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P-trol margin of error?

About a month ago I cleaned my pigtail and put a 0-3 gauge on the boiler (one pipe steam, IN5).

I never took the time to sit through multiple cycles to see the p-trol actually cut out on pressure until today.

P-trol is subtractive, with main set just under 2. Didn't cut out until gauge read approximately 2.7

Wondering if anything here is faulty or if this is within an acceptable margin of error for the gauge and/or p-trol.


  • Johnson_Rod
    Johnson_Rod Member Posts: 31
    edited February 2017
    Pic of setup
  • WayneMech
    WayneMech Member Posts: 53
    I don't trust the indicator on a control switch. It just gets me in the ballpark. It pays to spend the little extra time, and get it on the money. If possible, I will bend the tab, after setting the pressure, to match.
  • Fred
    Fred Member Posts: 8,542
    If you look at the face of the scale on the Main and Differential, you will see that they have the ability to slide up or down a bit to align the scale to actual tab setting. I would not bend the tab as that may make it read correctly but the pressure is still going to be 2.7 PSI. Slide the scale so that the tab is at about 2.7 and then turn the screw on top to turn the tab down to 2 PSI.