topic Old Thermostat wiring in Nest Thermostats

Old Thermostat wiring

Tyndale1 — Sat, 18 Feb 2023 17:32:46 GMT

I use the Google nest compatibility checker for my old thermostat that is used for my water sourced heat pump and found a wire that is not an option to choose from. I have 7 wires that are connected and they are: R, W2, G, Y, E, O, and X1.

The X1 wire was not an option for the compatibility checker and I was wondering if anyone could give me insight on this.

Thank you,

Re: Old Thermostat wiring

Houptee — Sat, 18 Feb 2023 18:04:44 GMT

X1 might be common but best is go to the system and remove the cover, take a pic of the wires and what terminal screw they go to.

Also look on the back of the cover you remove and there should be a wiring diagram showing the thermostat wiring info and what each terminal screw is for.

Do you have a 2nd backup heat source like a gas furnace or is this a heat pump with only electric coils as backup heat?

@Houptee reply

Tyndale1 — Sat, 18 Feb 2023 18:54:06 GMT

Hello Houptee,

Thank you for helping me out.

I do not have a backup gas furnace.

It would not let me post pictures and reply to you so I just start a new thread.

I'm new to this type of furnace and don't no much about it.

I took pictures of what I believe you were talking about.

Re: Old Thermostat wiring

Tyndale1 — Sat, 18 Feb 2023 18:56:28 GMT

Hello Houptee,

Thank you for helping me out. It would not let me put pictures in this reply to you so I posted a new thread with pictures if you wouldn't mind looking at them and letting me know if those are the right ones that you were talking about?

Thank you.

Re: Old Thermostat wiring

Patrick_Caezza — Sun, 19 Feb 2023 04:22:13 GMT

Your thermostat is compatible with the Nest 3rd Gen Learning Thermostat only.

Try this wiring.

Green - G to G

Yellow - Y to Y1

Blue - E to * (set as emergency heat)

Orange - O to OB

Black - X1 to C

White - W2 to W2 (set as Aux heat)

Red - R to Rc

Re: Old Thermostat wiring

Tyndale1 — Sun, 19 Feb 2023 04:27:16 GMT

Hi Patrick,

Thank you for the response. It is really helpful because I am not smart enough to figure it out on my own. I will give that a try. Thanks again. 👍

Re: @Houptee reply

Houptee — Sun, 19 Feb 2023 05:11:37 GMT

The wiring is not matching up to the thermostat pic you posted.

Where is the cable that comes directly from the thermostat entering the box with the screw terminals? Is it the left cable or the one coming in on the right side?

I don't see any green wire going to the last screw for G (fan) I see green wires but one is wire nutted and the other green on right I cant tell if its connected to anything from the pic.

Also I don't see any aux heat coils shown in the wiring diagram. Bottom corner of the diagram is for the indoor air handler but only shows a fan motor with no aux heat.

Re: Old Thermostat wiring

Houptee — Sun, 19 Feb 2023 05:21:17 GMT

I looked at the wiring pics you posted on the other thread.

I don't see the aux heat or emergency heat shown in the diagram at all.

The wiring info says W is used to trigger the reversing valve it does not show a separate O wire.

So not sure if this is a old thermostat from a prior heat pump system and the heat pump was replaced with what you have now.

The indoor air handler shown in the decal wiring diagram only shows a fan motor no heat coils so maybe the actual air handler you have is different than that decal and it has heat coils.

You would have to post pics of the indoor unit wiring to be sure what you have going on.

Re: @Houptee reply

Markjosephp — Mon, 27 Feb 2023 15:31:36 GMT

Hi everyone,

I've duplicated your thread with the main one here. You’ll receive all updates on this issue on the main thread, and we recommend updating and checking this thread when needed.

Thanks,

Mark

Re: Old Thermostat wiring

Markjosephp — Mon, 27 Feb 2023 15:36:50 GMT

Hello folks,

I wanted to ensure that everything was covered here.

Thanks for the help, @Houptee and @Patrick_Caezza.

@Tyndale1, I hope their replies helped you with your system's compatibility with the Nest Thermostat. How's it going? If there’s anything else we can help you with, please let us know.

Regards,

Mark

Re: Old Thermostat wiring

Jake — Thu, 02 Mar 2023 18:19:40 GMT

Hey there,

I wanted to check in and see if you are still in need of any help. Please let me know, as I would be happy to assist, and answer any questions you may have.

Best regards,
Jake

Re: Old Thermostat wiring

Jake — Fri, 03 Mar 2023 18:23:18 GMT

Hey there,

I wanted to check in, and let you know that I will be locking the thread in 24 hours.

Best regards,

Jake