allowed.

3. If not a large works, it is important to know how the
fire will be attended to. If by a coachman or boy, then a

* This can only be for a limited number of nights in winter. Some
fruits require a varying heat as tomatoes, which, when being ripened off,
are commonly given a higher than normal temperature ; but unusual
heats are never needed in mid-winter, and at other times nature will assist,
so that a maximum temperature of say 70 in winter can readily be in-
creased to 80 in spring.

t Span houses are commonly lower (taking a mean height) than lean-
to houses, and consequently have more cooling surface for the cubical
capacity than they would have if they were as high as the other houses.
A cube-shaped house would give us the least glass surface in proportion
to its internal capacity ; any deviation from this increases the cooling
surface.

Quantities for Horticultural Works. 245

good allowance in extra pipe should be allowed (and a little
larger boiler would be advisable).

The following table shows the length of 4-inch pipe needed
to keep up a given temperature to every 1000 cubic feet capacity
in a glass house for horticultural purposes, the pipe being at
1 80, and the outer air at 10 or higher (no ventilation when
outer air below freezing point).

Temperature
required.

Quantity of pipe to
each 1000 cubic feet.

Some of the purposes for which the
houses may be required.

Deg. Fahr.
9

feet.
80

Pines and forcing purposes.

] Tropical flowers and some ferns.

I Pits for melons, &c.

Grapes, strawberries.

5o
45

40
37

> Fruit trees, conservatories.

Trees, cuttings, stock, &c.

The above quantities are for lean-to houses, with one side
of brickwork ; if span houses (position not much exposed)
add one-fifth to the lengths or pipe given.

If pipes carried in trenches or channels, covered with a
grating, they must be calculated as being one-fourth less
effective than those that are exposed.*

Notwithstanding every care being used in compiling the
above Table, which will in practice be found safe and give
the results quoted, it is yet better to allow more pipe still ;
economy is not of first importancef; even 15 per cent, more
pipe could advantageously be used, requiring less attention at

* If the channels are not of full size the pipe will be still less effective.

t No such allowance is necessary if the works are for a professional
grower or an amateur on a large scale, as there would be highly-skilled
attendants employed.

246 Warming Buildings by Hot Water.

the furnace and further obviating risk of failure, as it must be
remembered that for the heat to go down on one occasion
only is sufficient to cause disastrous results if the weather be
severe.

The remarks in the right hand column of this table are,
to a great extent, useless, as it must not be supposed the hot
water engineer is the person to fix the temperature for certain
purposes. It is understood he has to receive instructions in
this respect from the gardener.

Notwithstanding the use of this rule it can be recom-
mended as a wise precaution that the area of glass be also
measured as accurately as possible, and the amount of pipe
required calculated by Hood's table, and so let one method
check the other. This will, it is to be hoped, bring the
result as close to accuracy as it is possible, as should the
two calculations differ to a serious extent, it will at once
indicate the existence of some unusual circumstance in con-
struction. This may be considered a deal of trouble, but it is
trouble worth taking. Nearly every one has heard of failures
occurring in hot water works of this kind. They are not
infrequent, but in nearly all such failures the apparatus will
be found correctly erected but insufficiently effective, the
calculations having been wrong somewhere, either in boiler
or pipes, or both. It will not be forgotten to allow upon
Hood's table, as explained just before it.

CHAPTER XII.

FUEL, STOKING, AND ATTENTION TO HORTICULTURAL

WORKS.

Fuel Steam coal, coke, &c., and its use Sulphur Stoking and regula-
tion of the fire Damping down Attention to air vents Flue cleaning
Frost, and precautions necessary Non-freezing solution Clean sur-
faces to ensure full radiation of heat.

It is desirable, perhaps, before closing the description of
horticultural hot-water works, to mention a few things in
connection with the use of the apparatus, and as to stoking,
&c., also as to some different features in these undertakings
that require attention after the work is complete.

The fuel used in these boilers * is almost as varied as
fuels can be, as in many places, badly situated for con-
veniently obtaining what may be best suited, resource has to
be had to wood and even peat, when the coal or coke has run
short ; in fact, anything that evolves heat will do temporarily
if the apparatus is not on a large scale ; but with such fuel as
wood, a deal more attention would be needed. Wood in
blocks, made by cutting about a 6-inch tree branch into 6-inch
lengths will be found fairly successful when nothing better
can be obtained at the moment required.

