There are two methods of warming by steam heat—one with live steam
direct from the boiler, and the other with exhaust steam. These two are
frequently carried out in combination, and in fact generally so where
exhaust steam is used at all for warming.
In nearly all manufacturing establishments, office buildings, etc., the
exhaust steam produced will very nearly, if not quite supply sufficient
exhaust steam to furnish all the heat required for heating the building
during average weather, although in extremely cold weather, a certain
amount of live steam might be necessary to use in connection with the
exhaust to supply the required amount of heat.
A simple and convenient device operating upon the suction principle
has been found to be most efficient. By this the exhaust steam is
drawn almost instantly through the most extensive piping; preventing
condensation, freezing and hammering, after which it is condensed and
purified, and fed back into the boiler by the means of a reciprocating
pump.
It is claimed that a given quantity of exhaust steam can be circulated
by this vacuum system and uniformly distributed through double the
amount of heating pipes than could be accomplished by the same quantity
of exhaust steam when forced into the heating system by pressure.
Fig. 144 is a well-tried system of heating by exhaust steam in which
“7” represents the steam exhaust pipe, with “6” showing back pressure
valve with weight to adjust amount of back pressure; “4” “4” are steam
supply pipes to radiators; “5” “5” are risers; “9” “9” are condensation
return pipes from the radiators; “8” is the pressure regulating
valve from the boilers. Fig. 144 may also be said to represent the
general method of piping used in steam and hot water heating, which is
difficult of illustration owing to the fact that each locality where it
is used requires a different adaptation.