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Boiler Pressure Reading Too High

Hello everyone,

So I've been working on a relatives one pipe steam system recently due to an outrageous gas bill.

The first thing I did was insulate the lines as they had removed their old insulation due to it being asbestos.

The second thing I noticed was a high pressure reading on the boilers pressure gauge (8 psi).

So I changed the 2 main air vents assuming they weren't getting enough air out of the system and set their subtractive Honeywell pressuretrol for a cut-in of .5 psi and cut-out of 2 psi.

But the pressuretrol never actually shuts the boiler off. Instead the boiler continues to run and the pressure goes up to 8 psi. The boiler only shuts off once the thermostat is satisfied.

So by this point I'm not really sure what the issue is.

Is there something I'm missing?

What could be causing the high pressure reading?


  • neilc
    neilc Member Posts: 2,258
    you need to (check and )clean the pigtail under the Ptrol, it's clogged.
    also check that the hole it's screwed into is clear, either at the boiler, or into the Low Water Cutoff.
    Post a picture or 2,
    known to beat dead horses
    EBEBRATT-Ed Member Posts: 13,848
    What @neilc said is correct
  • Engineer
    Engineer Member Posts: 2
    edited January 2019
    Thanks so much for the quick responses. I really appreciate it.

    So I removed the siphon and cleaned it. The pressuretrol is still not working correctly.

    I wondered if maybe the pressuretrol was fine and it was simply the pressure gauge that was showing an incorrect reading.

    I noticed the pressure gauge went down to 20in vacuum when I turned the boiler off. After removing it it didn't zero out. I take it the lack of a siphon is what damaged it. For what it's worth when I put it back it slowly went from 20in vacuum to 11 psi.

    Another thing is the water in the gauge glass is constantly fluctuating. When the boiler is off it's about 3/4 full but when it's running it's gets as low an inch from the bottom.

    Also the automatic water feeder seems to be adding about 2 gallons of water every week.

    Thanks again for all the support. I truly appreciate it.
  • JohnNY
    JohnNY Member Posts: 3,206
    That gauge is probably filled with that dirty boiler water.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Plumbing in NYC or in NJ.
    Take his class.
  • Gsmith
    Gsmith Member Posts: 426
    Take off that 0-30 psi gauge, put in its place a nipple and 90 deg elbow up, then pigtail and a T and buy a new 0-30 gauge and a new 0-3 gauge. Then you will be able to see what pressure the boiler is actually operating at. You need the 0-30 gauge for code reasons, but it most likely will not ever show pressure if the system is setup right.