The customary fuel for very large boilers, brick set, is
hard steam coal. This coal has -a moderate percentage of
bituminous properties, sufficient to cause a useful and effective
amount of flame, without making such a heavy deposit of
soot, as the softer kinds of coal do, which commence to flare
before they are at a really intense heat, the soot not only
preventing the water having the benefit of the heat evolved

* For both horticultural and building works.

248 Warming Buildings by Hot Water.

by its low conductivity,* but also represents so much lost fuel
fuel converted into a form in which it cannot be usefully
employed for giving heat. The steam coal, although having
a flame and causing a sort of deposit, does not have this latter
disadvantage in nearly such an aggravated form as the soft
coal ; as in the first place its bituminous properties are
limited ; and, secondly, in burning it reaches a much higher
temperature and state of incandescence than the other, which
greatly aids in reducing the formation of soot.

This coal is not expensive, from i6s. to 19^. per ton
delivered in London in one or two ton lots (small quantities),
and it is very economical in use, it being so lasting in com-
bustion ; but it is not so inexpensive as what is known as
slack, which is coal-pickers refuse, not necessarily small, but
very mixed usually, and costing practically nothing but cost
of transit from the pit Slack is not so good in general
results as hard steam, and not so clean, but some people
minimise its drawbacks to some extent, by mixing coke with
it. A mixture of coal and coke is a very effective fuel.

For medium-sized brick set and for independent boilers
of practically every kind, coke without any coal admixed is
best, and is used more largely than any other fuel. Coke,
when fairly alight, evolves a most intense heat, as it so
readily becomes incandescent, and there are then no obstacles
(smoke and soot being absent) whatever to the boiler experi-
encing its full effectiveness. No doubt the absence of soot is
a great factor in the good results obtained, as the surfaces,
particularly in the flues, are kept so clean, and it will be found
that the heated air and hot gases from a coke fire do excellent
work outside a boiler ; not so much as flame at first starting
perhaps, but flame, by the soot it carries, so soon neutralises
its capabilities to some extent.

Coke, however, has rather a deleterious effect upon iron
work by reason of the active action of the sulphur contained

* Were it possible, soot would be fairly effective to put outside inde-
pendent boilers to prevent loss of heat, as it ranks moderately high as a
low conductor.

Fuel and Stoking. 249

in it. This sulphur is, of course, present in coal, even to a
greater extent than with coke, as in the conversion of coal to
coke a deal of sulphur is carried off with the gas ; but it will
be found that in the consumption of coal the sulphur is not
nearly so noticeable, as different causes tend to render it more
inactive as against the iron work. The activity of the sulphur
with coke is, however, not very objectionable upon surfaces
which are kept at a low temperature by water being in contact
with them on the other side, and the present form of welded
wrought boiler, which has all smooth surfaces, suffers very little
indeed ; but this cannot be said with the furnace fittings or
with any projecting parts from a boiler itself, and with rivetted
boilers it is generally considered that the ultimate failure of
the rivet heads on the heating surfaces is due to the insidious
action of the sulphurous acid, when coke is used. With coal
fuel, the rivet heads do not suffer nearly so much, although the
coal may have exactly the same percentage in it as the coke.

Notwithstanding the sulphur, coke is the best fuel for
nearly all boilers, and it is of particular advantage with those
boilers which have a complexity of tubes or irregular heating
surfaces, and which would be of some trouble to keep clean
of soot. With the small forms of independent boiler, all the
cinders from the house fires can be successfully used.

A deal of skill can be shown in stoking a furnace, even
with those of a small size, and with those of large capacity it
is, of course, well known that stoking is a calling in itself,
needing some intelligence. With boilers for ordinary hot-
water works, however, it is only necessary to point out a few
rules for general observance.

