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2 stage gas valve on steam boiler

mike terry
mike terry Member Posts: 33
I just noticed today that this alternating reciever system Ive been working on has a 2 stage valve. shes on high fire all the time and has been for years.When I started the system today,I waited till the steam was up and I had abt 1/2 pound on the gauge,and cut her back to low fire.Of course I had longer run time on the burner but it was able to make it to cut out(1.5 or 2 pounds)So how would I control this Whith another pressuretrol? An outdoor stat? I would say it might pick up the system when its stone cold on low fire Guess it would take longer. but maybe I only need high fire on cold start up or when its really cold outside.any options ?
Mike Terry


  • Steamhead
    Steamhead Member Posts: 16,732
    You can control it with a Vaporstat

    that has a single-pole double-throw switch in it. Get the one that cannot be set higher than 1 PSI, and set it to trip at 8 ounces or so. Honeywell's model# is L608A1046.

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  • mike terry
    mike terry Member Posts: 33
    would I

    have just one vaporstat or would this function along with the presurtrol......there is another control on this boiler but I have assumed that its a high limit safty since it has a manual reset.
  • scrook_2
    scrook_2 Member Posts: 610
    vaporstat and high/low fire steam

    Have the SPDT vaporstat switch the gas valve from high fire to low fire (that's why double throw) at say 8 oz, and back to high fire at say 2 to 4 oz. Note this control sets high/low only.

    The pressuretrol, set as low as you can get it, say 1.5 to 2.0 lbs cut out and 1.0 to 1.5 cut in, would remain, it's function would be to shut off the (now low firing) burner when you got to 1.5 - 2 psi (assuming the thermostat was not yet satisfied). Note this is still controlling fire/no fire.

    The manual reset safety (is this another pressuretrol, or a low water cut off?) would remain as a safety.
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