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Taco sentry valve wiring with c wire

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have a Lennox wall mounted boiler (gwm 075ie), I am trying to connect a "c" wire so I can install wifi thermostats. I have 3 zones, currently running 2 wires (r&w). There is an extra wire behind each thermostat, that runs down close to the boiler, none of those wires are connected to anything. My current transformer is rated at 40va.

Unsure of the best way to do this. I have taco valves (z075c2-1) each valve has a "c" connector. Could I just run a wire to each of those connectors to the thermostat? Is the transformer able to handle 3 zones and 3 smart thermostats? Taco says a 40va transformer can run 12 valves

The first image is how it currently is, and I know its wired backwards...





I am wondering if this is the correct way to wire it up? I have seen another post that makes me think perhaps I have the c and the w/y wires crossed. Thanks for your help



Comments

  • pedmec
    pedmec Member Posts: 987
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    absolutely incorrectly wired on the first pic. you will smoke that transformer when the thermostat calls for heat. The second one will work but you don't have to take c-wire from the thermostat all the way to the c-terminal on the zone valve. you can grab the c-terminal on the transformer if it's easier. work smarter, not harder.
  • Joe Mattiello
    Joe Mattiello Member Posts: 707
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    I was looking at your schematic, and don't want to miss inform you. can you contact taco tech support for proper wiring, so we don't compromise anything. Taco tech support 401-942-8000, and ask for tech support.
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,042
    edited October 2023
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    With any zone valve system that is not connected to a zone control like the Taco ZVC 40X I like to follow a simple rule. R from the transformer goes to R on the thermostat. W from the thermostat goes to the motor on the zone valve. In the case of 3 wire zone valves the thermostat W goes to the motor that is not a common wire with the end switch (like the #1 terminal on the Taco 570 series valves). The other motor wire then gets connected to the C on the transformer.
    When you wire it that way, you can easily connect the C from the transformer to the C on the thermostat if needed in the future.

    Looking at the factory diagram and the one that you drew, all the conductors are going to the same place. So your second drawing looks like it will work.
    But to be safe you should consider a

    Smoke Keeper

    (never patented) These keep the factory installed smoke inside the transformer

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Alan (California Radiant) Forbes
  • fixerguy
    fixerguy Member Posts: 3
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    Great. Thank you for all the responses. Very helpful.

    So just to confirm the responses, Instead of running the C wire from each thermostat to each zone valve, I can just jump the C terminals on each zone valve, and then run 1 wire from the last c terminal on the zone valve, and connect that to the 3 c wires from the thermostat, and then connect those to the C terminal on the transformer? So it would be like 3 c wires from thermostat could be wire nutted to 1 wire, and that 1 wire would connect to the 1 c wire from zone valve and 1 wire from c on thermostat?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,042
    edited October 2023
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    YES

    Actually there is already a C wire on each of the zone valves. There is also a C terminal at the transformer. The C stands for Common, and Common is the return path for all things 24 volts. If you have a load that requires 24 volts, then you need to send R to the load and have a return path back to C. Where you connect to the C is not going to matter.


    on the top diagram I have added the blue wire to show that you can connect the C from the thermostat to any C in that circuit fed by that transformer.

    Your bottom pic shows that the common goes to each zone valve already (in Blue). So if all the thermostat wires come back to the transformer location then connect all the C wires there. If the thermostat wires come back to the individual zone valves , then connect the C wire there.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • fixerguy
    fixerguy Member Posts: 3
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    Hi. I just wanted to circle back and say thank you for the help and advice. I connected the wiring according to the advice given here, and everything is working great, and so far nothing is smoking. I also installed the smoke keeper as advised by edtheheaterman. It's a great feeling of accomplishment, nice to save money on the self install and hopefully the new wifi thermostats will be able to save some fuel and money by turning down the heat when away from home. Thanks again.