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MECHANICS OF THE HOUSEHOLD
* * * * * *
_McGraw-Hill Book Co., Inc._
PUBLISHERS OF BOOKS FOR
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* * * * * *
MECHANICS OF THE HOUSEHOLD
A Course of Study Devoted to Domestic Machinery and
Household Mechanical Appliances
E. S. KEENE
Dean of Mechanic Arts
North Dakota Agricultural College
FIRST EDITION
Mcgraw-Hill Book Company, Inc.
239 West 39th Street. New York
London: Hill Publishing Co., Ltd.
6 & 8 Bouverie St., E. C.
1918
Copyright, 1918, by the
Mcgraw-Hill Book Company, Inc.
INTRODUCTION
This book is intended to be a presentation of the physical principles
and mechanism employed in the equipment that has been developed for
domestic convenience. Its aim is to provide information relative to
the general practice of domestic engineering. The scope of the work is
such as to present: first, the use of household mechanical appliances;
second, the principles involved and the mechanism employed. It is not
exhaustive, neither does it touch many of the secondary topics that
might be discussed in connection with the various subjects. It does,
however, describe at least one representative piece of each type of
household apparatus that is used in good practice.
The mechanism used in the equipment of a modern dwelling is worthy of
greater attention, as a course of study, than it has been heretofore
accorded. The fact that any house, rural or urban, may be provided with
all domestic conveniences included in: furnace heating, mechanical
temperature regulation, lighting facilities, water supply, sewage
disposal and other appliances, indicates the general use of domestic
machinery in great variety. To comprehend the application and
adaptability of this mechanism requires a knowledge of its general plan
of construction and principles of operation.
Heating systems in great variety utilize steam, hot water, or hot air
as the vehicle of transfer of heat from the furnace, throughout the
house. Each of these is made in the form of special heating plants that
may be adapted, in some special advantage to the various conditions of
use. A knowledge of their working principles and general mechanical
arrangement furnishes a fund of information that is of every day
application.
The systems available for household water distribution take advantage
of natural laws, which aided by suitable mechanical devices and
conveniently arranged systems of pipes, provide water-supply plants to
satisfy any condition of service. They may be of simple form, to suit
a cottage, or elaborated to the requirements of large residences and
made entirely automatic in action. In each, the apparatus consists
of parts that perform definite functions. The parts may be obtained
from different makers and assembled as a working unit or the plant
may be purchased complete as some special system of water supply. An
acquaintance with domestic water supply apparatus may be of service in
every condition of life.
The type of illumination for a house or a group of buildings, may be
selected from a variety of lighting systems. In rural homes, choice may
be made between oil gas, gasolene, acetylene and electricity, each of
which is used in a number of successful plants that differ only in the
mechanism employed.
Any building arranged with toilet, kitchen and laundry conveniences
must be provided with some form of sewage disposal. Private disposal
plants are made to meet many conditions of service. The mechanical
construction and principles of operation are not difficult to
comprehend and their adaptation to a given service is only an
intelligent conception of the possible conditions of disposal,
dependent on the natural surroundings.
There are few communities where household equipment cannot be found to
illustrate each of the subjects discussed. Most modern school houses
are equipped for automatic control of temperature, ventilation and
humidity. They are further provided with systems of gas, water and
electric distribution and arrangements for sewage disposal. These
facilities furnish demonstration apparatus that are also examples of
their application. Additional examples of the various forms of plumbing
and pipe fittings, valves, traps and water fixtures may be found in the
shop of dealers in plumbers and steam-fitters supplies.
Attention is called to the value of observing houses in process of
construction and the means employed for the placement of the pipes for
the sewer, gas, water, electric conduits, etc. These are generally
located by direction of the specifications provided by the architect
but observation of their installation is necessary for a comprehension
of actual working conditions. It is suggested that the work be made
that of, first, acquiring an idea of established practice, and second,
that of investigating the examples of its application.
CONTENTS
PREFACE v
CHAPTER I
PAGE
THE STEAM HEATING PLANT 1
Heat of Vaporization--Steam Temperature--Gage Pressure--Absolute
Pressure--Two-pipe System--Separate-return System--Overhead
or Drop System--Water-filled Radiators--Air Vents--Automatic
Air Vents--Steam Radiator Valves--The House-heating Steam
Boiler--Boiler Trimmings--The Water Column--The Steam Gage--The
Safety Valve--The Draft Regulator--Rule for Proportioning
Radiators--Proportioning the Size of Mains--Forms of
Radiators--Radiator Finishings--Pipe Coverings--Vapor-system
Heating.
CHAPTER II
THE HOT-WATER HEATING PLANT 37
The Low-pressure Hot-water System--The High-pressure Hot-water
System--Heating-plant Design--Overhead System of Hot-water
Heating--Expansion Tanks--Radiator Connection--Hot-water
Radiators--Hot-water Radiator Valves--Air Vents--Automatic
Hot-water Air Vents.
CHAPTER III
THE HOT-AIR FURNACE 51
Construction--Furnace-gas Leaks--Location of the
Furnace--Flues--Combination Hot-air and Hot-water Heater.
CHAPTER IV
TEMPERATURE REGULATION 59
Hand Regulation--Damper Regulator for Steam Boiler--Damper
Regulators for Hot-water Furnaces--The Thermostat Motor--Combined
Thermostat and Damper Regulator--Thermostat-motor Connections.
CHAPTER V
MANAGEMENT OF HEATING PLANTS 70
General Advice--The Economy of Good Draft--General Firing
Rules--Weather and Time of Day--Night Firing--First-day
Firing--Other Day Firing--Economy and Fuels--For Burning Soft
Coal--For Burning Coke--Other Rules for Water Boilers--Air-vent
Valves on Radiators--The Air Valves--End of the Season--The Right
Chimney Flue--“Smokey” Chimneys.
CHAPTER VI
PLUMBING 82
Water Supply--Water Cocks--Bibb-cocks--Self-closing
Bibbs--Lever-handle Bibbs--Fuller Cocks--Wash-tray Bibbs--Basin
Cocks--Pantry Cocks--Sill Cocks--Valves--Kitchen and
Laundry Fixtures--The Bathroom--Bath Tubs--Wash Stands and
Lavatories--Traps--Back-venting--Soil Pipe--Water Closets--Washout
Closets--Washdown Closets--Siphon-jet Closet--Flush Tanks--Low-down
Flush Tank--Opening Stopped Pipes--Sewer Gas--Range Boilers--The
Water-back--Excessive Pressure--Blow-off Cock--Location of Range
Boiler--Double Heater Connections--Horizontal Range Boilers--Tank
Heaters--Overheater Water--Furnace Hot-water Heaters--Instantaneous
Heaters.
CHAPTER VII
WATER SUPPLY 125
Water Analysis--Pokegama Water--River Water--Artesian
Water--Medical Water--Organic Matter--Ammonia--Hardness
in Water--Iron in Water--Water Softening With Hydrated
Silicates--Chlorine--Polluted Water--Pollution of Wells--Safe
Distance in the Location of Wells--Surface Pollution of
Wells--Water Table--The Divining Rod--Selection of a Type of
Well--Flowing Wells--Construction of Wells--Dug Wells--Open
Wells--The Ideal Well--Coverings of Concrete--Artesian
Wells--Driven Wells--Bored Wells--Cleaning Wells--Gases in
Wells--Peculiarities of Wells--Breathing Well--Freezing
Wells--Pumps--The Lift Pump--The Force Pump--Tank Pump--Well
Pumps--Wooden Pump--Pumps for Driven Wells--Deep-well
Pumps--Tubular Well Cylinders--Chain Pumps--Rain Water
Cisterns--Filters--The Hydraulic Ram--Single-acting Hydraulic
Ram--The Double-acting Hydraulic Ram--Domestic Water-supply
Plants--Gravity Water Supply--Pressure-tank System of Water
Supply--The Pressure Tank--Power Water-supply Plants--Electric
Power Water Supply--The Water Lift.
CHAPTER VIII
SEWAGE DISPOSAL 168
The Septic Tank--The Septic Tank With a Sand-bed Filter--The Septic
Tank and Anaerobic Filter--Limit of Efficiency.