The most effective fire, that is, the one to give the greatest
results with the least expenditure of fuel, is that which is
always kept bright, and this can only be done by frequent
and regular attention. It is necessary with this object in
view to keep a rather thin layer of fuel upon the furnace bars
(except when banking up for the night) ; as apart from the
brightness of the whole of the fuel, the combustion is rendered
more perfect with less formation of carbonic oxide (see

250 Warming Buildings by Hot Water.

Combustion). With coal fuel it is the custom to make
use of the dead plate immediately inside the furnace door
for receiving a charge of fuel, so that it may be dried and
partially coked, the more volatile products being thrown off
as it lies at this point, and these products having to pass
across the incandescent fuel, undergo combustion, and do
effective work instead of going to form soot, as they would
have done if the coal was put directly upon the fire. It is
very improper to force fires, that is, get them up to a fierce
state in a short time, it should be quite unnecessary, and is
commonly evidence of bad stoking. This frequently happens
with a new apparatus in a building, where the attendant is an
odd man, not having the skill a gardener would, and being
unacquainted with the work, the consequence being that the
water becomes overheated ; and unless the boiler has an
expansion pipe directly from it, and this of good size, there
will be an overflow at the supply cistern by the generation of
steam at the boiler. When this occurs it is most quickly
stopped by opening the front furnace door, which will permit
of a free passage of cold air over the fire to the flue, and the
boiler will be cooled, and the effect of the fire be lessened.

If the boiler is fully large for the work the risk of over-
heating is increased, but this risk can only be for the first few
days, as the attendant should quickly become acquainted
with the use of the dampers, and then the advantages of the
larger boiler become apparent, for with the greater effective-
ness of the large fire, the dampers can be nearly closed,
attention in feeding the fire reduced to a minimum, and in
the end it will be found that a saving of fuel is effected by
reason of the lessened draught and speed of combustion,
although the boiler takes a larger charge of fuel in the first
place. It is the common practice for gardeners to use the
front furnace door to lessen the heat, instead of altering the
damper in the chimney.

In charging the boiler with fuel for the night, it is usual
and best to place some ash on top to " damp " the fire dowc
as it is termed, the real effect of the ash being to choke all

Attention to Apparatus. 251

the little air passages between the fuel, and smother it to an
extent. A fire skilfully " damped " down will keep alight for
an incredible time, but it is only for the night that this
practice is adopted, as it causes the fire to get into a dirty
state, and would be less effective after some few hours, un-
less it was raked and cleaned as requires to be done each
morning. This latter attention does not necessitate with-
drawing the active fuel from the furnace. In an apparatus
having air-cocks, it is very necessary that these be opened to
discharge the air frequently. It will be found that air accu-
mulates at the high points in the apparatus (of any kind)
very rapidly, and it is a good plan to open the air-cocks as
often as twice a week, as in many instances the accumulation
of air may be at a point where a small quantity will interfere
with or wholly check the circulation.*

The time for cleaning the flues varies from several causes,
but experience quickly fixes the time in which it should be
done, as the attendant can so readily judge by the quantity
of soot or dirt that he removes. Attendants' ideas, however,
vary, as those who have the time and the desire clean the
flues very frequently daily, as it renders the boiler more
effective, and is consequently a good practice. With coke
fires, attention in cleaning is still needed, but not with such
frequency as when soot is formed. The deposit from coke is
a fine dust, that will be found in the greatest quantity on
horizontal surfaces, or anywhere that it can rest.

Frost has particularly to be guarded against in all hot
water works, but more particularly to those devoted to horti-

* A peculiar instance of this came to the writer's notice quite recently ;
a school dining hall insufficiently heated by the fires was fitted with some
radiators in connection with a hot water apparatus. They were a success
for a week or two and then failed, and the master instead of mentioning
the matter took it for granted that the work was a failure, and actually let
the matter rest for nearly two years, when it was discovered that the air
taps had never been opened, and the radiators had been full of air all
this time. No water could get into them to be of use, as they were of the
kind that have upright pipes, which necessitates their being quite full to
permit the water to circulate.

252 Warming Buildings by Hot Water.

culture. There ought not, however, to be any fear that frost
will be permitted to act upon the contents of a glass house
unless the attendant be exceedingly careless, but there are
other effects of frost that need be guarded against.

If a new apparatus be cpmpleted during severe weather
it should not be charged and left full of water unless it is
convenient to light the fire at once, and to keep it alight
night and day, and in the same way no existing apparatus
should have the fire drawn, and be allowed to cool down,
unless it is intended to at once withdraw all the water it
contains, as should the water in the pipes, radiators, or any
other parts be allowed to freeze considerable damage will be
caused.

