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Please help with steam boiler pressuretrol and steam pressure.

Andy_N Member Posts: 8
Hello all,
Thank you in advance for the helps and tips.
We replaced the oil steam boiler in September of 2018 with a gas boiler, it was working fine last year however this year I have run into major issues with the new boiler.
From what I can see the pressuretrol does not turn off/ turn/on the boiler when it hit the max/min pressures limit.
The boiler will turn on when the Tstat call for heat and run for about 5 minutes and then off 3 minutes and on/off again until temperature reach what the Tstat set or until pressure in the boiler reach to a point that is open the relief valve.
The pressure usually does not get that high unless I set the temperature on the Tstat to 72 or above.
When the temperature set to 68 the boiler usually shut off at around 5psi according to the 30 psi gauge that the boiler came with.
After reading through many discussions on this forum and others, I believe this could cause by a clogged pigtail or a bad pressuretrol.
It seem like I need to take off everything around the pressuretrol before I can take the pigtail and the pressuretrol out of the boiler.
I have attached a picture of the boiler setup and looking for helps to see what the best thing to do since we in the middle of winter and don't want the house not to have heat for too long.
Thank you for all your helps in advance.


  • Jamie Hall
    Jamie Hall Member Posts: 21,110
    Is that photo with the boiler off? If so, notice the pressure gauge -- it's reading around 2 psi. Those 0 to T30 psi gauges -- which are required by your insurance and most codes -- are none too accurate.

    That said, if your boiler keeps on firing until the pressure relief valve operates, you have indeed a problem with the pressuretrol. The most likely -- and common -- problem is that the pigtail is gunked up (and probably the opening into the boiler as well). The solution is, as you note, to take the pressuretrol and pigtail off and make sure that everything is clear. Nobody did you any favours with that installation, however, and I'm not sure but what you are right -- you may have to take the pressure gauge and low water cutoff off the boiler to get enough room to swing the pressuretrol and pigtail around and off, unless there is enough room in back of the pressuretrol to unthread it from the pigtail.

    There is a way to take pressuretrols apart. It's not for the faint of heart, as it's all too easy to have real trouble getting it back together right, so I can't really recommend it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Andy_N
    Andy_N Member Posts: 8
    @Jamie Hall That picture was taken after the boiler finished it first cycle, the pressure gauge is usually at 2.5 psi when the boiler shutoff.
    The boiler stay off for about 3 minutes and the pressure goes down to around 1.5 and it turn back on again and it run for around another 5 minutes at this time the pressure gauge is at 5 psi, this is usually when my Tstat tell it to shut off since the temperature is reach if I set the temperature to 68, and if the Tstat set for anything higher the pressure continue to build up.
    As for taking off pressuretrol there is only about 1/2 inch gap behind it so there is not enough opening to taking it off.
    I have measured the diameter of the pressuretrol and the pigtail it seem that I will also need to take off the valves for the water glass to get it out.
    At this point I want to be sure is the pressuretrol/pigtail before I take everything off.
    My concern is that my boiler turn off for 3 minutes after every 5 minutes of run time even though the pressuretrol is not working, is this how the boiler supposed to work?
  • KC_Jones
    KC_Jones Member Posts: 5,409
    Why do you think it isn't working? If the boiler runs, builds pressure, then cuts off and back on after a reduction in pressure, that sounds like a functioning pressutrol to me. Also keep in mind those devices are known to be wildly off. If it isn't working, then what else is cutting the boiler off?

    Now if you want to discuss the operation in the context of why it builds pressure so fast and does all the on and off, that is quite a different discussion.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Andy_N
    Andy_N Member Posts: 8
    @KC_Jones at this point I am only guessing since the cuts off is at different pressure everytime.
    First cuts off is at 2.5 psi 2nd cuts off is at 5 psi and 3rd cut off is around 7 psi.
    As for how accurate is the internal syphon gauge that is attached to the boiler? that I don't know, however I have witness the relieve valve open when that gauge hit 14.5 psi.
  • KC_Jones
    KC_Jones Member Posts: 5,409
    The pressurtrols are know to be wildly off. If your relief valve is popping then, yes I agree you have something going on here.