CHAPTER IX
COAL 182
Oxidation of Hydrocarbons--Graphitic Anthracite--Cannel
Coal--Lignite--Peat--Wood--Charcoal--Coke--Gas-coke--Briquettes
--Comparative Value of Coal to Other Fuels--Price of Coal.
CHAPTER X
ATMOSPHERIC HUMIDITY 196
Humidity of the Air--Relative Humidity--The Hygrometer--The
Hygrodeik--Dial Hygrometers--The Swiss Cottage
“Barometer”--Dew-point--To Determine the Dew-point--Frost
Prediction--Prevention of Frost--Humidifying Apparatus.
CHAPTER XI
VENTILATION 219
Quantity of Air Discharged by a Flue--Cost of Ventilation--The
Wolpert Air Tester--Pneumatic Temperature Regulation--Mechanical
Ventilation--The Plenum Method--Ventilation Apparatus--Air
Conditioning--Humidifying Plants--Vaporization as a Cooling
Agent--Air-cooling Plants--Humidity Control.
CHAPTER XII
GASEOUS AND LIQUID FUELS 250
Gaseous and Liquid Fuels--Coal Gas--All-oil Water Gas--Pintsch
Gas--Blau Gas--Water Gas--Measurement of Gas--Gas Meters How
to Read the Index--Prepayment Meters--Gas-service Rules--Gas
Ranges--Lighting and Heating with Gasoline--Gasoline--Kerosene--The
Cold-process Gas Machine--The Hollow-wire System of Gasoline
Lighting and Heating--Mantle Gas Lamps--Open-flame Gas Burners--The
Inverted-mantle Gasoline Lamp--Portable Gasoline Lamp--Central
Generator Plants--Central-generator Gas Lamps--Boulevard
Lamps--Gasoline Sad Irons--Alcohol Sad Irons--Alcohol Table
Stoves--Danger from Gaseous and Liquid Fuels--Acetylene-gas
Machine--Types of Acetylene Generators--Gas Lighters--Acetylene
Stoves.
CHAPTER XIII
ELECTRICITY 305
Incandescent Electric Lamps--The Mazda Lamp--Candlepower--Lamp
Labels--Illumination--The Foot-candle--The
Lumen--Reflectors--Choice of Reflector--Lamp Transformers--Units
of Electrical Measurements--Miniature Lamps--Effects of Voltage
Variations--Turn-down Electric Lamps--The Dim-a-lite--Gas-filled
Lamps--Daylight Lamps--Miniature Tungsten Lamps--Flash Lights--The
Electric Flat-iron--The Electric Toaster--Motors, Fuse
Plugs--Electric Heaters--Intercommunicating Telephones--Electric
Signals--Buzzers--Burglar Alarms--Annunciators--Table
Pushes--Bell-ringing Transformers--The Recording Wattmeter--To
Read the Meter--State Regulation of Meter Service--Electric
Batteries--Battery Formation--Battery Testers--Electric
Conductors--Lamp Cord--Portable Cord--Annunciator Wire--Private
Electric Generating Plants--Storage Batteries--The Pilot
Cell--National Electrical Code--Electric Light Wiring--Outlet
Boxes--Automatic Door Switch--Plug Receptacles--Heater Switch,
Pilot and Receptacle--Service Switch--Local Switches--Pilot
Lights--Wall and Ceiling Sockets--Drop Lights.
INDEX 385
MECHANICS OF THE HOUSEHOLD
CHAPTER I
THE STEAM HEATING PLANT
The use of steam as a means of heating dwellings is common in every
part of the civilized world. Plants of all sizes are constructed, that
not only give satisfactory service but are efficient in the use of
fuel, and require the minimum amount of attention.
The manufacture of steam heating apparatus has come to be a distinct
industry, and represents a special branch of engineering. Many
manufacturing companies, pursue this line of business exclusively.
The result has been the development of many distinctive features and
systems of steam heating, that are very excellent for the purposes
intended.
Practice has shown that large plants can be operated more economically
than small ones. Steam may be carried through underground, insulated
pipes to great distances with but small loss of heat. This has lead to
the sale of exhaust steam, from the engines of manufacturing plants,
for heating purposes and the establishment of community heating plants,
where the dwellings of a neighborhood are heated from a central heating
plant; each subscriber paying for his heat according to the number of
square feet of radiating surface his house contains.
In the practice most commonly followed, with small steam heating
plants, the steam is generated in a boiler located at any convenient
place, but commonly in the basement. The steam is distributed through
insulated pipes to the rooms, where it gives up its heat to cast-iron
radiators, and from them it is imparted to the air; partly by radiation
but most of the heat is transmitted to the air in direct contact with
the radiator surface.
The heating capacity of a radiator is determined by its outside surface
area, and is commonly termed, _radiating surface_ or _heating surface_.
Radiators of different styles and sizes are listed by manufacturers,
according to the amount of heating surface each possesses. Radiators
are sold at a definite amount per square foot, and may be made to
contain any amount of heating surface, for different heights from 12 to
45 inches.
The widespread use of steam as a means of heating buildings is due to
its remarkable heat content. When water is converted into vapor the
change is attended by the absorption of a large amount of heat. No
matter at what temperature water is evaporated, a definite quantity of
heat is required to merely change the water into vapor without changing
its temperature. The heat used to vaporize water in a steam boiler is
given up in the radiators when the steam is condensed. It is because of
this property that steam is such a convenient vehicle for transferring
heat from the furnace--where it is generated--to the place to be
warmed. This heat of vaporization is really the property which gives to
steam its usefulness as a means of heating.
=Heat of Vaporization.=--The temperature of the steam is comparatively
an unimportant factor in the amount of heat given up by the radiator.
It is the heat liberated at the time the steam changes from vapor to
water that produces the greatest effect in changing the temperature of
the house. This evolution of heat by condensation is sometimes called
the latent heat of vaporization. It is the heat that was used up in
changing the water to vapor. The following table of the properties of
steam shows the temperatures and exact amounts of latent heat that
correspond to various pressures.
When water at the boiling point is turned into steam at the same
temperature, there are required 965.7 B.t.u. for each pound of water
changed into steam. In the table, this is the latent heat of the
vapor of water at 0, gage pressure. As the pressure and corresponding
temperature rise, the latent heat becomes less. At 10 pounds gage
pressure, the temperature of the steam is practically 240°F., but the
heat of vaporization is 946 thermal units. When the steam is changed
back into water, as it is when condensed in the radiators, this latent
heat becomes sensible and is that which heats the rooms. The steam
enters the radiators and, coming into contact with the relatively
colder walls, is condensed. As condensation takes place, the latent
heat of the steam becomes sensible heat and is absorbed by the
radiators and then transferred to the air of the rooms.
PROPERTIES OF STEAM
---------+----------+-------------+---------
Absolute | Gage | Temperature | Latent
pressure | pressure | | heat
---------+----------+-------------+---------
0 | 14.7 | 212.00 | 965.70
1 | 15.0 | 213.04 | 964.96
2 | 16.0 | 216.33 | 962.63
3 | 17.0 | 219.45 | 960.49
4 | 18.0 | 220.40 | 958.32
5 | 19.0 | 225.25 | 958.30
6 | 20.0 | 227.95 | 954.38
7 | 21.0 | 230.60 | 952.50
8 | 22.0 | 233.10 | 950.62
9 | 23.0 | 235.49 | 949.03
10 | 24.0 | 237.81 | 947.37
11 | 25.0 | 240.07 | 945.76
12 | 26.0 | 242.24 | 944.25
13 | 27.0 | 244.32 | 942.74
14 | 28.0 | 246.35 | 941.29
15 | 29.0 | 248.33 | 939.88
16 | 30.0 | 250.26 | 938.50
17 | 31.0 | 252.13 | 937.17
18 | 32.0 | 253.98 | 935.45
19 | 33.0 | 255.77 | 934.57
20 | 34.0 | 257.52 | 933.32
21 | 35.0 | 259.22 | 932.10
22 | 36.0 | 260.88 | 930.92
23 | 37.0 | 262.50 | 929.76
24 | 38.0 | 264.09 | 928.62
25 | 39.0 | 265.65 | 927.51
---------+----------+-------------+---------
Whenever water is evaporated, heat is used up at a rate that in amount
depends on its temperature and the quantity of water vaporized.
