Boiler temp and pressure problems

Old 10-26-05, 05:59 PM
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Boiler temp and pressure problems

Purchased a 1920's Victorian with hot water heat system that heats first and second floors. The entire system runs off one thermostat on the first floor. It's an American Standard Boiler, but I'm not sure of the year. Ayway, here the problem..... whenever I turn the boiler temp up above 140 degrees the pressure gauge on the boiler goes up near 50 pounds, also the system pressure gauge rises to 30 pounds and will often cause the relief valve to start spitting water. So here is my questions?
1 - At what temp should a hot water system operate normally
2- Why an I getting this pressure build up
3- Is there any way a DIY can fix it

Any help would be appreciated, Thanks
Old 10-26-05, 07:23 PM
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Low temp - high pressure

It sounds like your expansion tank may be flooded or nearly so. If it is a conventional tank with a hose bib on it, there should be some sort of shut off valve between the tank & the boiler. Close the shut off valve, attach a hose to the hose bib, open the hose bib, & drain the tank completely. Once drained, reverse the process, opening the shut off slowly while trying to maintain about 15 psig on the boiler.

"Normal" temperature for a hot water boiler is about 180.

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