National Oilheat Research Alliance 29
Parallel Downfeed Pumped Return System
Two Pipe Pumped Return
Systems
See following pages, Figures 7 & 8
• In a two pipe pumped return
system there are no main vents
or heat emitter air vents.
• The steam main must slope
downhill toward the F&T trap at
least 1" per 20'
• Radiator valves can be throttled
to regulate the heating rate.
• Steam enters the top of a heat
emitter and both condensate and
air leave the heat emitter through
a thermostatic trap located at the
bottom of the opposite end of the
emitter.
• A typical 2 pipe pumped return
system should have the pressuretrol
set to cut in a ½ psi and
cut out at 2 psi. Higher pressures
are not required unless the system
includes heat exchangers or
unit heaters.