This heat of vaporization is important, not only in problems which
relate to steam heating but in all others where vapor of water exerts
an influence--ventilation of buildings, atmospheric humidity, the
formation of frost, refrigeration, and many other applications in
practice; this factor is one of the important items in quantitative
determinations of heat. It will appear repeatedly in considering
ventilation and humidity.
At temperatures below the boiling point of water, the heat of
vaporization gradually increases until, at the freezing point,
it is 1092 B.t.u. Water vaporizes at all temperatures--even ice
evaporates--and the cooling effect produced by evaporation from
sprinkled streets in summer, or the chilling sensation brought about
by the winds of winter are caused largely because of its effect.
The evaporation of perspiration from the body is one of the means
of keeping it cool. At the temperature of the body 98.6 the heat of
vaporization is 1046 B.t.u.
=Steam Temperatures.=--While the temperature of steam is an unimportant
factor in the heating of buildings there are many uses in which it
is of the greatest consequence. When steam is employed for cooking
or baking it is not the quantity of heat but its intensity that is
necessary for the accomplishment of its purpose.
Steam cookers must work at a temperature suitable to the articles
under preparation, and the length of time required in the process.
Examination of the table on page 3, will show that steam at the
pressure of the air or 0, gage pressure, has a temperature of 212°F.,
which for boiling is sufficiently intense for ordinary cooking; but
for all conditions required of steam cooking, a pressure of 25 pounds
gage pressure is required. The temperature corresponding to 25 pounds
is shown in the table as 267°F. Baking temperatures for oven baking as
for bread requires temperatures of 400°F. or higher. To bake by steam
at that temperature would require a gage pressure of 185 pounds to the
square inch.
=The British thermal unit= is the English unit of measure of heat. It
is the amount of heat required to raise the temperature of a pound of
water 1°F. From the table it will be seen that steam at 10 pounds gage
pressure, is only 27.4° hotter than it was at 0 pounds. In raising the
pressure of a pound of steam from 0 to 10 pounds, the steam gained
only 27.4 B.t.u. of heat. The amount of heat gained by raising the
pressure to 10 pounds is small as compared with the heat it received on
vaporizing. The extra fuel used up in raising the pressure is not well
expended. It is customary, therefore, in heating plants, to use only
enough pressure in the boiler to carry the steam through the system.
This amount is rarely more than 10 pounds and oftener but 3 or 4 pounds
pressure.
=Gage Pressure--Absolute Pressure.=--In the practice of engineering
among English speaking people, pressures are stated in pounds per
square inch, above the atmosphere. This is termed gage pressure. It
is that indicated by the gages of boilers, tanks, etc., subjected
to internal pressure. Under ordinary conditions the term pressure
is understood to mean gage pressure, the 0 point being that of the
pressure of the atmosphere. This system requires pressures below that
of the atmosphere to be expressed as a partial vacuum, a complete
vacuum being 14.7 pounds below the normal atmospheric pressure.
In order to measure positively all pressures above a vacuum, the normal
atmosphere is 14.7 pounds; all pressures above that point are continued
on the same scale, thus:
Gage pressure 0 = 14.7 absolute
Gage pressure 10 = 10 + 14.7 = 24.7 absolute
Gage pressure 20 = 20 + 14.7 = 34.7 absolute
Absolute pressures are, therefore, those of the gage plus the
additional amount due to the atmosphere. All references to pressure in
this work are intended to indicate gage pressure unless specifically
mentioned as absolute pressure.
Steam heating as applied to buildings may be considered under two
general methods: the pressure system in which steam under pressure
above the atmosphere is utilized to procure circulation; and the
vacuum system in which the steam is used at a pressure below that of
the atmosphere. Each of these systems is used under a great variety of
conditions, and to some is applied specific names but the principle of
operation is very much the same in all of a single class.
Steam heating plants are now seldom installed in the average home
but they are very much employed in apartment houses and the larger
residences. In large buildings and in groups of buildings heated
from a central point, steam is used for heating almost exclusively.
The type of plant employed for any given condition will depend on
the architecture of the buildings and their surroundings. In very
large buildings and in groups of buildings, the vacuum system is very
generally employed. This system has, as a special field of heating, the
elaborate plants required in large units.
The low-pressure gravity system of heating is used in buildings of
moderate size, large residences, schools, churches, apartment houses,
and the like. Under this form of steam heating is to be included vapor
heating systems. This is the same as the low-pressure plant except
that it operates under pressure only slightly above the atmosphere and
possesses features that frequently recommend its use over any other
form of steam heating. The term vapor heating is used to distinguish it
from the low-pressure system.
=The low-pressure gravity system=, with which we are most concerned,
takes its name from the conditions under which it works. The low
pressure refers to the pressure of the steam in the boiler, which is
generally 3 or 4 pounds; and since the water of condensation flows back
to the boiler by reason of gravity, it is a gravity system.
The placing of the pipes which are to carry the steam to the radiators
and return the water of condensation to the boiler may consist of
one or both of two standard arrangements. They are known as the
_single-pipe system_ and the _two-pipe system_.
[Illustration: FIG. 1.--Diagram of a gravity system steam heating
plant.]
Fig. 1 shows a diagram of a single-pipe system in its simplest form.
In the figure the pipe marked _supply and return_, connects the boiler
with the radiators. From the vertical pipe called a _riser_, the steam
is taken to the radiators through branch pipes that all slope toward
the riser, so that the water of condensation may readily flow back into
the boiler. The water of condensation, returning to the boiler, must
under this condition, flow in a direction contrary to the course of the
steam supplying the radiators. In Fig. 2 is given a simple application
of this system. A single pipe from the top of the boiler, in the
basement, marked _supply and return pipe_, connects with one radiator
on the floor above. The radiator and all of the connecting pipes are
set to drain the water of condensation into the boiler.
[Illustration: FIG. 2.--A simple form of steam heating plant. The
furnace fire is controlled by a thermostat and a damper regulator.]
When the valve is opened to admit steam to the radiator, the air vent
must also be opened to allow the escape of the contained air. The steam
will not diffuse with the air in the radiator and unless the air is
allowed to escape, the steam will not enter. As the steam enters the
cold radiator, it is rapidly condensed, and collects on the walls in
the form of dew, at the same time giving up its latent heat. The heat
is liberated as condensation takes place, and as the dew forms on the
radiator walls the heat is conducted directly to the iron. The water
runs to the bottom of the radiator and then through the pipes; back
to the boiler. The water occupies but relatively a little space and
may return through the same pipe, while more steam is entering the
radiator. As the steam condenses in the radiator, its reduction in
volume tends to reduce the pressure and thus aids additional steam from
the boiler to enter. In this manner a constant supply of heat enters
the radiator in the form of steam which when condensed goes back to the
boiler at a temperature very near the boiling point to be revaporized.
It should be kept in mind that it is the heat of vaporization, not the
temperature of the steam that is utilized in the radiator, and that the
heat of vaporization is the vehicle of transfer. The water returning to
the boiler may be at the boiling point and the steam supplying the heat
to the radiators may be at the same temperature.
[Illustration: FIG. 3.--A gravity system steam heating plant of two
radiators. The furnace is governed by a thermostat.]
Fig. 3 is a slightly different arrangement of the same boiler as that
shown in Fig. 2, connected with two radiators on different floors. The
same riser supplies both radiators with steam and takes the water of
condensation back to the boiler.
