Posted by Tom S. on May 10, 2001 at 18:46:32:
In Reply to: pressure build up posted by cory n on May 10, 2001 at 17:29:55:
Sounds like one of a couple of things. First is the pressure reducer (or feed valve) operating properly and NOT over feeding the boiler ? 2nd, is the expansion tank or diaphragm tank waterlogged? If it is, the expansion water will have nowhere to go except out of the relief valve. If its a diaphragm tank gone bad it needs to be replaced as the diaphragm will have burst within the tank. If its an actual steel tank, it needs to be drained to make some room for expansion water. I would almost bet on that. If its not any of those things the system may be airbound causing excess pressure. You shouldn't need a manufacturers manual to figure this out. Its all pretty common stuff. If it has happened before or happens again it may be a sign of something else wrong systematically. Possibly a mis-located feeder? Is the feed line tied in to the inlet side of the circulator? The feed MUST be installed at the point of zero pressure difference to operate properly. If its a diaphragm type tank, the pressure in the tank has to coincide with boiler pressure. Diaphragm tanks are factory charged to 12 p.s.i. If the system has 18 or 20 p.s.i. on it it may cause the tank to fail prematurely.The tank may be pumped up to the pressure which your system is operating with a bicycle pump and checked with a tire gauge. If you have little or no experience you should leave it to a COMPETANT service tech. Good Luck !