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Khatva · 04-15-2022

I have a Taco ZVC-405-4 with priority, and a set of 4 Nest learning thermostats on 4 radiant heating zones. I have been running with 2-wires fine for a few years, but there have been some battery issues and I want to use the C wire, which the thermos...

Khatva · 04-30-2022

The controller didn't fix it. Further investigation seems to imply some issue with the C wires, which doesn't make much sense as there are 4 different runs of cable and all show the same behavior (so it's not a wire break or other problem somewhere),...

Khatva · 04-26-2022

My HVAC person is going to replace the ZVC in the hope that that fixes the 25v R to C problem.

Khatva · 04-15-2022

I did measure the voltage. R to W gives the expected ~25 VAC but R to C shows only ~12 VAC (and similarly C to W shows ~12 VAC). Is that why the Nest is unhappy? Is this a problem with the Taco ZVC?

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Nest Wiring with Taco ZVC-405-4, common doesn't work?

Re: Nest Wiring with Taco ZVC-405-4, common doesn't work?

Re: Nest Wiring with Taco ZVC-405-4, common doesn't work?

Re: Nest Wiring with Taco ZVC-405-4, common doesn't work?