Fig. 4 is an example of the single-pipe system applied to a small
house. In the drawing, the boiler in the basement is shown connected
with four radiators on the first floor and three on the second
floor. The pipes connecting with the more distant radiators are only
extensions of the pipes connecting the radiators near the boiler. As
in Figs. 1, 2 and 3, all of the pipes and radiators are set to drain
back into the boiler. If at any place the pipe is so graded that a part
of the water is retained, poor circulation will result, because of the
restricted area of the pipe, and the radiators will not be properly
heated. This lack of drainage is also a common cause of hammering and
pounding in steam systems, known as _water-hammer_. The formation of
water-hammer is caused by steam flowing through a water-restricted
area, into a cold part of the system, where condensation takes place
very rapidly. The condensation of the steam is so rapid and complete
that the resulting vacuum draws the trapped water into the space with
the force of a hammer stroke. The hammering will continue so long as
the conditions exist. The pipes in the basement are suspended from the
floor joists by hangers as shown in the drawing. In practice the pipes
in the basement are covered with some form of insulating material to
prevent loss of heat.
[Illustration: FIG. 4.--The gravity system steam heating plant
installed in a dwelling.]
As stated above, the single-pipe system may be successfully used in all
house-heating plants except those of large size. It requires the least
amount of pipe and labor for installation of the circulating system and
when well constructed performs very satisfactorily all of the functions
required in a small heating plant.
One of the commonest causes of trouble in a single-pipe system is due
to the radiator connections. The single radiator connection requires
the entering steam and escaping water of condensation to pass through
the same opening. Under ordinary conditions this double office of the
radiator valve is accomplished with satisfaction but occasionally it
is the cause of considerable noise. At any time the valve is left only
partly open the steam will enter and condense because of the lower
pressure inside the radiator but the condensed water will not be able
to escape. The water has only the force of gravity to carry it out of
the radiators and if it meets no opposition will flow back through
the pipe to the boiler; but if it is required to pass a small opening
through which steam is flowing in a contrary direction, the water will
be retained in the radiators. Single-pipe radiators, therefore, work
satisfactorily only under conditions which will permit the steam to
enter and the water to leave as fast as it is formed. In ordinary use
the valve at any time is apt to be left slightly open and this produces
undesirable working conditions.
In larger buildings, where greater distances require longer runs
of pipe and more complicated connections, and where the volume of
condensed steam is too great to be taken care of in a single pipe, this
system does not work satisfactorily.
=Two-pipe System.=--Fig. 5 is a diagram of a two-pipe system. Here,
each radiator has a _supply pipe_, through which the steam enters, and
a _return pipe_ which conducts the water away. The branch pipes from
a common supply pipe or riser, carry steam to the various radiators
and all of the return pipes empty into a single return pipe that takes
the water back to its source. It will be noticed that in this case
the _riser_ also connects at the bottom with the return pipe. This
connection is made for the purpose of conducting away the condensation
that takes place in the connecting pipes. The water will always
stand in these pipes, at the same height as the water in the boiler.
The supply pipe from the boiler, and the branch pipes connecting
the radiators all slope toward the _riser_. The condensation in the
connecting pipes does not pass through the radiators as it returns to
the boiler.
An exception to this general rule is shown in the radiator on the
second floor. In this case the supply pipe slopes downward as it
approaches the radiator. To prevent carrying water through the
radiator, a small pipe under the left-hand valve connects with the
return pipe and the water is thus conducted to the main return pipe.
[Illustration: FIG. 5.--Diagram showing the arrangement of a two-pipe
steam plant.]
Fig. 6 is a simple application of the arrangement shown in Fig. 5.
The steam may be easily traced from the boiler to the radiators, and
back through the return pipes to its source. The pipe marked _R_ is
the connection between the main supply pipe and the return pipe that
takes away the condensation of the riser. It is connected to the main
return pipe below the water line of the boiler and, therefore, does
not interfere in any way with the passage of the steam. Each radiator
empties its water of condensation into a common return pipe, that
finally connects with the boiler below the water line.
[Illustration: FIG. 6.--A two-pipe steam heating plant.]
This arrangement may be elaborated to almost any extent and is an
improvement over the single-pipe system. It is quite commonly used as
a method of steam distribution, but it lacks the required elements
necessary to a positive circulation. As an example: Suppose that the
plant shown in Fig. 6 is working and that the radiator on the first
floor is hot, but the valves of the radiator on the second floor are
closed and it is cold. The steam entering at the valve _A_ of the lower
radiator is being condensed as fast as the heat is radiated. The steam
will pass on through the valve _B_ into the return pipe and as soon as
the return pipe becomes hot it will contain steam at practically the
same pressure as that in the supply pipe. This is what takes place in
every working steam plant. Now suppose that it is desired to heat the
radiator on the floor above. The steam valve _A_ of the upper radiator
is opened to admit steam and the return valve is also opened to allow
the water to escape. There is steam in both the supply and return pipes
of the radiator below at the same pressure, each tending to send steam
into the radiator above at opposite ends. This would make a condition
exactly the same as a single-pipe system, with a supply pipe at both
ends of the radiator and the result would, of course, be the same as in
the single-pipe system. There being no place for the water to escape
except against the incoming steam, the water will sometimes surge back
and forth with the customary noises peculiar to such conditions. It
must not be understood that this will always occur, because systems of
this kind are in use with fairly good results, but noisy radiators are
not at all rare when working under this condition and the cause is from
that described. To overcome this difficulty and change the system into
one in which there would be a positive circulation from _A_ to _B_, in
each radiator, allowing the steam always to enter at the valve _A_ and
escape at _B_, the system must be changed to that of _separate returns_.
[Illustration: FIG. 7.--Diagram of a separate return steam system.]
=Separate-return System.=--A diagram of a _separate-return_ system is
shown in Fig. 7. In this figure, the radiator, boiler and supply pipes
are the same as those of Fig. 5, but there is a separate return pipe
from each of the radiators, connecting with the main return pipe at a
point below the water line of the boiler. Examination of this diagram
will show that there is an independent circuit for the steam through
each radiator. The steam is taken from a common riser as before but
after passing through the radiator the water is returned by a separate
pipe to the main return pipe at the bottom of the boiler. Fig. 8 is an
application of _separate-return_ system. It is exactly the same as Fig.
6, except that each radiator has an independent return pipe. Steam must
always enter the radiators at the valves _A_ and leave at the valves
_B_. This makes a positive circulation that renders each radiator
independent of the others. There is no opportunity for steam to pass
through one radiator and interfere with the return water of another;
it, therefore, prevents the possibility of hammering or surging so
common in poorly designed steam systems.
Of all the methods of steam heating where the water of condensation
is returned to the boiler by reason of gravity this is the most
satisfactory. This plant requires a larger amount of pipe than the
other systems described and as a consequence the cost of installation
is greater but it repays in excellence of service the extra expense
incurred.
[Illustration: FIG. 8.--A separate return heating plant.]
=Overhead or Drop System.=--There is yet another gravity system of
steam heating that is sometimes used in large buildings where economy
in the use of pipe is desired; this is the _overhead_ or _drop_ system
shown in Fig. 9. It is not a common method of piping and is given here
only because of its occasional use. In the arrangement of the _drop_
system, the supply pipe for the radiators rises from the boiler to the
highest point of the system and the branch pipes for the radiators are
taken off from the descending pipe. Its action is the same as that of
a single-pipe system but the advantage gained by the arrangement is
that the steam in the main supply pipes travels in the same direction
as the returning water of condensation; the cause of _surging_ in long
_risers_ is thus eliminated.
The two-pipe systems of steam heating are more certain in action than
the single-pipe methods because there is nothing to interfere with
the progress of the steam on its way to the radiators. In long branch
pipes of the _single-pipe_ system, the returning water is frequently
caught by the advancing steam and carried to the end of the pipe, when
_slugging_ and _surging_ is the result.
[Illustration: FIG. 9.--Diagram of the overhead or drop system steam
plant.]
=Water-filled Radiators.=--Radiators frequently fill with water and are
noisy because of the position of the valve. This may be true in any
gravity system but particularly so in radiators having a single pipe.
When the valve of a single-pipe radiator is opened a very small amount,
the entering steam is immediately condensed but the water cannot escape
because the incoming steam entirely fills the opening. Under this
condition, the radiator may entirely fill with water. If the valve is
then opened wide, the imprisoned water has an opportunity to escape
while the steam is entering, but the entering steam and escaping water
sets up a water-hammer that sometimes is terrific and lasts until the
water is discharged from the radiator. The same condition may exist
in a two-pipe system, if the steam valve is slightly opened while the
escape valve is closed, but in a well-designed system the radiator will
be immediately emptied when both valves are open.
