A thermostat is a device
used to control the amount of heat developed in a furnace.
Thermostats can be used with hand-fired
heating equipment as well as automatic types, such as coal stokers,
oil burners, and gas.
As has been pointed out, a thermostat
controls the amount of heat developed in a hand-fired furnace by
regulating the position of the dampers.
On automatic coal stokers, the thermostat
controls the position of the drafts as well as the amount of fuel
fed into the furnace by the stoker. On oil and gas burning equipment,
it controls the flow of fuel into the burner.
Basically, a thermostat is an electric
switch actuated by a change in temperature.
The thermostat is set for any temperature
desired, and when the house temperature falls below this setting, the
thermostat automatically makes the changes necessary in the heating unit
to produce more heat. When the house temperature rises to that set on
the thermostat, the heat is automatically reduced.
There are many kinds of thermostats. The
simple ones are set by hand, while the more complex have built-in clock
mechanisms and can increase or decrease the heat at the hours for which
they are set. This is particularly welcome on cold winter mornings, for
the house can be comfortably warm by the time the household arises.
Near a radiator or exterior door,
like above, is not good.
Because the action of the thermostat
depends upon the temperature of the air around it, some thought
must be given to its location. If the thermostat is placed near
a radiator or hot air register, it will naturally heat very quickly
and reduce the fire in the furnace before the air in the rest of
the house has reached the desired temperature.
Likewise, if it is too near the floor,
where air is cooler, or near an outside door where it will be constantly
chilled by drafts, the thermostat will keep the heating unit burning
high even though the rest of the house is too warm. In some cases,
where the thermostat has been set on the wall directly over an electric
light fixture, the heat produced by the light bulb is sufficient
to cause the thermostat to lower the fire.
When a thermostat is so located that
it does not give a true indication of the temperature in the house,
it must be moved, or continually set at a different temperature
to compensate for the inaccuracy.