Gen 4 support for natural gas/heat pump

[Rstrle]

Hello, I was early to the Nest party. We had a Nest 1, at some point we upgraded to a nest 2. The wiring mount says Model 02A. It has worked fine since 2015. I’m upgrading to a Gen 4 (G5AJK). We have an American Standard dual fuel heat pump that also works perfectly. On the old unit I had a white wire on W1 and a black wire on W2. When I wired the new unit up like that I got an error message that told me those wires were redundant. I disconnected those wires and the gen 4 unit seems to cool fine. In the old unit I was able to set a point 32 degrees I think, where the unit would run on gas. Above that it would run on heat pump. How do I get that functionality on my model 4?

[GabrielaG]

Hi @Rstrle,

Thanks for contacting the Google Nest Community. I understand you've upgraded to the Nest Learning Thermostat (4th gen) and want to control when your system switches from the heat pump to the gas furnace for auxiliary heat. I'm glad to help you.

I appreciate the information you provided me about the changes you made with your wiring and the previous error code. To provide you with accurate troubleshooting steps, please help me out by answering the following questions:

• When did you install the Nest Learning Thermostat (4th gen)?
• Did you notice any error codes after disconnecting the W1 and W2 wires?
• Could you please send me a picture of the wiring for the current Nest Thermostat?

If you have any additional information to share, we would greatly appreciate it.

Regards,

Gabriela

[Rstrle]

Hello Gabriela, I did install the Nest 4th gen myself. I also installed the Gen 2 myself. On the Gen 2 Next everything worked as expected. When I installed the Gen 4 Nest I wired it the same. I got an error message. I believe it was an error 433 redundant wiring or something like that. I called Nest support and the support person had me disconnect the White W1 wire and install the black W2 Aux wire. That solved the error message and I believe aux heat will turn on (It's warm here and I had to turn the set point up to 80 degrees.) But, my issue remains that I can't set my secondary heat point.

I can't upload a photo here. This is how the Nests are wired.

Gen 2

Y1 - Yellow	W1 - White
Y2 - Brown	W2 AUX - Black
G - Green	C - Blue
OB - Orange	* - Empty
RC - Empty	RH - Red

Gen 4

Y1 - Yellow	W1 - Empty
Y2 - Brown	W2 AUX - Black
G - Green	C - Blue
OB - Orange	* - Empty
RC - Empty	RH - Red

Thanks for your help.

[GabrielaG]

Hi @Rstrle,

Thank you for your reply. I appreciate the detailed information you provided about the wiring on your Nest Learning Thermostats. I'm glad to continue assisting you.

Please try the following wiring connection:

Y1 - Yellow	W1 - White
Y2 - Brown	W2 AUX - Black
G - Green	C - Blue
OB - Orange	* - Empty
RC - Red	RH - Empty

After reconnecting all the wires on your Nest Learning Thermostat (4th gen), please remove the device from the Google Home app, perform a Factory Reset, and then set it up again in the app. 

Let me know if you have any questions or need more information.

Regards,

Gabriela

[Rstrle]

I will try this later today and report back.

[Rstrle]

I did this and the nest thermostat gen 4 accepted it and let me set when to turn on aux heat. However, during setup the thermostat wasn't recognizing the brown wire on Y2. I did as instructed and made sure it was connected in the thermostat housing OK. I clicked next and the thermostat finished the setup process. I guess we'll hope for the best?