=Air Vents.=--All radiators must be provided with air vents. The
vent is placed near the top of the last loop of the radiator, at the
end opposite from the entering steam, as indicated in Figs. 2, 3, 6,
etc. The object of the vent is to allow the air to escape from the
radiator as the steam enters. Steam will not diffuse with the air and,
therefore, cannot enter the radiator until the air is discharged.
The air vent may be a simple cock such as is shown in Fig. 10, that
must be opened by hand when the steam is turned on, to allow the air
to escape, and closed when the steam appears at the vent; or it may
be an automatic vent, that opens when the radiator cools and closes
automatically when the radiator is filled with steam. There are many
makes of air vents of both hand-regulating and automatic types; of
the former, Fig. 10 furnishes a common example. The part _A_, in the
figure, is threaded and screws tightly into a hole made to receive it
in the end loop of the radiator. The part _B_ is a screw-plug that
closes the passage _C_, leading to the inside of the radiator. When
the steam is turned on, the vent must be opened until the air is
discharged, after which it is closed by the hand-wheel _D_.
[Illustration: FIG. 10. FIG. 11. FIG. 12. FIG. 13.
FIG. 10.--A common form of air vent for radiators.
FIG. 11.--An inexpensive automatic radiator air vent.
FIG. 12.--Monash No. 16 automatic air vent.
FIG. 13.--The Allen float, radiator air vent.]
=Automatic Air Vents.=--These vents depend for their action on the
expansion of a part of the valve due to the temperature of the steam.
The valve remains closed when hot and opens when cold. The difference
in temperature between the steam and the expelled air from the radiator
is the controlling factor. In the automatic vent shown in Fig. 11, the
part _A_ is screwed into the radiator loop. The discharge _C_ is open
to the air or connected with a drip pipe, which returns the water to
the basement. The cylinder _D_, which closes the passage _B_, is made
of a material of a high coefficient of expansion. The piece _D_, when
cool, is contracted sufficiently to leave the passage _B_ open to the
air. When the steam is turned on, the expelled air from the radiator
escapes through _B_ and _C_, but when the steam reaches _D_ the heat
quickly expands the piece and closes the vent.
Most automatic vents require adjusting when put in place and
occasionally need readjustment. The cap _O_, of Fig. 11, may be removed
with a wrench and a screw-driver used to adjust the piece _D_, so as
to shut off the steam when the radiator is filled with steam. The
expanding piece is simply screwed down until the steam ceases to escape.
Fig. 12 is another style of automatic vent, constructed on the same
principle as that of Fig. 11, but probably more positive in action. In
this vent the part _A_ attaches to the radiator. The expanding portion
_B_ is made in the form of a hollow cylinder, through which the air and
steam escape to the atmosphere. It is longer than the corresponding
piece in the other vent and is more sensitive because of its greater
length and exposed surface. As the piece _B_ elongates from expansion,
the upper end makes a joint with the conical piece _D_. The shape of
this latter piece gives better opportunity for a tight joint than in
the other form of vent and in practice gives better service.
Fig. 13 is a cross-section of the Allen vent. This is an example of a
vent which depends for its action on a float. Whenever sufficient water
accumulates in the body of the vent to raise the float, it closes the
vent by means of its buoyancy. The body of the vent shown in Fig. 13 is
composed of two concentric cylinders. The float _E_ occupies the inner
cylinder, while surrounding it is the outer cylinder _D_. The outer
cylinder is entirely closed except a little hole at _G_. The float is
made of light metal and fits loosely in the inner cylinder. The steam
from the radiator condenses in the vent until the inner cylinder is
filled with water, up to the opening _A_. The float by its buoyancy
keeps the opening in _B_ stopped, and no steam can escape. The air of
the outer cylinder _D_ is expanded by the heat of the steam and most
of the air escapes through the hole _G_. When the radiator cools,
the rarefied air in _D_ contracts and draws the water from the inner
cylinder into the space _D_; this allows the float to fall and unstop
the opening in _B_. When the steam again reaches the vent, the heat
expands the air in _D_ and forces the water into the inner cylinder;
the float is again raised and stops the opening in _B_.
Many other air vents are in common use but most of them operate on
one or the other of the principles described. Fig. 11 is a relatively
inexpensive vent, while Fig. 12 is higher-priced.
[Illustration: FIG. 14.--Steam radiator valve.
FIG. 15.--Sectional view of a steam radiator valve.]
=Steam Radiator Valves.=--Like most other mechanical appliances that
are extensively used, radiator valves are made by a great number
of manufacturers and in many different forms. Some possess special
features that are intended to increase their working efficiency but the
type of radiator valve most commonly used for ordinary construction is
that illustrated in Figs. 14 and 15. It is a style of _angle valve_
that takes the place of an elbow and being made with _a union joint_,
also furnishes a means of disconnecting the radiator without disturbing
the pipes. Fig. 14 is an outside view of the valve and Fig. 15 shows
its mechanical construction. The part _B_ screws onto the end of the
steam pipe and _A_ connects with the radiator. The part _C-D_ is the
_union_. The nut _C_ screws onto the valve and makes a steam-tight
joint at _D_, between the parts. In case it is desired to remove the
radiator, it furnishes an easy means of detaching the valve. The
composition valve-disc _E_ makes a seat on the brass ring directly
under it, to shut off the steam. In case the valve leaks, the disc may
be removed by taking the valve casing apart at _G_. The worn disc can
then be replaced with a new one which may be obtained from the dealer
who furnished the valve. The only moving part of the valve exposed to
the air is at the point where the valve-stem _S_ enters the casing. The
joint is made steam-tight by the packing _P_. The packing is greased
candle wicking that is wound around the stem and held tightly in place
by the screw-cap _H_. If the valve leaks at this joint, a turn or two
with a wrench will stop the escape of the steam.
THE HOUSE-HEATING STEAM BOILER
House-heating boilers were formerly made of sheet metal and are still
so constructed to some extent, but by far the greater number are now
made of cast iron. Sheet-metal boilers are constructed at the factory,
ready to be installed, but the cast-iron type is made in sections
and assembled to make a complete boiler, at the time the plant is
erected. Sectional boilers are convenient to install, on account of the
possibility of handling the parts in a limited space, that would not
admit an assembled boiler without tearing down a part of the basement
for admission.
Cast-iron boilers as commonly used for heating dwellings are made in
two definite styles. The small sizes are cylindrical in form and are
used for either steam or hot-water heating. The larger sizes are made
as illustrated in Figs. 16 and 17, the former being an outside view,
and the latter showing the internal arrangement of the same boiler. The
fire-box, water space and smoke passages are easily recognized. Each
division represents a separate section which assembled as that in the
figures makes a complete boiler with a common opening as shown at the
top of Fig. 17. These boilers are used for residences of large size and
for buildings of less than 10,000 feet of radiating surface. For large
buildings, the steam is most commonly generated in boilers built for
high pressure.
In small plants, intended for either steam or hot-water heating,
the cylindrical style of boiler shown in Fig. 18 is commonly used.
As constructed by different manufacturers, the parts differ quite
materially but Fig. 18 shows all of the essential features and serves
to illustrate the different working parts. The sections into which the
boiler is divided are indicated on the left-hand side of the figure by
the numbers 1 to 6. The parts from 1 to 5 are screwed together with
threaded nipples, joining the central column. The part 6 contains the
grate and the ash-pit, with the draft and clean-out doors.
[Illustration: FIG. 16. FIG. 17.
FIG. 16.--Sectional cast-iron boiler for steam or hot-water heating.
FIG. 17.--Interior view of the boiler shown in Fig. 16.]
The drawing shows the boiler cut through the middle lengthwise and
exposes to view all of the essential features. The fire-box and the
spaces occupied by the steam and water are easily recognized. It will
be seen that the water space surrounds the fire-box except at the
bottom and that the space above the fire-box presents a large amount
of heating surface to the flame and heated gases as they pass to the
chimney. The arrows show their course; first through the openings near
the center, then through those further away. The object being to keep
the heat as long as possible in contact with the heating surfaces
without interfering with the draft.