It is unnecessary to deal with the question of the ex-
pansion that takes place when water freezes. This, in a
general way, is within everyone's knowledge, and it is suffi-
cient to point out that no cast or wrought iron pipes, used in
a hot water apparatus, are strong enough to withstand its
effect, and a fracture must occur, unless by some favourable
circumstances there was a space into which the water could
expand itself without resistance. Sometimes an expansion
joint of one of the many kinds will prevent damage, as the
force exerted will disjoint the pipe, but this cannot be relied
upon by any means, for the expansion is very sudden. The
smaller the pipe the quicker the water freezes, and the only
really good remedy is to keep the fire alight or to empty the
apparatus.

There are now to be obtained materials that will success-
fully prevent water freezing at the lowest English temperature.
Mr. Stainton* patented a solution containing as its chief in-
gredient chloride of calcium, and this permits of water retain-
ing its fluidity at an intense degree of cold. Common salt is

* Of the firm of W. Stainton and Sons, a firm of high repute in general
hydraulic engineering. His invention was for the object of preventing the
water being frozen in the pipes of high-pressure apparatus, which cannot
be so readily emptied and refilled, certainly not by an inexperienced person,
and for this purpose the invention is a decidedly valuable one.

Attention to Apparatus. 253

effective in a moderate way, as water will take sufficient of
this material in solution (about 30 per cent.) to prevent its
freezing at our lowest known temperature, but for various
reasons it has never gained favour, and it is not the writer's
intention to recommend it. It requires to be mentioned that
if a boiler and apparatus be emptied, great care should be
exercised to see that they are filled before the fire is lighted,
as not only would injury be done to the boiler, but the inflow
of water on to hot boiler plates would probably cause an
explosion of a very serious character.

It is also necessary to protect air pipes from frost. They
should always be arranged so that the part of the pipe that
contains water is within the house, only the empty portion
passing outside. It is not always necessary to carry the air
pipe outside at all, but it is usually done in case of the boiler
overheating, and steam or water being ejected.

All radiating surfaces, pipes, &c., should be kept quite
clean, otherwise the heat will not pass from them freely,
depending upon the thickness of dust. Pipes in trenches
and beneath gratings are apt to be neglected, and the same
remark applies to coils of pipes in cases.

Every portion of pipe that is not used for radiating should
be covered with a material to prevent loss of heat (see
p. 120), as otherwise the heat it diffuses will be totally lost,
and represent so much wasted fuel, even supposing the boiler
is powerful enough to allow of the waste.

254 Warming Buildings by Hot Water.

CHAPTER XIII.

UPON WARMING BUILDINGS (LOW PRESSURE).

THE preceding papers have dealt almost exclusively with
horticultural works, but it will be found that there are many
minor points that apply to all hot water works alike, and
instead of repeating any of the information given it is pro-
posed, as the subjects are reached that have already been
mentioned, to make reference to the pages where these
questions are dealt with.

In treating the heating of buildings, the various pheno-
mena relating to circulation, radiation, &c., are actuated by
precisely the same natural laws as in horticultural works, but
the circumstances and conditions are so totally different as to
make it almost a distinct calling, so much so that a man
accustomed to glass house work wholly, would be at a loss to
erect hot water plant for buildings unless he had considerable
tuition, in the same way that he would be incapable of erecting
a circulating apparatus for domestic hot water supply (see

P- 329>

In hot water works for buildings, where the apparatus
extends upwards, perhaps, several floors, there is introduced
a feature which is not present in horticultural works that
rarely extend more than a few feet above the boiler, this
feature being the great strain that is exerted upon the lower
parts of the apparatus by the pressure or weight of water.

For the information of those unacquainted with hydraulics

Distinctive Features in Building Works. 255

it must be explained that this has no reference whatever to
the bulk of water, as this makes no difference, whether the
quantity be large or small. The pressure of water in pipes is
exactly proportionate to its weight viz., that the contents of
a pipe two feet four inches high,* and having an internal area
of one square inch (the nearest sized pipe we have to this is
ij inch diameter) will, when full, contain I Ib. of water, ana
a boiler having a pipe this length connected with it vertically,
and fitted with water, would be said to have a pressure of
I Ib. to the square inch within it, this pressure being as stated
merely the weight of I Ib. of water pressing within it.

The common impression would be that this pressure of
I Ib. would be distributed over the whole of the boiler (which
is correct), but diminished by being spread over a large
surface. This, however, is not the case, as the pressure of

1 Ib. will be exerted upon every square inch inside the boiler,
top, bottom, and sides, so that the aggregate pressure brought
to bear upon a moderate sized boiler by the contents of this
short length of pipe may be two tons,f and this needs con-
sideration in various ways in the works now alluded to, as we
do not have merely the effect of this short length of pipe to
deal with, but with an effect twenty times as great when the
apparatus extends up three or four floors.

