HOT-WATER HEATERS. INSTANTANEOUS COIL AND STORAGE TANKS. RETURN
CIRCULATION, HOT-WATER LINES AND EXPANSION
The problem of supplying hot water to plumbing fixtures is one that
has required years of study. Each job today demands considerable
thought to make it a perfect and satisfactory hot-water system. We
will find installations today where the water is red from rust,
where there is water pounding and cracking. There are also jobs
where the fixtures get practically no hot water. As each job or
individual building has its own peculiar conditions, they must be
solved by the designer or the mechanic, using the fundamental
principles of hot-water circulation. We must first know how much
hot water is to be used, also the location of the outlets and the
construction of the building; then the size of the pipes and the
size of the tanks and their locations can be settled. If the job is
a large one, a pump may be employed to insure the proper
circulation. After this the pipe sizes and connections can be
worked out. The one great enemy of hot-water circulation is air.
Therefore, no traps or air pockets should ever appear in the piping
system. The boiler, as it is often referred to, is the hot-water
storage tank. A copper or iron tank holding sufficient water to
supply all fixtures, even when every fixture demands a supply at
the same time, is installed in a convenient place and the heating
arrangement connected with it. A thermostat can be placed on the
system and the temperature of the water controlled. According to
the size of the building the problem of furnishing the plumbing
fixtures with hot water increases.
METHODS OF HEATING HOT WATER.--There are a number of ways of
furnishing hot water. Some of the installations are listed below.
A cast-iron or brass water back is placed on the fire pot of a
stove or furnace. A separate stove with the fire pot and water
jacket is used. A coil of steam pipe is placed inside a hot-water
boiler or tank. Gas coil heaters are connected with hot water
storage tank, also gas coil instantaneous heaters are connected
with the piping direct.
Combinations of the above systems are in use and serve the purpose
for which they are intended. For instance, the tank can be
connected with a coal range and a gas coil heater, heat being
furnished by the range alone or the coil heater alone, or both can
be used at the same time. This combination can be connected with
the furnace in the cellar, and during the winter months, when the
furnace is in use, the water can be heated by the furnace coil. In
warm weather, when the furnace is out, the range can supply the
necessary heat. In hot weather the coil gas heater can supply the
heat.
CONNECTIONS OF TANK AND HEATING APPARATUS.--The ordinary house
boiler or hot-water storage tank has four connections, two on top,
one on the side, and one on the bottom. The top connections are
used for the entrance of cold water into the tank and for the
supply of hot water to the fixtures (see Fig. 71). The cold-water
inlet has a tube extending into the tank below the side connection.
This tube has a small hole filed in it about 6 inches from the top.
This hole is to break any syphonic action that may occur at any
time. The side connection is for the connection of the pipe coming
from the top of the water back. The bottom opening in the tank is
for the connection of the pipe coming from the lower water back
connection, also for draining the boiler. The circulation of the
water can be followed thus: cold water enters the boiler in the
tube and discharges into the boiler below the side connection. From
here it flows out of the bottom connection into the water back,
through the upper connection into the boiler, through the side
opening, then to the top of the boiler and out to the fixtures
through the fixture supply opening.
[Illustration: FIG. 71.--Storage tank, and coil heater with
thermostatic control valve.]
Fig. 69 shows a thermostatic control valve attached to the bottom
of a heater coil, and at the side of storage tank. The best
arrangement is at the bottom, for it does not shut off the gas
supply until the boiler is full of hot water.
CONNECTING TANK AND COIL GAS HEATER.--The boiler and the coil gas
heater have a different connection. The bottom of the tank and the
bottom of the heater are connected. The top of the heater and the
top of the boiler are connected. The accompanying sketch shows how
this connection is made. If the tee on the top of the boiler into
which the gas-heater connection is made is not the first fitting
and placed as close to the outlet as possible, the water will not
circulate freely into the boiler. This connection according to the
drawing should be studied and memorized.
