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Problems with thermostat with separate furnace and AC/ Air Handler

Stefanfmann
Community Member

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.

11 REPLIES 11

Patrick_Caezza
Platinum Product Expert
Platinum Product Expert

Which Nest Thermostat do you have?

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

 


To ensure that I see your reply, please tag me using @Patrick_Caezza

@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)

 

Patrick_Caezza
Platinum Product Expert
Platinum Product Expert

@Stefanfmann

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

Is it currently using just one thermostat or two?


To ensure that I see your reply, please tag me using @Patrick_Caezza

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

@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.

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

thank you.

Stefan

Jenelyn_O
Community Specialist
Community Specialist

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

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

Jenelyn_O
Community Specialist
Community Specialist

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 

Jenelyn_O
Community Specialist
Community Specialist

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

Jenelyn_O
Community Specialist
Community Specialist

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