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No cut-out control?

juanez Member Posts: 9
Hi, been lurking on the forum for a bit.
This steam stuff is pretty much new to me, and I was trying to understand the system better, and mitigate some of the clanging pipes.

Long story short, there was a leak in a radiator, system was losing water and that in turn seem to have created *alot* of water hammer in the pipes (not sure why though, but, refilling the boiler, fixing the leak has made the sounds *almost* go away).

Anyway, reading on this forum and elsewhere, I got curious to see if I can tweak the settings on my system. From what I could gather, it's set to cut-in at 2psi, which according to what i read here is way too high of a setting for this house... So i dialled it down to 0.5psi and also dialled down the pressuretrol to 2psi.. Well.. That triggered the pressuretrol and it's a manual reset, so i found myself having a burner that did not restart.

Reset it all back to 2 and 10, and reset the pressuretrol.. things are working.

Now to my question... what do i do with this system? I have a cut-in control, but it seems i dont have a cut-out that i can set? (except the manual reset backup pressuretrol)

I couldnt quite find any other posts where there's no cut-out or "diff" settings..

(it's a burnham boiler)

any help much appreciated!


  • Jamie Hall
    Jamie Hall Member Posts: 23,313
    The grey box and the box with the clear cover are both pressuretrols -- just different models. The one on the left, with the clear cover, is a manual reset one -- as you have discovered. It's sort of a backup player. The one on the right is automatic. The single scale which you can see is the cutin pressure -- the pressure at which the boiler will restart -- as you have also discovered. What is a good deal less obvious is that insdide the box is a dial labelled "differential" -- at least I think it's labelled. Might not be. It's white. When you add the differential seeting inside to the cutin outside, you get the cutout pressure.

    So there is a cutot control -- it's just not obvious.

    Most of us recommend dialing that cutin control on the grey box around 0.7 psi for most steam systems, and leaving the differential wheel inside set to 1, giving a cutout of 1.7 psi or so.

    You should take the cover off the grey box, though, and check that the differential wheel is set to 1 -- yours may be set higher.

    If the water hammer comes back, try to locate it (that's hard!) and look to see if there are any pipes which aren't sloped correctly.

    And -- if you don't have it, pick up the little book "We Got Steam Heat", available here and on Amazon -- has a lot of good information.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • juanez
    juanez Member Posts: 9
    edited January 2022
    Spot on! Thank you @Jamie Hall

    I peaked inside yesterday (but, as I'm clueless had no idea what I was looking at) because as I tried to set the cut-in to 0.5 the darn thing actually got fully screwed out!

    Anyhow, this now starts to make a whole lot more sense to me.

    It would seem that the "diff" is set to almost 5!
    And this correlates to what I saw on the pressure gauge while it was operating, it got up to about 6 and the cut off...

    Many many thanks!

    edit: typos
  • juanez
    juanez Member Posts: 9
    actually, I assumed too much. It's unclear (to me) what the diff is actually set to! =)

  • juanez
    juanez Member Posts: 9
    alright, so this was helpful:


    seems like my diff is set to "1".

    and the high psi before maybe can be attributed to poor accuracy on either the gauge or the pressuretrol or something...

    EBEBRATT-Ed Member Posts: 15,532
    on the pa404a control with the grey cover if you loosen the screw on top too much the screw will"unscrew" and the control wont work. take the cover off and look down inside and turn the screw back in to the minimum setting
  • juanez
    juanez Member Posts: 9
    thanks @EBEBRATT-Ed , that's exactly what happened yesterday, luckily it was an easy fix - though, I did freak out for a minute there :)

  • bburd
    bburd Member Posts: 917
    Sometimes the connection between the pressuretrol and the boiler can clog up and prevent the pressuretrol from sensing what is happening in the system. The pigtail and connecting fittings can be unscrewed and cleaned out. It’s also important to make sure the openings into the boiler and the pressuretrol are clear.