topic Re: Nest thermostats 3 Zones, 2 wires, No C wire, How to wire Nest Power connector?? in Nest Thermostats

Nest thermostats 3 Zones, 2 wires, No C wire, How to wire Nest Power connector??

Schico — Thu, 28 Jul 2022 14:59:39 GMT

I have a new IDEAL Combi boiler with three zones for heat. All 2 wire. (R & W), They are powered by a 24v transformer. No Zone control box, So the circuit is: Transformer -> Thermostat(S) -> Zone Valve(s) - Transformer. The (T,T) connection that activates the boiler is triggered by the "end switch" from either of the 3 zone valves. This is independent of the power for the Transformer/Thermostat/Zone Valve circuit. The Zone valves are the wax expansion type and take a couple minutes to activate. I do not think the boiler is to be activated until a zone is actually open. SO trying to insert the Nest power connector it looks like I would have the R from the transformer go to both of the R wires on the power connector and the R that goes to the Thermostats. (4 wires together). The W coming back through the Nest-Zone Valve(s) would go to white on Nest Power connector (on the Left). The C and W on the Right would go to the W on the transformer. Does this sound correct? Attached is a diagram. I do not know how the Nest Power Connector is spoofing the thermostat to make it happy with 2 wires so I am not sure it will work. Two thermostats in the Heat only Zone are Basic Nest thermostats and have the N260 error. The other is the Nest Learning thermostat and also has a totally separate AC system in it (3 wire R, Fan, Comp) + the R&W from the boiler. This one seems smart enough to be happy with the power it has. One basic Nest has no access to other wiring without Sheetrock and paint matching activities. (external wire is unacceptable) So i would really like the power adapter to work.

Re: Nest thermostats 3 Zones, 2 wires, No C wire, How to wire Nest Power connector??

Jeran — Fri, 19 Aug 2022 17:47:51 GMT

Hey there Schico,

I apologize about the late response, thank you for your patience on this! Were you able to get that Nest Power Connector attached? If not, in this scenario, I would recommend that you contact a Nest Pro. Unfortunately, we have limited resources when it comes to HVAC specifics.

I look forward to your response, and if you have any other questions or concerns for me, please let me know.

Best regards,
Jeran

Re: Nest thermostats 3 Zones, 2 wires, No C wire, How to wire Nest Power connector??

Schico — Fri, 19 Aug 2022 18:04:39 GMT

Thank you for taking the time to respond.

I have not tried it again yet. It is not an uncommon system. I spoke to several people at work and they have similar systems. Simple transformer powers Thermostat which opens zone valve, which when open, closes the switch to activate the boiler. If I understood just what the power adapter does i could figure it out.

Re: Nest thermostats 3 Zones, 2 wires, No C wire, How to wire Nest Power connector??

Schico — Thu, 27 Apr 2023 14:14:21 GMT

I had figured this out and finally. EACH THERMOSTAT/ZONE NEEDS IT OWN POWER CONNECTOR.

I was trying to use it to power 3 zones at once. I did not find this info posted anywhere specific.

Would have saved dozens of hours for me.

Re: Nest thermostats 3 Zones, 2 wires, No C wire, How to wire Nest Power connector??

Jake — Tue, 02 May 2023 19:53:33 GMT

Hey Schico,

I am glad to hear you were able to resolve the issue, and everything is good to go from here. With that being the case, I a going to go ahead and lock the thread in 24 hours. Let me know if you have any further questions from here, as I would be happy to review.

Best regards,

Jake