[Illustration: FIG. 72.--Instantaneous gas heater. Showing
circulation heater or booster.]
INSTANTANEOUS GAS-HEATER CONNECTIONS.--An instantaneous gas heater
is placed in the basement. The copper coil in it is connected at
the bottom with the cold-water supply and the top outlet of the
coil is connected with the hot-water system of piping. There is no
need of a storage tank with this heater. When a faucet is opened in
any part of the hot-water piping system, the water passing through
the water valve at the heater causes the gas valve to open so that
the whole set of burners in the heater is supplied with gas, and
the burners are lighted from a pilot light. When the faucet is
closed, the gas supply is shut off and the burners are put out. The
pilot is lighted all the time. Space will not permit going over
these connections in detail. It is a large field and requires
considerable thought.
SAFETY AND CHECK VALVES.--When a meter is used on a water system,
the water company demands that a check valve be placed on the
hot-water system to prevent the hot water from being forced back
into the meter in case the pressure got strong enough in the
boiler. If a check valve is used for this purpose, or for any other
purpose, a safety valve must be placed on the boiler piping system
to relieve any excessive pressure that may be caused by having the
check valve in use. There is today, with meters of modern type, no
reason to use a check valve or a safety valve. If an excessive
pressure is obtained in the boiler, it is relieved in the water
main.
When water is heated, it expands. If the heat becomes more intense
and steam is formed, the expansion is much greater, and some means
must be provided to allow for it. This expansion can be allowed to
relieve itself in the water main as explained above. When a check
valve is placed on the piping, this means of escape is shut off and
a safety valve must be employed. Without these reliefs, the
pressure would be so great that an explosion would result. When
steel pipe and steel boilers are used for storage tanks and
connections, the pipe and tank will shortly start to rust and parts
of the piping are stopped up with rust scales. The water also
becomes red with rust when the water becomes hot enough to
circulate. When the pipes are stopped up, steam is formed and a
snapping and cracking sound is heard. To avoid these conditions,
the piping should be of brass or lead and the storage tank should
be of copper. The installation cost of brass and copper is greater
than steel, but they will not have to be replaced in two or three
years, as is the case with other material. A valve should be placed
on the cold-water supply to control the entire hot-water piping
system. A pipe with a stop cock should be placed underneath the
boiler and should extend into a sink in the basement so that the
boiler can be drained at any time for cleaning or repairs.
CONNECTING WITH FIXTURES.--To have all fixtures properly supplied
with hot water it is necessary to run what is termed a circulating
pipe. This circulating pipe is a circuit of pipe extending from the
top of the boiler to the vicinity of the fixtures and then
returning to the boiler and connecting into the pipe leading out of
the bottom of the boiler. From this circuit all branches are taken
to supply all fixtures requiring hot water. This circulating pipe
has hot water circulating through it all the time. Therefore the
fixtures are supplied with hot water very quickly. The circulating
pipe and its branches are run without any traps or air pockets.
[Illustration: FIG. 73.--Expansion loop. Four 90 deg. ells.]
[Illustration: FIG. 74.--Expansion loop. Five 90 deg. ells.]
[Illustration: FIG. 75.--Expansion loop. Six 90 deg. ells.]
When running the piping, it should be borne in mind that not only
does the water expand when heated, but the pipe expands also.
Therefore due allowance must be made for this expansion. The long
risers should have an expansion loop as shown in Figs. 73, 74 and
75. There are installed on some jobs what is known as an expansion
joint. This will allow for the expansion and contraction of the
pipe. The writer's experience with these joints has not been very
satisfactory. After a while these joints begin to leak and they
must have attention which in some cases is rather expensive. An
expansion loop as shown in the sketch, made with elbows, will prove
satisfactory. If the threads on the fittings and pipe are good, no
leak will appear on this joint.
All gas heaters must be connected with a flue to carry off the
products of combustion.