topic Re: thermostat compatibility check in Nest Thermostats

thermostat compatibility check

jianpingjpzhang — Mon, 21 Nov 2022 18:54:46 GMT

Please let me know if the nest thermostat is compatible to my existing wiring system. Many thanks

Jianping

Re: thermostat compatibility check

CoolingWizard — Mon, 21 Nov 2022 20:35:42 GMT

We need some more information. Do you have batteries in that thermostat ?

Ken, The AC Cooling Wizard

Re: thermostat compatibility check

jianpingjpzhang — Tue, 22 Nov 2022 04:39:05 GMT

Yes, Ken. There are two AA batteries in my current thermostat.

Re: thermostat compatibility check

CoolingWizard — Tue, 22 Nov 2022 04:46:33 GMT

Try this, remove the batteries of your old thermostat, remount it and see if it power up. If it does you have a common wire present.

Ken, The AC Cooling Wizard

Re: thermostat compatibility check

jianpingjpzhang — Tue, 22 Nov 2022 05:27:51 GMT

no. it doesn't power up after i remount it back w/o batteries

Re: thermostat compatibility check

CoolingWizard — Tue, 22 Nov 2022 18:23:09 GMT

So that means you do not have a common wire present. And the B wire is for the heat pump reversing valve.

Ken, the AC Cooling Wizard

Re: thermostat compatibility check

jianpingjpzhang — Tue, 22 Nov 2022 18:51:30 GMT

okay, so the nest thermostat would not work on my existing system, right?

Re: thermostat compatibility check

jianpingjpzhang — Tue, 22 Nov 2022 18:55:11 GMT

by the way, the G nest thermostat package (i haven't open it yet) says it includes two 1.5v AAA batteries. does it mean i don't necessary need a C common wire which is to supply power to the thermostat?

Re: thermostat compatibility check

CoolingWizard — Tue, 22 Nov 2022 20:01:51 GMT

In certain situation is the nest learning thermostat third generation, has a ability to use a backfeed of one of the unused control wires to keep the battery charged. However, for the most efficient charging capabilities, you could do is still use a nest thermostat would add a nest power connector to make sure you do. You have the power to keep it charged. In some situations there may be an extra unused wire in the cable behind the wall. The thermostat that can be repurposed for the Common.

Ken, The AC Cooling Wizard

Re: thermostat compatibility check

CoolingWizard — Tue, 22 Nov 2022 20:05:28 GMT

That thermostat you have uses batteries, which is kind of the traditional way programmable, smart thermostats were powered. So yes, it could be used. You would just have to change the batteries when they get low. That little black wire that has jumper and yours makes me think that there is a black wire, unused inside the cable behind the wall.

Re: thermostat compatibility check

Markjosephp — Sat, 26 Nov 2022 19:34:46 GMT

Hello folks,

I wanted to ensure that everything was covered here.

Thanks for assisting here, Ken. Big help!

@jianpingjpzhang, I found a helpful article about how common wire, or C wire, works that would help your system to consistently deliver power to the thermostat. Feel free to let us know if you have more questions in mind.

Best regards,

Mark

Re: thermostat compatibility check

Markjosephp — Tue, 29 Nov 2022 19:40:53 GMT

Hi jianpingjpzhang,

I wanted to see if you still needed help. Please let us know if you have any other questions or concerns.

Thanks,

Mark

Re: thermostat compatibility check

Markjosephp — Wed, 30 Nov 2022 19:43:38 GMT

Hello jianpingjpzhang,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any additional questions or concerns before I lock this thread in 24 hours.

Best,

Mark