Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Oversized Boiler? Or inappropriate location for pressuretrol?

In the basement of the rectory of my parish church sits a gigantic WeilMcClain Natural gas steam boiler that, although I did not yet do the calculations, seems waaaaay over-sized for the building it heats.

Whats happening is it's short cycling like a yo-yo and I can hear the pressuretrol causing it as it's click is audible.

Since changing the boiler is not an option the parish priest wants  to entertain at this time anyway, I am wondering if their is anything that can be done to tame this beast a bit?

Their is one six inch riser coming out of the boiler connected to the steam main. The pressuretrols(their are two)are connected to a manifold on the opposite side of the boiler about as far from the supply main steam tapping as they can get. Can this cause a rapid rise and fall of pressure where the pressuretrols are located giving them a "false" reading? And how much can the flame be adjusted down on this boiler without causing a hazardous situation?


  • MDNLansing
    MDNLansing Member Posts: 297

    As long as the pressuretrol is reading the pressure in the steam chest or header, it shouldn't matter where it is located. Could you take some pictures of the installation please?

    Also, what are the high and low pressures set to right now? When the cut out is reached, how long does it take before the boiler fires back up? If so, what pressures are being registered when the pressuretrol cuts out and back in?
  • Jamie Hall
    Jamie Hall Member Posts: 22,934
    Couple of things you could try

    with absolutely no guarantee that either one will work...

    First, is there a way you can put one of the pressuretrols on the steam main itself?  Or even (not as good) on the riser?  That way it will be reading the real pressure in the system, which may not fluctuate quite so much.  That one should be the controlling one -- set to perhaps 2 psi max.  The other one should be the backup set to perhaps around 5 psi or so.

    Then you can also put a pressure snubber on the pigtail to the controlling pressuretrol (make sure it's steam rated).  That can sometimes work wonders.

    Of course, if the boiler is really seriously oversized, there isn't much of anything that will help!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • john walsh_2
    john walsh_2 Member Posts: 64

    The pressuretrol settings are 2psi cutout and .5 cutin. I will try to get some pics of the beast in the near future. It was installed in 08 and seems monstorous for the application.
  • john walsh_2
    john walsh_2 Member Posts: 64
    No time at all

    once it reaches it's first cutout on pressure, it drops to it's callin set point  within 30 seconds or less then runs for about 45 seconds to a minute and then goes off on the high pressure limit setting. Only to repeat the cycle again and again.
This discussion has been closed.