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Autofill valve stuck open causing too high of pressure.

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by wrightk20, Nov 30, 2012.

  1. wrightk20

    wrightk20 New Member

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    Got my new expansion tank installed yesterday and everything looked good. Pressure was around 15psi at 190 degrees. Went to check it before going to bed and the pressure gauge was over 40 psi! I drained probably 20 gallons of water out of the system to get it back down to a normal range. Right now i have the ball valve going to the auto fill valve shut off and everything is looking good when i got up this morning. Anyone ever have an autofill valve stick open like this? Do i even need to have an autofill valve in the system? This wouldn't have anything to do with me installing an over sized expansion tank would it? I have a sx160v installed with only 165 gallons of water in the system. I went oversized so that i could add storage later. Any opinion would be appreciated. Thanks, Kevin.

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  2. maple1

    maple1 Minister of Fire

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    Should have nothing to do with how big your expansion is - sounds like it must have stuck.

    I have autofill plumbed into mine, but it's always valved off. If my system gets low, I open the valve & close it again when its back up to pressure. I've only done that once.

    Maybe take it apart & clean it? Even though mine never stuck, it was pretty cruddy inside when I made my system changes this fall - looked like water wouldn't even make it through it. It cleaned up pretty good, with a little work. Likely a piece of dirt got stuck in the seat or something.
  3. wrightk20

    wrightk20 New Member

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    Yeah thats what i was thinking. Now with the pressures looking good now i will probably just wait till i shut it down this spring. Do you know of a good boiler gauge that is accurate? The one in my basement is a weiss instrument one and the pressures on it don't match the boiler that is outside. My boiler is uphill a little from the house but i don't think that would cause a 5-10lbs pressure difference would it?
  4. peakbagger

    peakbagger Minister of Fire

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    I have had it happen once or twice. They tend to fail open so the boiler always has water and squirts it out of the relief so people deal with it. If they failed closed, most folks without a low water cut would trash their boiler. The internals get old and brittle. You in theory can rebuild them but I have never found and kit and just replace them. The usually die right when you are doing a fast fill after draining the system.
  5. wrightk20

    wrightk20 New Member

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    The bad part is that its only the 3rd heating season on this thing. I can't see it being old and brittle. I will have to investigate come spring and see whats holding it open.
  6. ozzie88

    ozzie88 Member

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    Do you have a DHW coil systom that may be leaking inside causeing more boiler preasure?
  7. wrightk20

    wrightk20 New Member

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    I have a sidearm on my water heater, but i shut off the ball valve going to the autofill valve and that has solved the problem for now.
  8. Bob Rohr

    Bob Rohr Minister of Fire

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    What brand and model fill valve do you have? Many of them have a fast fill lever or arm, maybe you have it locked in fast fill position? If so it will go to the same pressure as the inlet side.
  9. wrightk20

    wrightk20 New Member

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    I believe it's a watts brand with a backflow preventer.
  10. Floydian

    Floydian Feeling the Heat

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    I am curious as to why your gauge even read 40 psi. Shouldn't the pressure relief valve be doing it's thing at 30 psi?

    Noah
  11. wrightk20

    wrightk20 New Member

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    The valve at the stove was blowing. The gauge that I have in my basement differs from the one on my boiler by 5-10 psi.
  12. Floydian

    Floydian Feeling the Heat

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    I see. So, assuming the gauges are accurate, that means your boiler is somewhere between about 11 to 23 feet above the gauge in your basement. Does that sound right?

    Noah
  13. wrightk20

    wrightk20 New Member

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    I would say that is correct. So your saying that I actually had over40 psi in my system?
  14. wrightk20

    wrightk20 New Member

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    I always figured that the gauge wasn't very accurate.
  15. Floydian

    Floydian Feeling the Heat

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    I would say its possible the lowest part of your system could see pressure that high. It all comes down to the elevations involved and maybe a few more factors that I don't understand. Hopefully some more knowledgeable folks can offer some input on this.

    Noah
  16. wrightk20

    wrightk20 New Member

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    Thanks Noah. i was about ready to condemn that gauge and install a different one, but it might be accurate after all. This spring when i get everything shut down i will have to fix or replace the auto fill valve and then reset my pressures. I don't like the thought of having that much pressure on the lines in my basement. I have nothing but pex tubing down there and i would hate to have one pop off a fitting. Maybe it wouldn't be an issue though. idk
  17. maple1

    maple1 Minister of Fire

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    I'm also not comfortable with pressures any higher than necessary. The most my heating system sees is 15psi.

    In the spring or whenever it is that you do some changes, I'd also add another guage or two for redundancy. They're cheap - and do fail on occasion.
  18. wrightk20

    wrightk20 New Member

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    Thats a good idea maple. What would you say is the bare minimum psi at the highest spot in the system should be? Kevin
  19. maple1

    maple1 Minister of Fire

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    Depends mostly on how high above your boiler your water needs to go.

    Not sure I'm the best example to follow, but - my boiler is in my basement, and some of my rads are two stories up. I filled to 10 psi cold at the boiler. With my expansion, it tops out when hot to about 15 psi at the most on my guages. The water makes it up & around my zones just fine. I didn't fully research what I SHOULD be running for psi, but seems to me from some reading that it should be more than I am to get good flow up top. But that's what I'm doing and it's working. Actually, there was a point in my 'break in' operation where my pressure gradually dropped some (I think from air working its way out) - I think I was at around 8 min/12 max - and things still worked good. I added a bit more water to bring it back up, but not sure I needed to.

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