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Thread: High Boiler Pressure

  1. #1
    DIY Junior Member E_Chorn's Avatar
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    Default High Boiler Pressure

    Since I'm pretty new to the DIY'ing, I was hoping someone would be able to help me out...

    I have in-floor heating as my primary heating system, which also heats my DHW through an indirect. The boiler has been sitting around 33-35psi for the last little while, causing my PRV to release water on a semi-regular basis. I originally thought my expansion tank was the issue. It's 9 years old and was full of water. I replaced it a couple weeks ago, and the boiler pressure evened out at around 20psi.

    Now, about 2 1/2 weeks later, my PRV is leaking again. Was hoping it was just a faulty valve after the workout it got before, unfortunately I checked my boiler, and the pressure is back up to ~33-35psi. Any thoughts or ideas on what could be going wrong here?

  2. #2
    In the Trades Tom Sawyer's Avatar
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    Drop the pressure to 15 lbs and shut off the water feed. If the pressure climbs you have an expansion tank issue. If it falls, you have a leak.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  3. #3
    DIY Junior Member E_Chorn's Avatar
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    I can't seem to get the pressure to drop... before I could get it to drop by releasing water through the PRV. Now it's staying consistent at above 30... any suggestions?

    Also; the tank was pressurized at 15 when I bought it. Checked on it now, and the pressure on the tank is sitting at around 26
    Last edited by E_Chorn; 09-26-2011 at 05:36 PM.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    When the system is closed, the tank will read the same as the water pressure. You can only preset that pressure when there's no water pressure on the other side. Did you shut the autofill valve out of the circuit? If it is leaking, it will keep the pressure high. If your water pressure gauge is not reading the same as the expansion tank, then one or the other gauges is wrong. Other causes of high pressure could be a leak in the IWH heat exchanger.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member E_Chorn's Avatar
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    Quote Originally Posted by jadnashua View Post
    When the system is closed, the tank will read the same as the water pressure. You can only preset that pressure when there's no water pressure on the other side. Did you shut the autofill valve out of the circuit? If it is leaking, it will keep the pressure high. If your water pressure gauge is not reading the same as the expansion tank, then one or the other gauges is wrong. Other causes of high pressure could be a leak in the IWH heat exchanger.
    I shut the autofill off, and the pressure did come down a little bit. Is this pointing toward a leak in the system like Tom Sawyer indicated above?

    Also, I just had the indirect hot water tank replaced about 6 months ago. You think there may be a leak in the new tank?

  6. #6
    In the Trades Tom Sawyer's Avatar
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    Very possible that there is a leak between the coil in the indirect and the potable supply. To test. Shut off boiler feed , drop the pressure in the boiler to 15 lbs and see if it climbs again. If it does, the only place it can be getting pressure is through the indirect's coil.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    What kind of valve is it that disconnects the autofill? If it's not a ball valve, that could be leaking. The pressure will change slightly based on the temperature of the water in the system...the expansion tank helps to moderate that quite a bit, but it can still change (but not by much).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #8
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    If you had your indirect changed out, you know a professional. There is your answer.

  9. #9
    DIY Junior Member E_Chorn's Avatar
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    It's actually a cross connection (Watts 009) and a regulator (Watts 1156F) that are controlling the water entering into the system.

    I'm leaning more towards there being a leak somewhere in the system. After I turn off the supply, the system seems to lose water, and fills up with air. I'm really hoping it's not a pipe in one of the zones, but I'm thinking I should start shutting off zones (there are 4) one at a time and testing out whether the system continues to take on air with each of them shut off.

  10. #10
    DIY Junior Member E_Chorn's Avatar
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    Quote Originally Posted by BadgerBoilerMN View Post
    If you had your indirect changed out, you know a professional. There is your answer.
    I got hosed by the company that changed out my indirect. I would rather not go back to them.

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