topic Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires? in Nest Thermostats

Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

doc9983 — Mon, 02 May 2022 02:37:28 GMT

I have a dual fuel system. Current thermostat has 8 wires, Two of the wires are S1 and S2. Nest doesn't use these wires. Do I simply tape these. I have seen some diagrams that show the pink wire going in Y2 and the black wire going to the *.

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

Patrick_Caezza — Mon, 02 May 2022 03:08:35 GMT

The S1 and S2 wires are from an external temperature sensor, and none of the Nest use it. Just tape them off.

Please post a picture of your original thermostat's wiring, and I will try to provide a wiring list.

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

doc9983 — Mon, 02 May 2022 03:49:05 GMT

Current Wiring

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

Patrick_Caezza — Mon, 02 May 2022 04:13:52 GMT

Give this a try.

White - E to W2/AUX (jumper to AUX not needed)

Black - S1 - not used

White - S2 - not used

Red - RC to Rc (jumper to RH not needed)

Orange - O/B to OB

Yellow - Y to Y1

Gren - G to G

Blue - C to C

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

doc9983 — Mon, 02 May 2022 13:56:33 GMT

Thanks for your help. I have seen several suggested configurations. Most agree with yours with one exception. The white is showing going to W1. Could this be because I have dual fuel and not auxiliary heat?

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

Patrick_Caezza — Tue, 03 May 2022 04:00:31 GMT

You have a heat pump system and the yellow (Y) wire is what changes it between heating and cooling.

The white wire is for AUX heating and that is done on the W2/AUX terminal. You can use the W1 if you want, but the correct wiring is on the W2/AUX and why it is labeled as AUX

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

doc9983 — Tue, 03 May 2022 15:22:43 GMT

Thank you for all your help.

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

doc9983 — Tue, 03 May 2022 17:14:53 GMT

Nest says dual fuel setup should be done by a trained professional. Is there a guide available to take me through the setup?

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

MelbaDT — Wed, 11 May 2022 04:14:08 GMT

Hey folks,

Appreciate your responses, Patrick_Caezza.

doc9983, I'm afraid we can't provide a guide for this type of system as this is best done by a professional. Please get in touch with an HVAC technician or a local pro. They'll be the best one to talk about this.

Best,

Melba

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

MelbaDT — Sat, 14 May 2022 05:43:33 GMT

Hey doc9983,

Checking back in should you still have some questions here.

Best,

Melba

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

MelbaDT — Fri, 20 May 2022 06:23:19 GMT

Hi,

I haven't heard from you in a while so I'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community.

Best,

Melba

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

doc9983 — Fri, 20 May 2022 13:34:51 GMT

I was able to do the install myself with a little guidance from YouTube. The nest is up and running perfectly. I love it. So glad I made this choice!! Thanks for all your help.

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

MelbaDT — Tue, 24 May 2022 03:43:33 GMT

Hey doc9983,

Awesome ― glad to hear that you've managed to have it working. Give yourself a pat on the back for a job well done!

Cheers,

Melba

Re: Wiring for dual fuel system with eight wires. What do I do with the S1 and S2 wires?

MelbaDT — Fri, 27 May 2022 03:59:19 GMT

Hi,

Best,

Melba