hot water boiler pressure

Old 11-25-11, 09:05 AM
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hot water boiler pressure

I live in a 2 story home that heats by hot water baseboard The boiler runs at 180F but I am not sure what pressure it should run at. There is hot water getting to the 2nd floor but the baseboards do not seem as warm as the 1st floor. I think the pressure is set around 12psi>
Old 11-25-11, 10:29 AM
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The rule is 0.433 psi for every foot of elevation from the bottom of the boiler to the top of the highest heat emitter and then add 4 psi for insurance. I usually simplify it to 1/2 the height in feet (bottom of boiler to the top of heat emitter) plus a couple of psi.

This is the cold pressure. When hot the pressure will be higher. How much higher depends upon the total amount of water in the system, the temperature difference from coldest to hottest and the size of the expansion tank. The highest pressure should be equal to or less than 10% lower than the safety valve setting. For most systems this will be a maximum pressure of 27 psi.

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