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Customer calls says the heat won't stop with the thermostat OFF and wires disconnected. Checked the pressuretrol and was at Cut in .05 lowest.

The pressuretrol must be the problem. What type of pressuretrol is needed and what setting? Anybody

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  • Dave in QCA
    Dave in QCA Member Posts: 1,766
    edited August 2010
    pressuretrol is a high limit only

    A pressuretrol should be set up as a high limit device only, except in some large instututional settings where steam pressure is maintained at all times.  Normally, the call for heat starts the boiler by closing a set of contacts in the thermostat.  The pressuretrol is wired in series with the thermostat and the other safety cutout devises, so the only time it has any effect is if the boiler has run long enough that pressure has built up to the cut out setting.  At that point, the pressuretrol contacts open, and the boiler stops firing until the pressure drops.   A faulty pressuretrol should not cause the boiler to fire continuously, if it is wired properly.

    It sounds to me like their may be another reason for the problem.  Does this boiler supply domestic hot water?  If so, there is another device.  Usually it is a well mounted thermostat on the boiler that maintains the boiler temperature at a given set point, usually around 180 F.  If this is set too high, or if it has failed, or if the conductive grease in the well has dried up, etc., it may be letting the boiler get hot enough to steam before it shuts the boiler down.

    Hope this helps and that you solve the problem.  I would like to know how this turns out.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
  • JStar
    JStar Member Posts: 2,752
    Sounds like.

    A shorted thermostat wire.
  • Tim McElwain
    Tim McElwain Member Posts: 4,487
    Bill is this gas or oil?

    If it is gas disconnect the wires to the gas valve if it shuts off then you know the valve is okay, if not the valve is passing and needs replaced.

    If it is gas is it a powerpile systems? If so disconnect each control if it shuts off then that control is shorted or set incorrectly.

    Keep in mind the pressuretrol and low water cutoff are normally closed and open in the case of  the pressuretrol on a rise in pressure and the low water cutoff on low water.

    Has any work been done in the house if so watch out for pinched(shorted) wires.
This discussion has been closed.