[Illustration: FIG. 18.--Sectional view of the cylindrical type of
cast-iron, sectional boiler.]
There is no standard method of rating the heating capacity of boilers
of this kind and as a consequence, boilers of different makes--for the
same rating--are not the same in actual heating capacity. The boilers
are sold by their makers in sizes that are intended to furnish heat
sufficient to supply a definite number of square feet of radiating
surface. The ratings are quite generally too high for the weather
conditions of the Northwest. A common practice with contractors is to
select boilers for a given plant 50 per cent. and even 100 per cent.
larger than those rated by the manufacturers for the same amount of
radiation. Some manufacturers sell their boilers at honest ratings but
they are exceptions.
In specifying the capacity of a house-heating plant it is common
practice to require the boiler to be of such size as will easily heat
a definite number of square feet of radiating surface. The radiators
are required to possess sufficient radiating surface to keep the house
at 70°F. in any weather. In the absence of any rules or specifications
for determining the heating capacity of the boiler, the only means
of securing a satisfactory plant is to require a guarantee of the
contractor to install a boiler such as will fulfil the conditions
stated above.
=Boiler Trimmings.=--Attached to the boiler and required for its safe
operation are a number of appliances that demand special attention. The
office of each part should be thoroughly appreciated and the mechanical
construction should be fully understood. An intimate acquaintance with
the details of the plant, helps to make its operation satisfactory and
adds to the efficiency with which it can be made to perform its duty.
=The Water Column.=--In Fig. 18 the water column is shown at _C_.
It is attached to the boiler by pipes at points above and below the
water line, so as to allow a free passage of the water of the boiler
to the interior. The water line should be 3 or 4 inches above the top
heating surface. Attached to the water column is the _gage-glass_, the
_try-cocks_ _T_ and _T_ and the _steam gage_ _G_.
The object of the gage-glass is to show the height of the water in the
boiler. It is shown in place on the boiler in Figs. 16 and 18 and in
detail in Fig. 19. The lower part of the gage-glass occupies a position
on the boiler about 2 inches above the top heating surface. When the
boiler is working, the level of the water should always be visible in
the glass and should stand normally one-third to one-half full.
[Illustration: FIG. 19.--The water gage.]
The water gage is attached to the water column by two brass valves
_V_. The valves are provided so that in case the water glass should
be broken the openings may be closed. The ends of the glass are made
tight by “stuffing-boxes” marked _C_, in the figure. The packing _S_ is
generally in the form of rubber rings but greased wicking may be used
if necessary as in the case of valve-stems.
_The try-cocks_ _T_ and _T_ (Fig. 18) are also intended to indicate
the approximate height of the water in the boiler and should the
water glass be broken may be used in its place. The openings of the
try-cocks point toward the floor. When a cock is opened, should steam
alone escape, it will be absorbed by the air, but if water is escaping,
although much of it will be vaporized and look like steam, some of
the water will be carried to the floor and produce a wet spot. When
the cock is opened wide the escaping water from the lower cock should
always wet the floor.
_The drip-cock_ _P_ (Fig. 18) at the bottom of the gage-glass is for
draining the water column and for blowing out any deposit that may
collect in the opening of the column. This cock should be opened
occasionally to assure the correctness of the gage-glass.
[Illustration: FIG. 20.--Typical Bourdon pressure gage with the face
removed.]
=The Steam Gage.=--Steam pressure is measured in pounds to the
square inch above the pressure of the atmosphere. The gages used for
indicating the pressure of the steam are made in several forms but
the type most commonly used is that shown in Fig. 20. It is known as
the Bourdon type of gage and takes its name from the bent tube _A_,
which furnishes its active principle. The Bourdon barometer invented
in 1849 employed this form of sensitive tube. In the drawing the face
of the gage has been removed to show the working parts. The sensitive
part is the flat elastic tube _A_, which is bent in the form of a
circle. When the pressure of the steam enters at _S_ the air in the
tube is compressed and the tube tends to straighten. The movement of
the tube caused by the steam pressure is communicated to the pointer
by a link connection and gear as shown in the drawing. The amount of
straightening of the tube will be in proportion to the steam pressure
and is indicated by the numbers marked on the face of the gage. When
the pressure is released, the tube returns to its original position
and the spiral spring _C_ turns the hand back to its first position.
[Illustration: FIG. 21.--Cross-section of a pop valve.]
=The Safety Valve.=--All steam boilers should be provided with safety
valves as a safeguard against excessive steam pressures. Of the various
types of safety valves, that known as the _pop-valve_ is most commonly
used on house-heating boilers. It is indicated at _W_ in Fig. 18 and
is shown in section in Fig. 21. The part _A_ is screwed into the top
of the boiler at any convenient place. The pressure of the spring _C_
holds the valve _B_ on its seat until the internal pressure reaches a
certain intensity at which the valve is set, when it opens and allows
the excess steam to escape. When the pressure is reduced, the spring
forces the valve back on its seat. The handle _D_ permits the valve to
be lifted at any time as an assurance that it is in working order. This
should be done occasionally, as the valve may stick to the seat after
long standing and allow the pressure to rise above the point at which
it should “pop.”
The valve may be set to “blow off” at any desired pressure by the
adjusting piece _E_. House-heating boilers generally have their safety
valves set to blow off at 8 or 10 pounds.
=The Draft Regulator.=--As a means of automatic control of the steam
pressure, the draft regulator is frequently used to so govern the fire
that when a certain steam pressure is reached, the direct draft will
be automatically closed and the check-draft damper opened. The draft
regulator is shown in place at _D_ in Fig. 18, and will also be found
in Fig. 16. A detailed description of the regulator will be found on
pages 60 and 61.
RULE FOR PROPORTIONING RADIATORS
Rules for determining the amount of radiating surface that will
be required to satisfactorily heat a building to 70°F. regardless
of weather conditions are entirely empirical, that is, they are
derived from experience. It is evident that no definite rule can
be established that will take into account the method of building
construction, the kind and amount of materials that make up the walls
and the quality of workmanship employed. These variable quantities
coupled with the changing climatic conditions of temperature and wind
velocity produce a complication that cannot be overcome in a formula
that will give exact results.
Many rules are in use for this purpose, no two of which give exactly
the same results when applied to a problem. A common practice is to
apply one of the rules in use and then under conditions of exceptional
exposure, to add to the amount thus calculated as experience may
dictate.
The following rule by Professor R. G. Carpenter of Cornell University
was taken from a handbook published by the J. L. Mott Iron Works of New
York. This company manufactures and deals in all kinds of apparatus
entering into steam and hot-water heating and the rule is given as one
that has produced satisfactory results.
RULE.--Add the area of the glass surface in the room to one-quarter
of the exposed wall surface, and to this add from one-fifty-fifth
to three-fifty-fifths of the cubical contents (one-fifty-fifth for
rooms on upper floor, two-fifty-fifths for rooms on first floor and
three-fifty-fifths for large halls); then for steam multiply by 0.25,
and for hot water by 0.40.
_Example._--A room 20 by 12 by 10 feet with glass exposure of 48 feet,
1/4 of wall exposure (two sides exposed) 320 feet = 80, 1/55 of 2400 =
44.
48 + 80 + 44 = 172 × 0.25 = 43 feet.
If you add 2/55 the surface would be 54 feet.
If you add 3/55 the surface would be 65 feet.
PROPORTIONING THE SIZE OF MAINS
For any size system of steam or water heating the following rule will
be found entirely satisfactory for mains 100 feet long; for each 100
feet additional use a size larger ratio.
RULE.--
_r_ = (3.1416/_d_)_R_ = _a_/_r_ × 100.
_r_ represents ratio of main in inches for each 100 feet of surface;
_d_, diameter of pipe; _R_, quantity of radiation carried by size of
pipe; _a_, area of pipe in inches.
