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Thread: New boiler issuse

  1. #1
    DIY Junior Member 42flathead's Avatar
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    Default New boiler issuse

    Boiler pressure gradually rises to 30 psi. 2 zones are baseboard and 1 zone is in slab radiant heat. I have a spiro vent set up. My relief valve keeps popping off. The boiler ran fine until I hooked up the radiant heat. I am using a mixing valve to control the radiant heat temp. Do you think it may have air in the radiant system.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Check the expansion tank. Make sure it isn't waterlogged or the air pressure isn't too low (note, you can't check it with the system under pressure, it will just read that rather than the static air pressure). If you had excessive air, the water probably wouldn't circulate. If the radiant stuff gets hot, you should be okay in that regard. If you don't have an expansion tank, someone messed up, add one!

    If that isn't it, it could be the autofill valve, or the fill valve may be leaking.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member 42flathead's Avatar
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    I have an expansion tank. I put in the deluxe spiro vent tank and auto fill valve. It was fine until I tied in the radiant. after running the radiant portion of the system, is it possible I would have to bleed the 2 loops again? If so do I isolate the other zones?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    Air would keep it from circulating and heating those zones, not increase the pressure. The tank could be bad or lost its precharge (nominally around 15#). The pressure only goes up if the non-compressible water has no place to go or you have additional water being introduced (through the autofill, or fill valve). If there were air in the system, that would provide a place for the water to expand, and thus keep the pressure stable unless, the water isn't circulating at all, and the boiler is overheating, creating steam, which is MUCH larger volume than the air or liquid water. But, if that happened, other safety features should shut it down.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    In the Trades Tom Sawyer's Avatar
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    shut the water feed to the boiler off. see if the pressure raises. If so do you have a tankless coil in the boiler or an indirect water heater? Either of these can cause the problem if there is a leak in them.

  6. #6
    Engineer Furd's Avatar
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    The boiler ran fine until I hooked up the radiant heat.
    If you can valve off the radiant see if the system again works okay. If yes then the expansion tank is probably too small for the total amount of system water. You can either change to a larger expansion tank or add another in parallel with the existing tank.

  7. #7
    DIY Junior Member 42flathead's Avatar
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    I shut off the boiler feed hand valve and the pressure stayed at 15-18lbs. on the guage. I turned the temp down from 190 to 180 degrees. I didn't know if the temp had anything to do with the increased pressure. Sounds like the new auto fill valve has a little dirt or something in it causing it to leaking by? I re-opened the hand valve and the pressure came up slowly. Either I take off the top of the auto fill valve and clean it or replace it. The system is all new. It may be easier to take it apart and clean it.

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    Not sure how easy it is to clean or repair the autofill valve. Out of curiosity, what brand is it? Where does it say it was made?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9
    In the Trades Tom Sawyer's Avatar
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    Nope, bad autofill change it. If it's new, it's warrantied.

  10. #10
    DIY Member tk03's Avatar
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    There is a strainer in them can be blocked, other than that replace. Might try manually opening and sometimes they work after that due to flushing.

  11. #11
    DIY Junior Member 42flathead's Avatar
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    It's a watts auto fill valve

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