topic Re: Problems with thermostat with separate furnace and AC/ Air Handler in Nest Thermostats

Problems with thermostat with separate furnace and AC/ Air Handler

Stefanfmann — Sun, 05 Mar 2023 17:44:20 GMT

I can't figure out getting my Nest to work:

I have a gas furnace in the basement- Triangle Tube Prestige

I have run thermostat wires to the Nest - RH, W1 and C

With this it functions just fine and heats according to plan.

- But

I have a 1st floor Air Handler with Roof Top AC

When I connect this together with the Heating System, Using the RC, G and Y1, the thermostat displays the error:

power may be out to my system and that I need either an RC or RH wire even though it shows on the connected wires screen that both of those wires are connected.

I appreciate any help.

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Patrick_Caezza — Sun, 05 Mar 2023 20:04:10 GMT

Which Nest Thermostat do you have?

Only the Nest Learning Thermostat is compatible with separate heat and cooling systems.

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Stefanfmann — Sun, 05 Mar 2023 21:02:42 GMT

@Patrick_Caezza it is the learning thermostat. it's a few years old (I gave up trying to figure out and let it sit for a while)

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Patrick_Caezza — Mon, 06 Mar 2023 21:41:47 GMT

@Stefanfmann

Can you post a picture of the current thermostat's wiring?

Is it currently using just one thermostat or two?

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Jenelyn_O — Thu, 09 Mar 2023 23:40:33 GMT

Hi there,

Thanks for reaching out. Could you please provide the photo of your Nest Thermostat wiring asked by Patrick_Caezza? It will help us to move forward.

I appreciate your help, @Patrick_Caezza.

Best,

Jenelyn

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Stefanfmann — Fri, 10 Mar 2023 20:10:26 GMT

@Patrick_Caezza , @Jenelyn_O

Here is the wiring for one connected system- the heat. This works.

Triangle Tube Prestige. I don't believe the common wire was required for this- I only connected it because of the errors displayed when the AC is also connected.

https://www.dropbox.com/s/yo26a14fd7p73zy/IMG_9558.JPG?dl=0

Here are photos of the wiring with two systems connected, and the various error messages that come up. - again, the heat alone works but both systems connected doesn't.

https://www.dropbox.com/scl/fo/6r4rxaj8ffswtr1n1sfz3/h?dl=0&rlkey=282c5rut95ti5r4nywbxeag1j

Last time it showed me "No Power Detected, Rh or RC wires required" but you will see that it detected those wires as connected.

This time I reconnected the AC, it is giving me the "No Power to Common Wire Detected" message.

ugh.

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Stefanfmann — Wed, 15 Mar 2023 12:43:24 GMT

let me know if you are able to view the images @Patrick_Caezza , @Jenelyn_O

thank you.

Stefan

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Jenelyn_O — Wed, 15 Mar 2023 19:03:49 GMT

Hey Stefanfmann,

Thanks for the additional information. Could you please try to remove your C wire and check if it will ask you to have one? If it's requiring you to have a common wire, try to strip and cut your C wire before putting it back to its terminal. Make sure that your breaker is off before touching your wires. Let me know how it goes.

Best,

Jenelyn

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Stefanfmann — Sat, 18 Mar 2023 21:34:27 GMT

Hi Jenelyn,

With the heat system connected only, having removed the C wire, there is no error displayed.

The errors come when both heat and AC systems are connected.

Thank you.

@Patrick_Caezza , @Jenelyn_O

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Jenelyn_O — Wed, 05 Apr 2023 19:37:38 GMT

Hi Stefanfmann,

Thanks for the update. I'm sorry for the delay. I just want to check if you're still encountering the issue. Please let me know as I'll be willing to assist you further.

Regards,

Jenelyn

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Jenelyn_O — Sun, 09 Apr 2023 16:19:37 GMT

Hi there,

I wanted to follow up if you still need help. Please let me know if you’re still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks,
Jenelyn

Re: Problems with thermostat with separate furnace and AC/ Air Handler

Jenelyn_O — Mon, 10 Apr 2023 16:37:39 GMT

Hello Stefanfmann,

We haven't heard from you in a while so we'll be locking this thread if there is no update within 24 hours. If you need assistance or want to discuss topics, feel free to start a new thread.

Best,
Jenelyn