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Boiler pressure acting strangely

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meghanp10
meghanp10 Member Posts: 12
Apologies for the long post.
This morning, boiler pressure had randomly dropped to 2 PSI after sitting around 14 PSI for days. I added water until it was at 12 PSI. Now this evening, around 9 pm, heat was on and the pressure was way up at 35 PSI and the relief valve had not blown! I drained a bunch of water until the pressure was back down to 14 PSI and within 20 minutes it had gone back up to 18 PSI. Could a full expansion tank be causing this? I don't think water is being added to the system since I keep finding it with a very low pressure and have to manually add water.
I'm afraid to leave the heat on tonight but it's -25°C so I don't really want to turn the heat off either..
Obviously, next step is to call a professional, but I'm curious if anyone has any idea as to what's going on.
Thanks in advance!

Comments

  • mattmia2
    mattmia2 Member Posts: 9,734
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    does it have a bladder type or conventional expansion tank?
  • HVACNUT
    HVACNUT Member Posts: 5,856
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    The gauge might not be correct.
    If you have a diaphragm expansion tank, does the air eliminator work?
    Set the pressure to 12 psi cold.
    Shut off the manual valve to the PRV (auto feeder), and keep an eye on it and let us know.
    A few pounds plus or minus with cycling isn't a concern.
  • meghanp10
    meghanp10 Member Posts: 12
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    > @mattmia2 said:
    > does it have a bladder type or conventional expansion tank?

    Conventional.
    Also, an update. I powered the heat off completely last night due to fear and it was at 14 PSI when I went to bed. Now it's at 30 PSI...again.
  • Zman
    Zman Member Posts: 7,572
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    If it is gaining pressure with the boiler off, have an issue with either the fill valve or a tankless coil/indirect water heater.

    Do you trust the gauge? One of these is an easy way to verify a well as document the peak. https://www.supplyhouse.com/Watts-0069770-IWTG-2-1-2-Hose-Connection-Gauge-0-200-psi?gclid=CjwKCAiAuqHwBRAQEiwAD-zr3b7t6RHA7UM5oFgUzW8EhfkzeR_uAd3paXhkxQhR-HtcvHzWIP8gThoCFt8QAvD_BwE

    Are you able to isolate the domestic water?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    STEVEusaPA
  • meghanp10
    meghanp10 Member Posts: 12
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    > @Zman said:
    > If it is gaining pressure with the boiler off, have an issue with either the fill valve or a tankless coil/indirect water heater.
    >
    > Do you trust the gauge? One of these is an easy way to verify a well as document the peak. https://www.supplyhouse.com/Watts-0069770-IWTG-2-1-2-Hose-Connection-Gauge-0-200-psi?gclid=CjwKCAiAuqHwBRAQEiwAD-zr3b7t6RHA7UM5oFgUzW8EhfkzeR_uAd3paXhkxQhR-HtcvHzWIP8gThoCFt8QAvD_BwE
    >
    > Are you able to isolate the domestic water?

    I honestly know next to nothing when it comes to this system. The pressure gauge reacts seemingly correct when I have had to add water so I assume it's working.
    It will also randomly drop severely in pressure too and then no water gets added so surely it can't be a leak into the system?
  • meghanp10
    meghanp10 Member Posts: 12
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    I should also mention it's a very old boiler. Around 100 years old. So it's not surprising that there are issues.
  • meghanp10
    meghanp10 Member Posts: 12
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    I also just drained water until it was at 12 PSI, turned the heat back on and now the pressure is up to 14 PSI, which I'm assuming is what should happen?
  • HVACNUT
    HVACNUT Member Posts: 5,856
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    So according to the gauge we've gone from 2 psi to 35 psi without the relief valve blowing or lack of heat or banging pipes or anything of that nature?
    Other than the pressure reading, does everything else seem ok?
    Is the relief valve and gauge also 100 years old?
    Get it checked out but it could be a faulty gauge.
    Pics? I want to see a 100 year old boiler. Dont keep it to yourself.
  • meghanp10
    meghanp10 Member Posts: 12
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    Pretty much, yes.
    My plumber just got back to me and said it's likely the expansion tank is full so the extra pressure has nowhere to go.

    Picture of my 100 year old boiler is attached. Haha
  • mikeg2015
    mikeg2015 Member Posts: 1,194
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    It likely has a Compression tank located up at the ceiling, not a modern , expansion tank.

    FYI a “plumber” should not be working on that boiler. It needs a HVAC company that knows how to set up a power burner using a combustion analyzer.

