National Oilheat Research Alliance 9
Thermostatic radiator valves (TRV) are
available that, in conjunction with a standard
vent, enable each heat emitter to be individually
controlled. TRVs control the flow of steam
into the heat emitter by sensing the temperature
of room and opening or closing as required.
Figure 7
Wet return - The portion of the return piping
that is filled with water.
Dry return - The portion of the return piping
that is not filled with water.
“A” dimension – To allow condensate to
return to the boiler, the lowest steam carrying
pipe MUST be at least 28" above
the boiler’s normal water line
for most systems. Counter-flow
systems and boilers with a false
water line piping arrangement
installed do not require a 28" A
dimension.
Hartford Loop – The
Hartford loop prevents physical
damage and personal injury
by preventing water from being
pushed out of the boiler and up
the return piping. It also prevents
a low water condition if the
return piping develops a leak.
Figure 7.