over pressuring boiler

[jbrock]

I have a old American Standard gas fired boiler that is giving me fits!! It keeps over pressuring and blowing the relife valve at 30psi. Ive tried to bleed the baseboards, but get very little air out of them. The expansion tank is a old metal on stuffed in the raffters it does have water in it. Should I drain it? what can i do to stop it from blowing th prv? One more question what temp should the boiler heat up too. Thanks any help is a great!!

[Ed Imeduc]

lot is in just what you have there or want. Yes drain the expansion tank. That should stop it from poping the PR valve. If not the auto water fill can be screwed up and not work right. They come set for 15 psi .Thats about what you should have for 1 floor. Most boilers are set for 160o on and 180o off.

ED ;)

[arkayassoc]

Most likely, you have too much water in the system. Close the feed valve so no more water can be added. Drain the expansion tank. You may need to drain additional water out of the boiler, but we need to know what the pressure is after you drain the expansion tank.

How many floors are you trying to heat from the boiler to the top floor? That will help us determine what the correct pressure should be.

[jbrock]

Im heating two floors. Ill drain the expansion tank and see what happens and get back to you!

[jbrock]

I started with 22psi Shut off incoming valve for tank and drained about 4 gallons of water!! close valve. Opened incoming valve dropped to 4 psi. Fill started to fill on its own and came up to 14psi have to see what happens from there. What do you think?

[Ed Imeduc]

When it said 14 lb psi do you get water out of the top bleeder??? Think this way forget the gauge psi. The boiler has to be just so you get water out of the very top bleeder and that is the psi you need on the boiler


ED ;)

[jbrock]

sorry i havent got back to you. Been busy! Well boiler still over pressure and blows prv. when you say top bleeder screw do you mean on the boiler the closest one i could find is one the air scoop.And yes i get water out of it. Maybe i need to drain whole system and start over, drain expansion tank and boiler? Could bad running pump cause a problem like im having? My pump does leak a little. Well once again thanks for any help!!

[arkayassoc]

The top bleeder screw Ed was referencing was the bleeder on the radiator at the highest elevation and furthest point from the boiler.

Your guage could be wrong, and you might have more than 14 psi. Like Ed said, all you need is enough pressure to get water to the furthest radiator.

The pump is a circulating pump, not a positive displacement pump, so it is not contributing significant pressure to your system.

You probably need to drain water from the expansion tank again, and reduce the pressure on the auto-fill valve, so it does not go up to your current 14 psi guage reading, and see if you still have a problem.

[KField]

When you drain the expansion tank, you MUST drain all the water out. What you are really doing is filling it with air. If you don't take every last drop of water out of it, you do not leave enough room for air. This will make the problem worse than before. It can be a pain in the neck to drain a tank with no air inlet on it, especially if you hang a drain hose on it. It usually works best on that kind of setup if you use a bucket. Once the tank is totally empty, close the drain valve and open the valve between the tank and the system and let it refill. Everything should work OK after that.

Ken