One Pipe Pumped Return Systems
One pipe parallel upfeed pumped
return system (Figure 5)
To convert from a one pipe gravity system
to a pumped return this system had the heat
emitter air vents removed, and an F&T trap,
strainer, condensate receiver and pump installed.
• The F&T trap must be installed at the end
of the main.
• The condensate tank/pump must be properly
sized. (See Chapter 7—Sizing a
Condensate Return Unit)
• The return piping from the trap must slope
downhill to the condensate tank.
• A check valve must be installed as shown
to prevent water from being pushed back to
the tank.
• A square head cock or a balancing valve
must be installed to throttle the feed
pump’s flow rate to the boiler. An improper
flow rate can cause water hammer and
water level fluctuations in the boiler.
• The main vent is optional (but recommended)
on these systems because F&T
traps allow air to escape.
26 National Oilheat Research Alliance
Figure 5