Another, what may almost be termed a peculiarity, is that
the effect is precisely the same with any sized pipe that may
be used, whether it be J inch or 4 inch, but it is only vertical
pipe that counts that is, the vertical height between the
supply or feed cistern and the boiler will give the pressure
exerted in the boiler by calculating I Ib. for every 2 feet 4
inches of this measurement in question. From the boiler
upwards the pressure diminishes in exactly equal ratio, every

2 feet 4 inches in height the pressure per square inch in th c

* This may be termed practical measurement ; it is not strictly correct,
as the actual figures are 4328 of a pound to the foot.

t Any treatise upon hydraulics or hydrostatics explains this. Without
this peculiar phenomena the hydraulic lift, hydraulic press, &c., would be
of no use.

256 Warming Buildings by Hot Water.

pipe, or in any appliance connected with the pipe, being
reduced I Ib.

In case it may not be clear to all the readers why the
pressure is precisely the same with any sized pipe, it may be
explained that the standard of pressure is a supposed mass
of water 2 feet 4 inches high and I inch square, this mass or
body weighing exactly I Ib. Now, if we could stand this
upright, we should have one end of it standing upon a space
exactly I inch square, and this small space would be pressed
upon by a weight of I Ib. If we took another body of water
exactly the same size and placed it close up against the other
they would together be a quantity representing the contents
of a pipe with an internal area of 2 square inches, and we get
double the weight or pressure, but the pressure is upon 2
square inches of space at the bottom ; we have not increased
the pressure per square inch. We have doubled the pressure
certainly, but taken double the space to exert it upon, or, in
other words, a pipe of a size equal to 2 square inches exerts
double the pressure of a pipe of I square inch, but as it exerts
it upon double the area there is no increase of pressure per
square inch. On the other hand, a pipe of an area of half a
square inch would only contain sufficient water to exert a
pressure of half a pound for every 2 feet 4 inches of its
height, but this half pound would be exerted upon every
half square inch in the boiler, and so with the reduced pipe
there would be no reduction of pressure per square inch in
the boiler.

The same reasoning permits us to have a various number
of pipes entering the boiler without in any way varying the
pressure, as the pressure of water, both in the pipes and boiler,
exerts itself exactly in all directions. No one pipe would
cause more pressure than another, and no part of the boiler
would escape more than another. It will also be understood
that it matters not what quantity of water is contained within
the feed-system, the fact of the cistern having a large capacity
makes no difference if the height of the cistern remains the
same. Of course, if we had a tall cistern full to the top, there

Distinctive Features in Building Works. 257

would be a greater pressure exerted than with a shallow
cistern, supposing both were upon the same floor. The height
of the water-line in the cistern adds to the pressure in the
boiler exactly as if it were a pipe, viz., one pound to the
square inch for every 2 feet 4 inch vertically.

This strain upon a boiler has no injurious effect to speak
of, but it firstly necessitates the use of a proper-shaped boiler
when a high pressure has to be borne (say, for three or more
floors of a warehouse), as the ordinary saddle boiler, even
of |-inch plate, may become bulged on the inner side, even
when first charged and cold ; and it does not permit of the
boiler being used so long as with a low pressure, for so soon
as the boiler gets a little weak from wear and tear, the heavy
pressure will bring about its destruction. With low pressure
works the boiler might wear until it was quite thin, and still
do good service.

If the boiler were small there would be no particular fear
of bulging, but with a plain saddle boiler, four or five feet long,
it would be most probable, and consequently, when a strong
pressure has to be borne, a strong form of boiler is used, and
preference is commonly given to a cylindrical shape, as a
cylinder is capable of bearing enormous strains if equally
distributed inside, as it would be with water (or steam). To
those, however, who wish to avoid responsibility in this
respect, it may be suggested that the vertical pressure be
mentioned to the boilermaker, when purchasing, and he will
then supply what he can safely be responsible for.

