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Weil-Mclain GV-6 lockout

when it is very cold and more than one zone needs heat, boiler goes into lockout with TSTAT & power blinking. - manual states; boiler water does not achieve 130F within 20 minutes. I installed Taco zone control to rule out stray voltage on thermostat cuircuit. I notice that when this happens, water entering the boiler is


  • icesailor
    icesailor Member Posts: 7,265
    Primary/Secondary Piping

    What series # is the GV-6? Series 3 and 4 have two circulators. It sounds like the boiler is piped without a primary loop and the return water never gets hot enough to satisfy a safety feature of the controls.

    If it IS piped "Primary/Secondary", are the two "closely spaced tees". actually closely spaced on the same pipe plane (like both on a horizontal plane) or is one "closely spaced tee" actually being used as an ell going from the horizontal to the vertical with the secondary tee going through the run of the tee and injecting cold return directly back into the boiler. You need to tell us which series GV it is.

    Post photo's of the piping. Someone will spot the problem.