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three pressuretrol on the boiler

akira Member Posts: 1
Hi there

Here is a EU plumber who is truly fall in love with steam systems I learned a lot here too and of course every day (we don't have steam in Europe) anyway here is my question: recently I am working on a two pipe system and there are three pressuretrol on this boiler they all subtructive type honeywell Main on the right Diff on the left the very left one has no diff part the very right has rusted water all over it and a setting of 1 main 2 diff. I am pretty new to this but I figured this setting can not be right ( it says on the front SUBTRUCTIVE) I can not take 2 away from 1 right? So what would be the right ideal setting assuming everything else is running ideal. Thank you very very much. I would love to do it by the book. Have a great week.



  • Jamie Hall
    Jamie Hall Member Posts: 23,675
    Three of them?

    that's called overkill on this side of the pond...

    I'm sure one of the more knowledgeable will chime in (I hope) but -- I tend to set Pressuretrols 'by eye'; that is, I set the cutout (main) as low as seems reasonable (no more than two) and then set the differential so that the burner just barely restarts as the pressure drops on a cycle. Pressuretrols at low pressures being somewhat different, one to the next.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • tim smith
    tim smith Member Posts: 2,774
    My guess is that one if for lo hi operation, one is operating

    limit and one is safety manual reset limit. That is how we wire lo hi lo burners for steam boilers.
  • RonWHC
    RonWHC Member Posts: 232
    Commercial steamers

    are normally shipped w/ 2 pressure controls. Some installers, for some reason, install both + the required manual reset. That's the one w/ only 1 scale.

    Some steam heat controls use a reverse, or a straight acting pressure control (or vaporstat), to start the heating cycle timing sequence.

    Follow the wires.
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