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Wiring Taco ZVC404 Zone Valve Control

carlg Member Posts: 12
In my previous question on this forum some of the members convinced me to get a new Taco Zone Valve control (ZVC404)
It seems pretty easy to install and wire.

I just have 1 questions. Do I really need to connect the pump to this new controller? There is 1 pump and it is already wired to the aquastat and the auquastat is already turning it on and off as needed.

I was just thinking wire the t-stats and the zones valves into the control and then connect the 2 wires to the aquastat and then be done.

Or do I really need to rewire the pump??


  • mgdesrochers
    mgdesrochers Member Posts: 20
    There isn't really a need to rewire the circ. if it is working off of the aquastat. You are right about the wiring, go from the end switch on the ZVC to TT on the aquastat and you should be all set.
  • Dave H_2
    Dave H_2 Member Posts: 556
    The idea of wiring the circulator to the ZVC controller is to ensure that the circ doesn't run before a zone valve is open. It depends upon how fast the zone valve opens. The ZVC take the signal for a call from heat from the thermostat, power is then applied to the zone valve. Then once the zone valve is open, the end switch closes and send the signal back to the ZVC. At that point, then the switch for the circ is closed.
    If that sequence doesn't happen, as in stat call for heat, pump and zone valve get power simultaneously, then the circ is dead heading.
    If you are using the XX terminals on the ZVC to aquastat, then you should be fine, leave the wiring alone to the circ.

    Dave H.
    Dave H
    HVACNUT Member Posts: 5,860
    If you don't relocate the circ to the zone board, like @Dave H said, you'll dead head, meaning the circ will run before the zone valve opens, assuming boiler temp is above low limit. That's not good for the pump or the system.
    Shouldn't be too much trouble to run to Lowe's or something and get some 14/2 B/X and a couple of connectors.
    You can go "old timer" and use a hack saw to cut the sheathing. Cut at a severe angle. When I was a kid, the electricians used to say Roto-splits were for pu**ies.
  • kevinbrandon
    kevinbrandon Member Posts: 5
    Forgive me for bringing this beast back to life. I have the same setup as the original poster. I plan on wiring my ZVC directly to my aquastat. The circ pump is wired directly to the aquastat as well.

    My understanding, and feedback from Taco directly, is that the signal will only be sent from ZVC to TT on the aquastat if the end switch is met and zone valve is confirmed to be open. If that is the case, the worry of the pump running with the valve closed couldn’t happen.

    Please share some further insight and stories of problems of this setup though. The last thing I want to do is replace any more parts on our system and spend more money.

    Any help is incredibly appreciated.
  • hot_rod
    hot_rod Member Posts: 22,251
    The switch for the heat call is a dry contact in the relay box, so you can wire most anything thru it within the relays rating.

    Usually a TT connection 24V on the boiler goes to the relay. This starts the boiler on cycle, and usually a boiler pump on or within the boiler.

    Most relay boxes could also run the boiler pump, or buffer tank pump, etc.

    Some relay boxes have additional pump relays for primary secondary, or customizing control logic.

    Correct, any end switch needs to be closed to start the process.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream