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Puzzler: Condensate Return Leak, LWCO, Auto Feeder
Looking for some thoughts from the wise people
here. We have determined that there is probably a leak in our buried
condensate return piping, and I'm trying to sort out if our float-type
LWCO may also be malfunctioning.
My system: HB Smith 2500L
steam boiler with domestic hot water coil. Runs on a Heat-timer
EPU-CH. McDonnell & Miller 67 float LWCO with McDonnell &
Miller 101-A water feeder. McDonnell & Miller probe LWCO with
automatic reset, just below the bottom level of the sight glass.
Hartford loop an inch or two below the probe LWCO (seems a bit lower
Symptoms: Waking in the morning with no heat
or hot water. This only happens when night temperature does not call
for heat and the system is idle through the night. I check the boiler
and there is no water visible in the sight glass, the red light is
blinking on the probe LWCO. I fill the boiler manually by pushing the
button on the water feeder and as soon as the level reaches the probe,
the burner fires up. This takes about 2 or 3 minutes, and after another
2 or 3 minutes the water level is nearly at the "normal" line. After
this the system runs normally as long as the Heat-timer calls for heat
and cycles steam once per hour. I have put the Heat-timer in summer
mode and observed that the water level dropped about 2" over a 2 hour
Hypothesis #1: Water is slowly leaking from the
system and the float LWCO is sticking and not signaling the water feeder
to work. Water continues to drain and the probe LWCO eventually shuts
the system down. I like this hypothesis because the system seemed to
produce hot water fine for the summer and our leak is only now being
exposed because the LWCO is malfunctioning and not turning on the water
feeder. The only reason I am in doubt is that everything still runs ok
as long as there is a call for heat. We know there is a leak, so at
some point the float LWCO must be triggering the water feeder. Is it
possible that the flow of water through the return piping during steam
production slows the leak enough to not require makeup water? Or maybe
just the way water is moving through the system prevents the float from
sticking? Also note: when the system is producing heat, opening the
blowdown valve on the float LWCO does actually trigger the water feeder.
#2: At some point during the night, water leaks quickly from the
system. The float LWCO signals the water feeder to turn on, but it
cannot keep up, and eventually the float LWCO turns everything off,
including the water feeder. Water level continues to drop until the
probe LWCO also activates (Do these LWCOs turn off the water feeder if
the cutoff water level is reached?). I have doubts about this
hypothesis as well because I would think that the float LWCO would need
to be reset by bringing the water level back to near normal before the
system would turn on again. As I said before, the system turns back on
as soon as water reaches the probe LWCO, which is well below the float
Thank you all for reading and I hope you can help me solve this puzzler.