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Circulator Zone Not Engaging the Boiler

I am trying to help a friend diagnose his heating system. It is a three zone, circulator system with a Taco Control. One zone wasn't getting the cast iron radiators warm. Initial thought was to bleed the radiators (which resulted in a lost radiator pin and water shooting over the livingroom floor). Fixed that, got pressure back up in the boiler but still no warming. Time to look at the controls. The 24V thermostat that controlled the zone was removed and the wires crossed and the pump started, the boiler engaged and the radiators began to get warm. A trip to the trusty big box, a new thermostat was obtained, and the R and W wires connected to the appropriate positions. Turned up the set point and .... nothing the boiler didn't fire and the circulators didn't apparently operate. (Although I am not 100% sure on the last point since this was a phone diagnosis). Two bad thermostats? Thoughts to try next?


  • If the zone started heating when you crossed the wires at the thermostat, the Taco pump controller is working fine. Check to make sure the wires are properly connected at the thermostat.
    Often wrong, never in doubt.
  • KevinWyman
    KevinWyman Member Posts: 27
    Checked and re-checked with the new thermostat. That's why I am scratching my head. I suggested getting a known good thermostat and swapping out to test (maybe a bad thermostat from the store? Not likely but could happen). But short of that???
  • Ironman
    Ironman Member Posts: 6,868
    Just simply jump "R and W" again. If the boiler fires, the stat is the problem.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Jamie Hall
    Jamie Hall Member Posts: 18,903
    And if it doesn't fire, try crossing the same two wires at the other end -- at the control. If things work then, you have a wiring problem. Wouldn't be the first time.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • You should hear a "click" when you turn up the thermostat if it's a digital model. Also, make sure the thermostat is set to "Heat".
    Often wrong, never in doubt.