    You really, really really should consider replacing that boiler. It likely lacks most of the modern safety devices, and efficiency is probably around 70% at best, if that. I see a damp floor around it, you sure it’s not leaking?
    STEVEusaPA
  • jerryb46
    jerryb46 Member Posts: 59
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    you are not draining the expansion tank right,to do it you need a 5 gal bucket and a 5 ft washing machine hose,Attach hose to tank drain shut off valve to tank coming from boiler,open drain in bucket.will get approx 5 -7 gal of water then its stops now take hose and blow in it you will hear sound of gurgle in tank blow until you can't anymore and pull hose out of your mouth into bucket,move it fast you don't want the black water in your mouth,keep doing this until you get the amount of water the tank holds,the final amount of water will be real sludge close drain open feed to tank let pressure equalize,(may take some time). pressure gauge will should stay steady at set psi,Good Luck
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited December 2019
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    mikeg2015 said:

    ...efficiency is probably around 70% at best, if that...

    I'd estimate 40%-50% overall system efficiency.

    There was an error rendering this rich post.

    Solid_Fuel_Manmattmia2Zman
  • Steamhead
    Steamhead Member Posts: 16,885
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    mikeg2015 said:

    You really, really really should consider replacing that boiler. It likely lacks most of the modern safety devices, and efficiency is probably around 70% at best, if that. I see a damp floor around it, you sure it’s not leaking?

    More like 40% efficient, according to one of my Dead Men's Books. That's what we call a "snowman" since it would have been covered with asbestos insulation when it was first installed. This type of boiler was relatively cheap to buy, but it lets a lot of heat go up the chimney.

    There is a fair chance you could cut your gas consumption in half when you have it replaced.

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • meghanp10
    meghanp10 Member Posts: 12
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    @mikeg2015 yes, tank strapped to the ceiling. I have attached a pic. My plumber is HVAC as well. Very small town. Don't have the luxury of a bigger company.
    There is some leakage that's been happening for many years according the accompanying rust stains.

    @jerryb46 there is only one valve I can open on the tank (see pic). I barely got any water out when I tried draining it.
  • Steamhead
    Steamhead Member Posts: 16,885
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    That's the only drain on the tank? If so it's in the wrong place.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • meghanp10
    meghanp10 Member Posts: 12
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    @Steamhead yeah, I thought it was strange. When I fired everything back up, I did hear water go into the tank and then pressure dropped by 2 PSI.
  • Steamhead
    Steamhead Member Posts: 16,885
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    Oh boy. Well, you need someone who knows this stuff. From the label on the boiler, and the fact that your original post mentioned degrees Centigrade/Celsius, I'm guessing you're in the Great White North somewhere?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • jerryb46
    jerryb46 Member Posts: 59
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    sent a text about ho to drain ,Steamhead hit the target about the drain in wrong spot (i didn't see picture that is now shows ).Dis regard my lost post
  • meghanp10
    meghanp10 Member Posts: 12
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    @Steamhead yes, central Saskacthewan.
  • Steamhead
    Steamhead Member Posts: 16,885
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    Unfortunately, our Find a Contractor feature doesn't cover Canada. Hopefully someone will chime in.

    BTW, ISTR reading a story in grade school called "Owls in the Family" which was set in Saskatoon.............
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    That is likely a converted gravity system. Originally had some type of vented tank upstairs (usually in or above a closet in my experience) riveted steel tank maybe. It the 40s or 50s they added a circulator (red pump behind the boiler) and that green compression tank with the soft copper line. I'm guessing you have some nice big cast iron radiators in the house.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • meghanp10
    meghanp10 Member Posts: 12
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    @Solid_Fuel_Man yes, steel rads in every room. It works great...when it decides to work. Haha
    I just can't figure out this fluctuating pressure situation. It seems to work just fine for a week or two and then it all goes screwy again.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    It sure looks like that snowman is leaking
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • mattmia2
    mattmia2 Member Posts: 9,734
    edited December 2019
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    It looks like someone that knew what they were doing did a fair bit of work on it relatively recently.

    Does that system even have a relief valve? i don't see one, but we're not seeing much of the near boiler piping. Originally with the open tank at the top of the system it wouldn't have needed one, but when the closed expansion tank was added it should have gotten a relief valve.
  • meghanp10
    meghanp10 Member Posts: 12
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    @mattmia2 yes, it has a relief valve. Just not visible in the pic.
    I've lifted the lever on top of it and it spits water out so I don't know why it didn't release water when the pressure went up to 35 yesterday.
    I really have no idea what's going on.
  • mattmia2
    mattmia2 Member Posts: 9,734
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    What pressure is the valve rated for?
  • meghanp10
    meghanp10 Member Posts: 12
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    @mattmia2 it says 30 on the little tag.