From this the following table has been constructed:
---------+---------+----------+-----------------
Diameter | Area | Ratio to | Quantity of
of pipe | of pipe | each 100 | radiation, steam
| | feet of | or water, on a
| | surface | given size pipe
---------+---------+----------+-----------------
1½ | 1.767 | 2.10 | 84
2 | 3.141 | 1.57 | 200
2½ | 4.908 | 1.25 | 400
3 | 7.069 | 1.04 | 700
3½ | 9.621 | 0.90 | 1,062
4 | 12.566 | 0.78 | 1,590
4½ | 15.904 | 0.70 | 2,272
5 | 19.625 | 0.63 | 3,120
6 | 28.274 | 0.52 | 5,440
7 | 38.484 | 0.45 | 8,550
8 | 50.265 | 0.40 | 12,556
9 | 63.617 | 0.35 | 18,100
10 | 78.540 | 0.30 | 25,300
---------+---------+----------+-----------------
FORMS OF RADIATORS
Radiators are much the same in appearance for both steam and hot-water
heating. They are hollow cast-iron columns so designed that they may
be fastened together in units of any number of sections. The sections
are made in size to present a definite number of square feet of outside
surface that is spoken of as radiating surface. The amount of radiating
surface in any radiator depends on its height and the contour of the
cross-section. The radiator sections may be made in the form of a
single column as Fig. 22 or they may be divided into two, three, four
or more columns to increase their radiating surface.
The following table, taken from a manufacturer’s catalogue, shows the
method of rating the heating capacity of a particular design. In the
table, the first column gives the number of sections in the radiator,
the second column states the length of the radiator in inches. The
columns headed heating surface give the heights of the sections in
inches and the amount of radiating surface in various radiators of
different heights and numbers of sections. As an example: This table
refers to the three-column radiators of Fig. 23. Such a radiator 32
inches high with 10 sections would contain 45 square feet of radiating
surface and would be 25 inches in length.
--------+--------+----------------------------------------------------
| | Heating surface--square feet
| +--------+--------+--------+--------+--------+-------
No. | Length | 45 in. | 38 in. | 32 in. | 26 in. | 23 in. | 20 in.
of | 2½ in. | high, | high, | high, | high, | high, | high,
sections| per | 6 sq. | 5 sq. | 4½ sq. | 3¾ sq. | 3¼ sq. | 2¾ sq.
| section| ft. | ft. | ft. | ft. | ft. | ft.
| | per | per | per | per | per | per
| | sec. | sec. | sec. | sec. | sec. | sec.
--------+--------+--------+--------+--------+--------+--------+-------
2 | 5 | 12 | 10 | 9 | 7½ | 6½ | 5½
3 | 7½ | 18 | 15 | 13½ | 11¼ | 9¾ | 8¼
4 | 10 | 24 | 20 | 18 | 15 | 13 | 11
5 | 12½ | 30 | 25 | 22½ | 18¾ | 16¼ | 13¾
6 | 15 | 36 | 30 | 27 | 22½ | 19½ | 16½
7 | 17½ | 42 | 35 | 31½ | 26¼ | 22¾ | 19¼
8 | 20 | 48 | 40 | 36 | 30 | 26 | 22
9 | 22½ | 54 | 45 | 40½ | 33¾ | 29¼ | 24¾
10 | 25 | 60 | 50 | 45 | 37½ | 32½ | 27½
11 | 27½ | 66 | 55 | 49½ | 41¼ | 35¾ | 30¼
12 | 30 | 72 | 60 | 54 | 45 | 39 | 33
13 | 32½ | 78 | 65 | 58½ | 48¾ | 42¼ | 35¾
14 | 35 | 84 | 70 | 63 | 52½ | 45½ | 38½
15 | 37½ | 90 | 75 | 67½ | 56¼ | 48¾ | 41¼
16 | 40 | 96 | 80 | 72 | 60 | 52 | 44
17 | 42½ | 102 | 85 | 76½ | 63¾ | 55¼ | 46¾
18 | 45 | 108 | 90 | 81 | 67½ | 58½ | 49½
19 | 47½ | 114 | 95 | 85½ | 71¼ | 61¾ | 52¼
20 | 50 | 120 | 100 | 90 | 75 | 65 | 55
21 | 52½ | 126 | 105 | 94½ | 78¾ | 68¼ | 57¾
22 | 55 | 132 | 110 | 99 | 82½ | 71½ | 60½
23 | 57½ | 138 | 115 | 103½ | 86¼ | 74¾ | 63¼
24 | 60 | 144 | 120 | 108 | 90 | 78 | 66
25 | 62½ | 150 | 125 | 112½ | 93¾ | 81¼ | 68¾
26 | 65 | 156 | 130 | 117 | 97½ | 84½ | 71½
27 | 67½ | 162 | 135 | 121½ | 101¼ | 87¾ | 74¼
28 | 70 | 168 | 140 | 126 | 105 | 91 | 77
29 | 72½ | 174 | 145 | 130½ | 108¾ | 94¼ | 79¾
30 | 75 | 180 | 150 | 135 | 112½ | 97½ | 82½
31 | 77½ | 186 | 155 | 139½ | 116¼ | 100¾ | 85¼
32 | 80 | 192 | 160 | 140 | 120 | 104 | 88
--------+--------+--------+--------+--------+--------+--------+-------
Fig. 22 is a radiator made up of eight single-column sections. In Fig.
23 is shown five three-column radiators, varying in height from 20 to
45 inches.
The sections of steam radiators are joined together at the bottom
with _close-nipples_, so as to leave an opening from end to end. The
sections of hot-water radiators are joined in the same manner, except
that there is an opening at both top and bottom. Fig. 30 shows the
openings of a hot-water radiator installed as _direct-indirect_ heater.
Fig. 24 illustrates a special form of radiator that is intended to be
placed under windows and in other places that will not admit the high
form. Such a radiator as that shown in the picture is often covered
with a window seat and in cold weather becomes the favorite place of
the sitting room. Another special form is that of Fig. 25. As a corner
radiator this style is much to be preferred to the ordinary method of
connection; here the angle is completely filled--there is no open space
in the corner.
[Illustration: FIG. 22. FIG. 23.
FIG. 22.--Single column steam radiator.
FIG. 23.--Three-column radiators of different heights; for steam or
hot-water heating.]
Wall radiators such as shown in Fig. 26 are made to set close to the
wall, where floor space is limited. They are particularly adapted for
use in narrow halls, bathrooms and other places where the ordinary type
could not be conveniently used.
A radiator that will appeal to all neat housekeepers is that of Fig.
27. It does not stand on the floor as in the case of the ordinary
type, but is hung from the wall by concealed brackets. The difficulty
of sweeping under this radiator is entirely avoided.
Fig. 28 is a radiator designed to furnish a warming oven for plates and
for heating the room at the same time. It is sometimes installed in
dining rooms.
[Illustration: FIG. 24.--Six-column, low form of hot-water radiators to
be placed under windows.]
[Illustration: FIG. 25.--Two-column corner radiator for steam heating.]
[Illustration: FIG. 26.--Wall form, radiator for steam or hot water.]
The ordinary method of heating by the use of radiators is known as the
_direct_ method. The air is heated by coming directly into contact with
the radiators and distributed through the room by convection. If the
arrangement is such that the air is brought from outdoors and heated
by the radiator before entering the room, it is called the _indirect_
method of heating. Such an arrangement is illustrated in Fig. 29. The
radiator is located beneath the floor, in a passage that takes the
air from outdoors and after being heated, enters the room through a
register located in the wall.
Fig. 30 is still another arrangement known as the _direct-indirect_
method of heating. The radiator is placed in position, as for direct
heating, but the air supply is taken from outdoors. The radiator base
is enclosed and a double damper _T_ regulates the amount of air that
comes from the outside. When the inside damper is closed and the
outside damper is open, as is shown in the drawing, the air comes from
outdoors and is heated as it passes through the radiator on its way to
the room. If the dampers are reversed, the air circulates through the
radiator as in the case of direct radiation.
[Illustration: FIG. 27.--Two-column radiator suspended from the wall by
brackets.]
[Illustration: FIG. 28.--Dining-room radiator containing a warming
oven.]