In the bursting of a circulating apparatus containing water
only (an exceedingly rare occurrence) there is no danger
whatever to be feared, unless it occurred through the expan-
sion pipe, and all such outlets being tightly closed (by frost),
as in this case probably steam might be generated, which
would be an element of great danger. If a burst occurred
through the mere pressure or weight of water, there would
instantly be a violent outrush of the liquid, but this would
only be harmful to those who might be near enough to be
scalded, supposing the water was at a high temperature,

258 Warming Buildings by Hot Water.

further than this nothing need be feared. It is such a different
matter with steam, for the elasticity of this fluid has a rending
effect of a truly terrific nature when the steam is at high
pressure, and a burst is a highly dangerous occurrence.
Water may be considered (for the purposes of this paper)
incompressible, and consequently inelastic, as it can only be
compressed one-sixteenth of its volume under a pressure of
20,000 Ibs. to the square inch.

There is an erroneous idea, somewhat prevalent amongst
workmen, that the pressure, in an apparatus that extends
some distance vertically, aids the circulation. Perhaps this
error is fallen into easily from the fact that, as a rule, the
greater the pressure, the more rapid the circulation, for an
increase of pressure indicates increase in height, and, as a
general result, we may always look for a quicker circulation
the higher we go (see p. 63). But it must be clearly under-
stood this is in no way accounted for by the pressure, which
is exerted equally in all parts, and if it increased the flow of
water down the " return " pipe, it would just as greatly retard
the flow of water up the "flow" pipe, for it presses with
practically equal force down each. The erroneous idea, how-
ever, is fairly common, and workmen will be found sometimes
putting the supply cistern much higher than necessary with
the view to increase the circulation ; a very unnecessary thing
in these works, as a rule.

The circulation, that is, the strength of the motive power
and speed at which the water circulates, is, in these works, if
properly constructed, everything that could be desired, as
reference to p. 63 will make clear, and is sufficient to over-
come many obstacles that would render a horticultural appa-
ratus inefficient by reason of the exceedingly low motive
force in these latter works.

There is invariably a high speed of circulation in all verti-
cal apparatus, but the motive power does not increase in exact
ratio with the increased height of the pipes, and we might
reasonably expect that there could be a height which would
not permit of the circulation taking place at all, but this limit

Main Pipes in Building Works. 259

is never reached in building works of an ordinary character,
even with the highest blocks of warehouses that exist at
present,* neither is it likely to be reached just yet.

There is another result introduced in vertical works that
sometimes needs consideration, which is, that with a rapid
circulation in the main pipes, there is a likelihood of the
water passing by the branch services without freely circu-
lating through them as it should do ; but this does not need
such very particular attention in the ordinary way, and any
methods for overcoming this difficulty, can be better explained
when showing some example works (pp. 280 to 300).

The main pipes of these erections are, as a rule, rather
small compared to those in greenhouse work, for with the high
velocity of the circulation, frictional resistance plays a less
important part. No rule can well be laid down to determine
the size of the mains, as their capacity may be ruled by
various incidental features ; but commonly their increase or
decrease in size would be governed by the greater or less
quantity of water contained in the radiating media,f the
greater or less quantity of radiating surface (which would
vary the quantity of hot water to be brought to replace that
which has lost its heat), and lastly, the greater or less vertical
height, which governs the motive power. The higher the
motive power the less size the main pipes need be.

There is no gain whatever in having the main pipes larger
than is really necessary, as, assuming them to be exposed,
they would lose more heat if large than if small, and they
would increase the bulk of water to be heated, this increase

* If we ever have buildings of enormous height, there is no doubt that
any heating by hot water would be done by two or more boilers placed
at different heights, each boiler taking so many floors. If it were
attempted to heat all floors from one boiler in the basement, it would
need one of enormously strong make ; the joints of the radiating media
would also have to be very strong (at the lower floors), and there would
have to be a range of boilers and many separate main services, otherwise
we should be poorly supplied with heat at some points.

t Some of the modern radiators have a very large radiating surface for
the quantity of water they hold.

S 2

260 Warming Buildings by Hot Water.

being of no service in the usual way. Of course, if any part
of the main pipes are used for radiating purposes, this argu-
ment will not hold good ; but this again is not a usual
practice. Suggested sizes for main pipes will be spoken of
when treating of example apparatus.

The question of covering pipes that are used merely for
conveyance of water, and not for radiation, was spoken of in
horticultural works, p. 120, and will be found again referred
to under hot water for domestic purposes, p. 329 ; these latter
works are more ne