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Pressuretrol Question

In Holohan's book "We Got Steam Heat" he says that just about any steam system in any house will operate best at a cut-in of .5 psi and a differential of 1 psi.
I have a 1.5 story 2100 sq.ft. Craftsman style house with 12 radiators and steam heat. Here is a pic of my pressuretrol. The cut in is set at 2 psi and the Diff is set at 3.
Why does the round pressure gauge right below the pressuretrol read less than 1 psi?
Is it ok for me to set the cut-in to .5 and the Diff to 1?


  • Jamie Hall
    Jamie Hall Member Posts: 23,271
    Those 0 to 30 psi gauges -- which are required by your insurance and likely by your building inspector -- are usually pretty useless at the low pressures the system operates at. To really know what is happening you need an additional low pressure gauge.

    That said, if your pressuretrol is anything like accurate, your settings are way too high. The cutin should be somewhere just over the 0.5 mark, and the differential set at 1.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 1,003
    If you install a low pressure gauge in addition to the 0-30 gauge, it needs to be kept isolated when not attended. Most low pressure gauges can't handle pressure more than about 130% of full range.

    As @Jamie Hall said, it is required by code.

    Don't just permanently swap them.

    EBEBRATT-Ed Member Posts: 15,510

    because the pressure control scales are inaccurate don't adjust it until you get a low pressure gauge on it.

    The object is to keep the pressure low.

    keep in mind if you are NOT building steam pressure on the gauge your better off that if you are building pressure.

    The lower the pressure you can run without short cycling the burner the better off you are. You don't have to have pressure to heat a house
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    I'd even say keep the pressure low even if you are "short cycling" the boiler. What is the harm? A few extra cycles on the gas valve?
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • Stardance
    Stardance Member Posts: 23
    About that 0 to 30 psi gauge: I've never seen it move. Not when the boiler fires up or any other time. Are they that inaccurate or is it nonfunctional?
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    They are notoriously, ridiculously, universally nonfunctional
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el