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Weil CGt diverter

kcopp Member Posts: 4,386
I service 2 Weil Mclain CGt boilers.
Both are having issues w/ the heat staying on even if the Thermostats are not calling for heat. I even pulled the wires off the boiler and they would still circulate water.
Sometimes cycling the power gets the issue to reset.
Would a diverter valve sticking cause this to happen? I cant believe this is electrical...especially w/ two boilers.


  • hot_rod
    hot_rod Member Posts: 21,815
    Do they have zone valves connected? What wires did you pull off? Is there an outdoor reset control connected?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • kcopp
    kcopp Member Posts: 4,386
    edited November 2023
    1 zone.
    Pulled the tt off the boiler / end switch .
    Simple cast iron block w a coil inside.
    Side wall vent in stainless.
    No outdoor sensor.
  • kcopp
    kcopp Member Posts: 4,386
    So the issue turns out is a sticking diverter valve.
    Its not electrical in any way....
    The piston inside the 3 way valve has very tight tolerances. There is sone Non-Barrier tubing in the system.
    Strange thing is that is sticks every so often and when it does it stays in heat mode.
    Very odd...
    I have done a power flush, replaced the piston and added an inhibitor.
    fingers crossed.

  • ScottSecor
    ScottSecor Member Posts: 839
    We service two of them as well, one we installed.   Not our favorite boiler or three way valve.