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Utilizing circulator hold off with hydrolevel 3250 and taco zone valve control

I would like to utilize the circulator hold off function of the hydrostat 3250. I will be using 1 circulator with zone valves and ataco zone valve control. Originally I planned to just run the circ off the hydrostat but realized if a zone valve fails to open, the pump will be running dead headed. I see that the pump end switch on the taco zone valve control is just a set of dry contacts. So now I plan to run the hot leg of the circulator wires from the hydrostat and pass through the pump end switch of the taco zone control. This will ensure that the zone end switch in the taco controller will have to be closed in order for the hydrostat circulator power to turn the pump on. Anybody see any issues doing it that way?  


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    If the zone valve fails to open, technically (almost always) the end switch won't close, and T-T won't make
  • Dave H_2
    Dave H_2 Member Posts: 553
    And as Steve said above, the circ will also not turn on.

    On a ZVC controller, the sequence of operation is:
    1. Thermostat Call
    2. Power to zone valve
    3. End switch on zone valve closes
    4. XX (isolated end switch) closes and XX (pump end switch) closes

    Take out the end switch on the zone valve and the boiler nor the circ turns on.

    Dave H.
    Dave H
  • super_snop
    super_snop Member Posts: 48
    Thanks guys. I was under the impression that if there was a call for heat from thermostat XX would close and the end switch for the pump would only close after the zone valve end switch makes. Looks like I can wire the circ through the hydrolevel and still be able to utilize hold off function without worrying about pumping with a closed zone valve. 
    Dave H_2