In the use of the _direct_ or the _direct-indirect_ method of heating
the principal object to be attained is that of ventilation, but quite
generally the passages are so arranged that the air may be taken from
outdoors or, if desired, the air of the house may be sent through the
radiators to be reheated. In extremely cold and windy weather it is
sometimes difficult to keep the house at the desired temperature when
all of the air supply comes from the outside. Under such conditions the
outside air is used only occasionally. In mild weather it is common to
use the outdoor air most of the time. The cost of heating, when these
methods are used, is higher than by direct radiation, because the air
is being constantly changed in temperature from that of the outside to
70°.
[Illustration: FIG. 29.--Ventilation by the indirect method of heating.]
[Illustration: FIG. 30.--Ventilation by the direct-indirect method of
heating.]
=Radiator Finishings.=--In steam and hot-water heating the decoration
of the radiators is a much more important item than that of a
good-looking surface or one which will harmonize with the setting.
Until recently radiator finishing has been considered a minor detail
and the familiar bronze has been looked upon as a standard covering,
while painted radiators were considered only a matter of taste. The
character of the surface is, however, the determining factor in the
quantity of heat given out by radiators. This has been determined in
the experimental laboratory of the University of Michigan by Professor
John A. Allen. Comparison was made of bare cast-iron radiators with
the same forms painted as indicated in the following table. The bare
radiator was taken at 100 per cent.; the other finishes are expressed
in per cent. above or below that of the bare radiator.
Condensing
capacity,
per cent.
No. 1, a cast-iron radiator, bare as received from the foundry 100
No. 2, a cast-iron radiator, coated with aluminum bronze 78
No. 3, a cast-iron radiator, three coats of white enamel paint 102
No. 4, a cast-iron radiator, coated with copper bronze 80
No. 5, a cast-iron radiator, three coats of green enamel paint 101
No. 6, a cast-iron radiator, three coats of black enamel paint 101
The author has stated further that, “It might be said in general that
all bronzes reduce the heating effect of the radiator about 25 per
cent. while lead paints and enamels give off the same amount of heat
as bare iron. The number of coats of paint on the radiator makes no
difference. The last coat is always the determining factor in heat
transmission.”
PIPE COVERINGS
All hot-water or steam pipes in the basement and in other places not
intended to be used for heating should be covered with some form of
insulating material. At ordinary working temperature a square foot of
hot pipe surface will radiate about 15 B.t.u. of heat per minute. To
prevent this loss of heat and the consequent waste of fuel the pipes
should be covered with some form of insulating material.
Pipe coverings are made of many kinds of material and some possess
insulating properties that may reduce the loss to as low a point as 15
per cent. of the amount radiated by a bare pipe. Many good insulating
materials do not give satisfactory results as pipe coverings because
they do not keep their shape, some cannot be considered in the average
plant because of high cost.
Wood-pulp paper is extensively used as a cheap covering; it is a good
insulator and under ordinary conditions makes a satisfactory covering.
A more efficient and also a more expensive covering that is extensively
used is that made of magnesia carbonate and known as magnesia covering.
Aside from these, other forms made of cork, hair-felt, asbestos and
composition coverings are sometimes used in house-heating plants.
In selecting a pipe covering, there should be taken into account not
only its insulating properties but its ability to resist fire, dampness
or breeding places for vermin. It rests entirely with the owner whether
he covers the pipes with a combustible or an incombustible material
when the insulating properties are about the same. Coverings made of
animal or vegetable materials under some conditions furnish a breeding
place for vermin.
Pipe coverings are made in sections about 3 feet in length and from 1
to 1-3/8 inches in thickness. The sections are usually cut in halves
lengthwise to permit being put in place. The sections are covered with
common muslin to keep the material in place and sometimes are painted
after being installed. Painting has nothing to do with their insulating
capabilities, but it preserves the cloth and makes a neat appearance.
The sections when put in place are secured by pasting one of the loose
edges of the cloth to the surface. The ends of the sections are bound
together with strips of metal. Fig. 31 shows the appearance of the pipe
when the covering is in place.
[Illustration: FIG. 31.--Pipe covering.]
Irregular surfaces like the body of the furnace, pipe connections,
etc., are insulated by coverings made from a plaster that is made
expressly for such work. It is known as asbestus plaster. The plaster
may be purchased in bulk and put in place with a trowel. As it is found
in the market the plaster requires only the addition of water to put
into working form.
The value of a pipe covering is not in proportion to its thickness.
Experiments with pipe coverings have shown that a thickness of 1-3/8
inches will reduce the radiation 90 per cent., but doubling the
thickness reduces the loss only 5 per cent. It, therefore, does not pay
to make a covering more than 1-3/8 inches thick.
=Vapor-system Heating.=--This system of heating is not greatly
different from the steam plants already described but it is operated
under conditions which do not permit the steam in the boiler to rise
beyond a few ounces of pressure. Since the plant is intended to work
at a pressure that is scarcely indicated by an ordinary steam gage, it
has been termed a _vapor system_ to distinguish it from the pressure
systems which employ steam, up to 5 pounds or more to the square inch.
The heat is transmitted to the radiators in the same manner as in the
pressure systems. The heat of vaporization of steam is somewhat greater
at the boiling point of water than at higher pressures, and the lack
of pressure, therefore, increases its heating capacity. This is shown
in the table, properties of steam, on page 3. The successful operation
of such a plant rests in the delivery of the vapor to the radiators at
only the slightest pressure and the return of the condensate to the
boiler without noise or obstruction to the circulation at the same time
ejecting the contained air.
The excellence of the system depends in the greatest measure on good
design and the employment of special facilities that allow all water
to be discharged from the radiators and returned to the boiler without
accumulation at any part of the circulating system. It requires,
further, the discharge of the air from the system at atmospheric
pressure. The system is, therefore, practically pressureless.
Various systems of vapor heating are sold under the names of their
manufacturers. Each possesses special appliances for producing positive
circulation that are advocated as features of particular excellence.
The vapor system of heating has met with a great deal of favor as a
more nearly universal form of heating than either the pressure-steam
plant or the hot-water method of heating.
Fig. 31_a_ is a diagram illustrating the C. A. Dunham system of
vapor heating. It will be noticed that there are no air vents on the
radiators. The air from the radiators is ejected through a special
form of trap that is indicated in the drawing. These traps permit
the water and air to pass from the radiators but close against the
slightly higher temperature of the vapor. This assures the condensation
of the vapor in the radiators and excludes it from the return pipes.
The water returns to the boiler in much the same manner as in the
pressure systems already described but the air escapes through the air
eliminator as indicated in the drawing. The system is, therefore, under
atmospheric pressure at this point and only a slight amount greater in
the boiler.
[Illustration: FIG. 31_a_.--Diagram showing the C. A. Dunham Co.’s
system of vapor heating.]
The water of condensation is returned to the boiler against the vapor
pressure, by a force exerted by the column of water in the pipe
connecting the air eliminator with the boiler. The main return is
placed 24 inches or more above the water line of the boiler. It is the
pressure of this column that forces the water into the boiler through
the check valve, against the vapor pressure in the boiler.
It might be imagined that the water in the boiler and that in the
air-eliminator pipe formed a “U-tube,” the vapor pressure on the water
surface in the boiler, and the atmospheric pressure on the water in
the eliminator standpipe. The slight vapor pressure in the boiler is
counterbalanced by a column of water in the eliminator pipe. It is this
condition that fixes a distance of 24 inches from the water line to the
return pipe; that is, the force exerted by a column of water 24 inches
high is required to send the water into the boiler.
The vapor pressure is controlled by means of the pressurestat, which
is an electrified Bourdon spring pressure gage, connected up by
simple wiring to the damper motor, which may be any form of damper
regulator. In residential work, the pressurestat is so connected with a
thermostat, that both pressure and temperature conditions operate and
control this damper regulator, which in turn controls the draft and the
fire.
The two instruments are so connected that if the pressure mounts to 8
ounces and the pressurestat caused the draft damper to close and the
check to open, the thermostat cannot reverse the damper, regardless
of the temperature in the room, until the pressure drops below the
limiting 8-ounce pressure. Just so long as the pressure is below 8
ounces, the thermostat is the master in the control of the dampers.
The minute that the pressure goes up to 8 ounces then the pressurestat
takes control.