MRnice wrote:
My Dunham/Bushe residential boiler is a hot water boiler with a forced
hot air central heating system. It has been running at a high pressure
(30 lbs.) and this is causing the pressure relief valve to release
water. I drained the expansion tank (which was full) by shutting the
feed and opening the drain valve. It is an old system with no
compressed air in the tank, which I believe does not have a bladder in
the tank. It does have a shut off valve below the inlet to the tank
and a drain valve with a hosecock connection on the opposite side. The
inlet and drain are both on the bottom of the tank. After I drain it
the system functions fine for a day until the pressure builds up and
the tank is full again. I think I am bleeding it right, or am I? The
pressure relief valve does go off due to the high pressure, but does
seem to seat well after the pressure goes down. After reading some of
the postings on the board, I also thought that the temperature setting
on the aquastat may be too high. It is currently set at 160 as the
high and 130 as the low with a 10 degree differential. What would the
correct temperature setting be?

I would appreciate any assistance. Thank you, MRnice


I think you have a good understanding of the system and
how that ancient exp tank works. Should work with those
temp settings OK.

It's possible that an automatic fill valve from the
incoming water supply is leaking and refilling the system,
causing the high pressure. Find a shutoff valve and close
it to find out.

Jim