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Pressuretrol vs. Vaporstat

Gene_2 Member Posts: 59
Our 1922 one pipe low pressure steam system is getting an early Christmas present: A vaporstat to replace the pressuretrol, which is currently cranked down to 1/2 psi cut-in and 1 psi differential.

There are 2 vaporstat models: the L408A1157 has a 0 - 4 psi pressure range, and the L408A1132 has a 0 - 16 ounce/sq.in. range. Which one should I get?

I'm confused by Dan's discussion on page 14 of "The Lost Art of Steam Heating." He says to set a Pressuretrol to 1/2 psi cut in and 1 psi differential, but then he says if you have a Vaporstat, set it "to Cut In at about four ounces and Cut Out at about ten ounces."

But in the preceding discussion, he says the radiators need 1 psig to heat the house. And my piping losses are probably around 2 ounces (longest run is about 85'). So don't I need a cut out of 18 ounces/sq. in.? You can't set the 0 - 16 oz./sq/in. Vaporstat this high.


  • Bob W._3
    Bob W._3 Member Posts: 561

    FWIW this is my thread on the same issue earlier this week:

  • Steamhead (in transit)
    Steamhead (in transit) Member Posts: 6,688
    Get the 1-PSI Vaporstat

    If the house has had any insulation, storm windows, weatherstripping etc. added you don't even need 1 PSI at the rads. Ounces rule!
  • go low

    Hi Santa,

    What a nice present for a steam system. Pick the 0-16 oz. and try to operate around 8 oz., that will be enough to heat the house.

    Things to add to the Christmas list:

    1) Lots of new vents with plenty of capacity. The system will need plenty of venting to keep the burner from cycling on the pressure control.

    2) A professional burner tune-up to peak your efficiency and make sure you are not over-firing. Too much steam can also make the burner cycle on the pressure control.

    3) A thermostat check up to make sure that it is set for your steam system. You want to avoid the t-stat cycling the burner during a call for heat.

    Best regards and happy shopping, Pat
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