Nest and Bryant Evolution

[wang313]

I purchased a Nest learning thermostat with remote sensor to replace the Bryant thermostat that came with my HVAC system.  I only have 4 wires, marked A B C and D, but they are obviously the typical yellow, red, white, and green wires.

I've placed them into the Nest slots for G, Y1, W1, and Rh, but I have no control over the HVAC system. The fan turns on and runs continuously, and I can't turn it off. The air conditioning and heating will not turn on at all.

Has anybody else encountered this situation? I am thinking something needs to be rewired at the HVAC unit itself, but I'm afraid to start playing around in there. Please help, this is so frustrating!!

[Lycoming360]

We need more information to help with this.    What brand and model number is your air handler?   Do you have a heat pump? What is the source of heat?

My own experience is that INSTALLED wire colors do not necessarily match industry standards -- you may need to need to visualize where each wire originates in the air handler.

[wang313]

It is a Bryant 80v Plus 2 stage gas furnace and a Bryant AC unit (don't recall the model but think it is single stage). It's not a heat pump.

I took pictures of the wires and where they enter the air handler. The incoming wires from the thermostat go to the ABCD box. But there are also connections on the side (second pic) which have the regular markings for G, R, Y, W, etc. The wires that are currently in those slots all appear to be outgoing to the AC unit. None of them are connected to the thermostat wires. Any ideas?

 

 

[Patrick_Caezza]

You can't go by the color of the wires as there is no standard.

Terminals labeled as A, B, C, and D are normally for a proprietary interface that is not compatible with any of the Nest thermostats.

[wang313 · Accepted solution]

I had an HVAC technician out here yesterday, and he confirmed Nest will not work with my system because of what you stated above. I will have to return it, unfortunately.

[Ryan_G]

Hi wang313,

Thanks for posting here in the Google Nest Community.

It's sad to hear that your system isn't compatible with your HVAC unit. If you have any other questions or concerns, let us know by creating a new thread as this one will now be locked.

Best regards,

Ryan