Nest install with Honeywell zone valve.

[BobL]

Installing new nest thermostat to operate a Honeywell zone valve , system has 2 wires r/w.  When connecting nest without power connector (external transformer-24v 75va) it operates the zone valve with no issues, just don't have motion sensing, battery charging and there is a code on display.  When I connect the nest power connector to the system it does not operate the zone valve.  I am reading 16v going to the zone valve on a heat call which I believe is not enough to open the valve.  I read 27v coming from transformer to power connector.  Doesn't matter if jumper is in or out. Any ideas?

[Houptee]

How are you wiring the power adapter to the zone valve?

The 3 wires on adapter lets call them R3 W3 C3 go to 

R3 to the R screw on transformer (disconnect the existing R wire that is on the transformer and goes to the Nest and splice to the R on adapter)

W3 goes to the Yellow zone valve wire. (disconnect the existing W wire coming from the Nest from the yellow and splice it to W on adapter).

C3 goes to the other yellow wire on zone valve (there will be 3 wires all connected Yellow, C3, and the existing wire that goes back to the other screw on the transformer aka the Common side)

Leave the jumper cap installed in the adapter. That is only removed if you are not using the system transformer for power, you are using your transformer so the cap stays in.

[BobL]

Thanks for the reply. Yes that is the way I have the nest wired.

[Jeff]

Hey BobL,

I wanted to check in on this and see if you got this sorted out or to see if you were still needing some input on this. If you're still working on things on your end, let me know what else you have tried and I'll be happy to jump in and start helping.

Thanks,
Jeff

[BobL]

Jeff: Yes I was able to get it working properly,  not sure what the issue was as I went over the wiring many times and then it started working and not had an issue since. Thanks for the help.

[Dan_A]

Hi BobL,

I'm glad that you're able to work this out. As we got our resolution here, I'm going to mark this one as resolved and will be closing this thread after 24 hours. Please feel free to open up a new thread if you have other questions or concerns.

Cheers,

Dan