boiler pressure gain

Helgy_3

Happy New Year to everyone.....

Working on a 20yr. old Peerless hot water boiler. Problem is as the boiler heats up the pressure gain goes way up until the saftey pops. Setup is two story home all cast iron radiators. Each one having it's own air bleeder. Boiler has a rafter tank w/ tank valve. I filled the system bled the air from each radiator. Made sure I had air in rafter tank via tank valve bleeder. Starting pressure of about 14 lbs. Start system up and at about 140 degrees it's ready to blow it's safty valve. What am I missing here. Any help would be great..

Thanks, Helgy

Steamhead

Drain the tank completely

by closing the valve in the line to the tank, then opening the drain and bleeder. Then put the tank back in service. That bleeder on the tank is probably connected to a small tube that goes up to the top of the tank, so even if there was not enough air in the tank you would still get air at the bleeder.

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Helgy_3

tank valve

Yes it is one of those tank vavles that you can bleed. After turning off the inline valve to the rafter tank and bleeding the water down till you get air. Do you do the above while the boiler is at operating temp or cold.

Steamhead

Shouldn't matter, but

I'd shut off the power or turn the thermostat way down so the burner doesn't fire while the valve to the tank is off.

Be sure to drain the tank completely. This can take 30 minutes or more on larger tanks. Make sure all the water is out before you put the tank back in service.

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