Problems with thermostat with separate furnace and AC/ Air Handler

[Stefanfmann]

@Jenelyn_O

My original post that you locked is not resolved.  I had not heard from you in weeks and then didn't check it for a couple weeks.

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.

@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)

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 

@Patrick_Caezza , @Jenelyn_O

[Patrick_Caezza]

@Stefanfmann 

When you have a dual transformer system like you have, the C wire must come from the cooling side and NOT the heating side.

So what you need to have connected is this.

Heat

Rh, W1

Cooling

Rc, Y1, G, C

[Stefanfmann]

@Patrick_Caezzathank you.  I was wondering if that was the case.  Of course the Cooling wiring is more difficult to access.

Do you know if the problem would be sidestepped by using a C Wire power adaptor from the heating side to create a different C wire?

[zoeuvre]

Hi Stefanfmann, 

I wanted to stop by and see how I could help.

As Community Specialists, we occasionally do a bit of housekeeping to keep the conversations in our community fresh and relevant. This includes locking threads after a period of inactivity. Going back, some 3rd party C wire adapters can cause problems or damage your Nest Thermostat, even if they claim to be Nest compatible. We recommend using a Nest Power Connector to ensure compatibility and best performance with your thermostat.

Thanks for the help here, @Patrick_Caezza. 

Let us know if you have any other questions.

Best, 

Zoe

[Stefanfmann]

Thanks @zoeuvre and  @Patrick_Caezza  

can I use the nest power connector attached to the heating system to supply C wire that should be coming from the cooling side?

Thank you,

Stefan

[zoeuvre]

Hi there, 

Thanks for getting back to us. Yes, you may use the Nest Power Connector attached to your heating system's control board to connect your cooling system. However, if you are having difficulty accessing your cooling system, you may ask for assistance from our Nest Pro technicians, who are trained in installing Nest Power Connectors.

Regards,

Zoe

[Stefanfmann]

@zoeuvre thank you.  the access issue is just because the air handler is boxed in and I would have to cut open a portal for access.  I just need to debate with myself which task is easiest.

Stefan

[Patrick_Caezza]

@Stefanfmann 

Question. If the air handler is boxed in, how is its filter changed?

[zoeuvre]

Hey Stefanfmann, 

I wanted to check 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.
 

Thanks,

Zoe

[Jenelyn_O]

Hi there,

I'm sorry about the previous thread that has been locked due to inactivity. I just wanted to follow up if you still need help. Please let us know so we can further assist you. 

I appreciate your help, @Patrick_Caezza and Zoe.

Best,

Jenelyn

[Jenelyn_O]

Hey there,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know. 

Regards,

Jenelyn

[Patrick_Caezza]

@Stefanfmann 

Do you have any spare wires in the thermostat cable for the cooling side? If you do, you can use it to create a C wire. You could use the Google Nest Power Connector if you don't.