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Triangle tube prestige excellence pressure increasing.

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dahlenburg
dahlenburg Member Posts: 7
I have the triangle tube prestige 110 excellence and the boiler pressure keeps increasing. This is the combi boiler with DHW. First noticed the floor was wet under the pressure relieve valve. Checked the pressure and found it was at 30. Drained some water to get the pressure down below 15 and found that after 2 days it was back at 30 again. Thinking the pressure valve on the fill line might be bad I shut off water to the boiler fill line and the pressure continues to rise. It is a very slow rise and usually takes 24-48 hours to get back to 30 after dropping it to 15. I have lowered the pressure 7-8 times over the past couple of weeks now all with the supply line shut off to the boiler. I have read that it could be the DHW leaking into the boiler system some place. Is there a way to check for this?

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  • Jamie Hall
    Jamie Hall Member Posts: 23,426
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    Is there domestic water being heated by the same boiler? If so, then indeed it could be leaking in, since the domestic water is at much higher pressure.

    The way to check is first to verify that what you have already done really has been done: that the manual valve feeding water through the pressure regulating valve is really truly shut off. If it's a ball valve (quarter turn) it probably is, but worth looking at again. If it's a glove valve or gate valve, maybe not. They can and do leak.

    Then, once you are happy that you really have shut off the manual feed, shut off the domestic hot water input line. Verify that that really is shut off: open a hot water tap somewhere in the house, and you should get no flow. If you do get flow, there may be a mixing valve somewhere in the system which allows flow from the cold line to the hot line and you'll have to isolate that.

    Then see what happens...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    kcopp
  • dahlenburg
    dahlenburg Member Posts: 7
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    It does have the DHW on it. I will double check the ball valve as well as turn off the hot water supply line when I get home tonight and report back what I find.
  • SuperTech
    SuperTech Member Posts: 2,185
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    It sounds like by shutting down the water to the heating side of the system you have confirmed the source of your problem. Have you made sure your increase in pressure isn't due to a failed/waterlogged expansion tank?
  • dahlenburg
    dahlenburg Member Posts: 7
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    SuperTech said:

    It sounds like by shutting down the water to the heating side of the system you have confirmed the source of your problem. Have you made sure your increase in pressure isn't due to a failed/waterlogged expansion tank?

    I did check the expansion tank. I may be wrong but with the supply line shut off and draining water from the system several times to drop the pressure the expansion tank shouldn't be an issue? The extra water has to be coming from some where.
  • Zman
    Zman Member Posts: 7,572
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    You likely have a pinhole leak in the heat exchange between the boiler water and domestic water.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    SuperTechkcopp