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