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# Boiler Pressure question

Member Posts: 14
Fill valve on my heating boiler failed and my pressure relief valve opened at about 31 psi. Guy replaced fill valve, and pressure relief valve. Then "reset" pressure to what appears to be about 14 or 15 psi. My pressure stays at this level no matter if water temp is cold or peak hot (as everyone knows to read the tiny gauges on the boiler is difficult to get exact readings. The gauge starts at 0, then has 2 additional lines, then reads 20. The "arrow is on the 2nd line before the 20 line. So 0, then line, then line, then 20.) My 2 story contemporary has 8 ft ceilings in basement then another foot of floor joist space, 8ft ceiling on first floor then another foot of floor joist space, to bottom of 2nd floor baseboard. So if I calculate correctly I have 8ft plus 1(basement) , another 8ft plus 1(1st floor), then 1ft to top of 2nd floor baseboard. Total 19 feet. I understand to calculate needed pressure you take total feet and divide it by 2.31. But 19 divided by 2.31 is only 8.22psi at cold temp. My boiler pressure stays basically constant no matter if hot or cold at about 14 or 15 psi, is this too low, too high?

• Member Posts: 1,989
The idea there is to keep a minimum of 12 psi in the system regardless of height, and add more if necessary for higher radiation. You only need 8.22 psi to lift water from the basement floor to the highest point, and it's always good to have some extra at the highest point so it doesn't pull a vacuum in the event of minor water loss, so 12 (or 14-15) psi is perfect as long as the expansion tank was properly charged to accommodate the slightly higher water pressure (most come pre-charged to 12 psi). Seeing as your pressure remains the same regardless of temp, I'd wager a guess that the technician properly charged the expansion tank because that's exactly what it's supposed to do. The height measurement should be from the pressure gauge height, not the floor, but either way I think what you have is just right.
• Member Posts: 23,927
You're fine. Though I'd expect the pressure to rise slightly when the boiler is hot... but that's most likely the silly gauge they give you.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 7
Are you reading that right my boiler turns off at 6 psi
• Member Posts: 23,927
Your boiler is controlled by pressure? This is a hot water system? Pressure should have nothing to do with it. What I read you to say is that you think your system pressure is "stays basically constant no matter if hot or cold at about 14 or 15 psi:".

Now you say it shuts off at 6 psi? I'm confused.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
• Member Posts: 11,160
Do you have a Munchkin boiler?
Some of them have a pressure switch that will throw up a code and not run.
• Member Posts: 14
I did not say my boiler turns off at 6psi. That was someone elses post.