    As an aside, if you are able to pop the relief valve I would suggest you have other issues, not enough venting, or more likely a wildly over sized boiler. A safety relief valve is a necessary part of the system as a final line of defense, but with a properly sized boiler and proper set up you shouldn't be able to blow that valve. If you do I would speculate it should take hours of run time, which it doesn't sound like you are getting.

    Welcome to the rabbit hole, I hope you are ready for the steam ride.

    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Andy_N
    Andy_N Member Posts: 8
    I definitely have an over sized boiler.
    Crown boiler BSI172ENPZZPSU
    Rating input 172.000 BTU/hr
    Output 142.00 BTU/hr
    I have total of 8 radiators so even without calculating the EDR for the radiators I know the boiler definitely over sized from reading the information in the forum last few months.
    Since there is nothing I can do with over sized boiler at this time I thought If I can get my pressuretrol working with the cut in at .5 and cut out at 2.0 psi that would help with the pressure going from that high? This is probably out of my league however the more I read into steam heating the more interest I get so definitely going to try to get this thing to work out.
  • KC_Jones
    KC_Jones Member Posts: 5,409
    It will help with the pressure going too high, but keep in mind it will exacerbate the cycling problem as it will be cutting in and out at a lower pressure.

    Sizing a steam boiler is not hard, boggles my mind that the contractors won't do it.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • Gsmith
    Gsmith Member Posts: 423
    Probably the easiest, but not cheapest way to take of and clean the pigtail is to but a new one, get brass, and a few same size unions and nipples. Cut the existing pigtail apart and remove the pieces. Turn the boiler off first. And while you’re at it install a tee and a low pressure gage above the pigtail, basically in parallel with the pressuretrol so you can accurately read the pressure it builds to. I’d suggest a 0-5 psi gage with a valve to turn the gage off when not in use or until you get the system pressure to be consistently under 5 psi. Out some water in the
    New pigtail before you put the pressuretrol back.
  • Andy_N
    Andy_N Member Posts: 8
    @Gary Smith Thank you for the suggestion, that sound much easier than taking everything around the pressuretrol out.
    @KC_Jones Thank you for the heads up with boiler short cycle.
    I have thought about it since there are many posts regarding over sized boiler and short cycle on this forum, however that is probably way better then what I am dealing with now. At the very least I don't need to worry about the boiler blowing up from high pressure.
  • Gordo
    Gordo Member Posts: 839
    You might be able to remove the two screws that hold the diaphragm onto the control body, and remove the diaphragm from the pigtail, then take off the pigtail.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • Andy_N
    Andy_N Member Posts: 8
    edited January 2020
    Thank you all for help with the pressuretrol issue.
    I was able to remove the pressuretrol without taking everything around it off the boiler.
    As expected the pigtail was clogged so the pressuretrol was not function correctly.
    After clean the pressuretrol and put in new pigtail and additional 15psi gauge my boiler is now running at 3psi max.
    I have attached the picture of clogged pigtail and my new setup.
    Thanks again for all the help.

    EBEBRATT-Ed Member Posts: 13,440

    Looking at your first picture the water level looks like it's below the mark on the gage glass not sure if it is or not. You could be cycling on the low water cutoff as well

    Also, for the pigtail to plug up in a 1 1/2 years how much and how often do you have to add water?

    After looking at the pigtail I would be concerned with the boilers longevity.
  • Andy_N
    Andy_N Member Posts: 8
    That picture was taken when the water level was already below the half mark, and the boiler was running at the time so the water level drop a bit.
    I have the automatic water feeder set to 3 gallons before and just adjusted to 2 gallons when I installed the new pigtail.
    The feeder seem to add only what I drained out, usually that is around 3 gallons a month.
    I believe part of the reason why the pigtails got clogged is because the automatic water feeder was feeding too much water into the boiler, 3 gallons seem to fill the gauge glass to almost full and pushing a lot of water into the pigtail when the boiler run.
    The old pigtail was setup horizontal to the waterline so that might be another reason the pigtail getting clog fast.
    That was just my guessing.