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Pressuretrol Issues

spr1025 Member Posts: 4
Hi all. Wanted to start off by saying thank you to Mr. Holohan and the rest of you experts on here. I've purchased and read the books and frequently come back here to read advice. I learned a ton about steam systems from everyone here.

We bought a house with one pipe steam heat in 2018 and it had all the classic issues. Water hammers from radiator not being pitched, no main vents, no insulation, completely unbalanced system. I started doing what I could, and as of 2 weeks ago I finished adding main vents and most of the insulation and the system was running beautifully. The only issue was later in the cycle (in the morning after we had the temp setback over night) the radiator vents were getting loud. With my new found (misplaced) confidence that I know all about steam heat, I thought it was caused by the pressure building up later in the cycle.

The subtractive Honeywell Pressuretrol (0-5 psi) we have was set at main 2 psi and diff 1.5 psi. I tried to lower it to 1.5 and 1 per Dan's suggestion in the book. After doing that though, the system is acting erratically. Seems like a classic example of if it ain't broke don't fix it, but it's too late for that now. I get water hammers again and it seems like it's running at a higher pressure than it was before. The radiator air vents are whistling much louder and sporadically. I have since changed the Pressuretrol settings back to the original, but the issues are still there. My original thought is that when I changed the pressuretrol, I somehow messed with the cut-in pressure and the differential dial is no longer working. All I did was tighten the screws on top and didn't change anything internally. I noticed the 30 psi gauge on there reads up to 2 psi now (almost immediately in the cycle), and I never really remember that happening before I changed the settings. When it reads 2 psi on the gauge is when the vents are all making noise now and the water hammers start. It doesn't get above 2 psi, so I believe the cutout is working correctly. I don't know the age of the pressuretrol, probably in the 5-10 year range.

Does anyone know if there's a way to troubleshoot this pressuretrol? Does my thought process make any sense or am I way off?

It is possible something else more serious is happening and I should call an expert right away (there's a few in my area on this site)?

If it's a shotty pressuretrol, I would probably replace it with a vaporstat and add in a low pressure gauge.

There's a couple photos attached and I can take more or send more info as needed. Thank you in advance for any help or advice!


  • Jamie Hall
    Jamie Hall Member Posts: 17,165
    That is an excellent pressuretrol Unless it is actually broken somewhere, don't even think about replacing it. In your pictures it is set for a cutout of 2 psi and a differential of 1.5, so if it's cutting out at 2 that's exactly what it should do. That said, however, it looks almost as though it isn't quite level, and that type of pressuretrol is very sensitive to being exactly level. Please check that.

    I will mention several nice things about it --that mercury vial is the switch, so you can see immediately whether or not it is working properly. As the pressure rises, the mercury bulb will tilt to the left until it tips over and the boiler cuts out. Then as the pressure drops to the cutin, it will tilt back and the boiler will fire again. If it's doing that, it's working.

    I'm not sure what you mean by "tightening" the screws on top. They don't tighten -- all that should happen when you turn them is the indicator -- and thus the setting -- should move up or down the respective scale.

    I doubt that the pressure gauge is too accurate -- you could add a low pressure gauge to get a better idea.

    Now. All that said, keep in mind that a pressuretrol does not create pressure. It measures it. And if the pressure is rising to 2 almost immediately, there is something else amiss.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 9,001
    Also, as you look at the pigtail, as it heats and cools it will "twist" as if it is coiling and uncoiling.

    This will rock the ptrol from side to side affecting the movement of the mercury bulb

    The pigtail should be rotated 90 degrees so the movement of the coil will rock the ptrol front to back.

    Inside the ptrol is a pendulum hanging on the right side, should be a white dot painted inside to show you that the control is level.

    A copper pigtail is preferred to avoid plug ups.

    When it is changed, if the 90 ell under it is changed to a Tee with clean out plug then one can assure that the opening into the boiler is also clear.
    Also check the bottom of the ptrol for sludge.

    You could add a brass tee and fittings above the pigtail to add a low pressure gauge.
  • spr1025
    spr1025 Member Posts: 4
    Thank you Jamie and Jughne for the info. It appears to be level (photo attached). Tightening was probably not the right word. All I did was turn the screws on top to adjust the settings. It was after this that the pressure issues started.

    I agree that the cutout seems to be working. The pressuretrol stops the boiler from getting above ~2 psi (like you said hard to tell on the 30 psi guage). I'm just not sure why the start up pressure suddenly jumped up after I played with the pressuretrol settings. It's possible it's unrelated.

    I also just looked for the white dot. The pendulum appears to be pointing at the white dot. I tried taking a picture but I couldn't get a great focus on it. What you are saying about the pigtail also makes sense. Maybe I will get someone to come out to take a look at the setup and make a few changes based on your suggestions (and add a lower pressure guage). But from both of your comments, it seems like the pressuretrol might not be the issue like I thought it was.
    JUGHNE Member Posts: 9,001
    If the pigtail is partially plugged, the ptrol will not "feel" the actual steam pressure inside the boiler.
    As mentioned the entire piping to the pigtail must be open into the boiler.
    That 90 ell under the control can get plugged also.
  • spr1025
    spr1025 Member Posts: 4
    Thanks again Jughne. This has been keeping me up (and waking me up when the heat kicks in). I just looked and it appears that the water level in the guage glass is bouncing pretty severely and even was all the way at the bottom at some point. Are there any other ideas that could be causing this? Since adding the main vents, maybe some gunk got dislodged and the water needs to be flushed and/or skimmed? Something more serious?

    I contacted a pro from this site, but I'm just wondering how urgent this matter is. I can deal with some noise and discomfort for a little while...
  • spr1025
    spr1025 Member Posts: 4
    Quick update on this. SOLVED. As suggested above the pigtail/output of the boiler was clogged up (photo attached). I'm guessing the boiler would ramp up to a higher pressure, causing the pipes and radiators to see that high pressure. But the pressuretrol was not able to sense this because of the blockage. I'm back to quiet and balanced heat again. Thanks!

    Thanks to ASM Mechanical in Staten Island, NY for the quick fix also.
    JUGHNE Member Posts: 9,001
    Thanks for feedback.....we always appreciate it on the wall.
    So many times we never hear back.
  • neilc
    neilc Member Posts: 1,478
    we ought be able to tag threads,
    "Clogged boiler port / pigtail"
    to show folks what to look for,