nest thermostat 4th gen - starting AC when heating is set

[suk]

I've replaced my old Honeywell thermostat of 10+ years old with Nest 4th gen thermostat.

But when the heat is set, the AC is turning on. Not sure what mistake I'm doing. Any help is appreciated.

Note: I bought the house very recently so I don't know my heater type (don't know if it is a heatpump or furnace). The house is 17 years old (SF bay area) and the heater is in roof top attic.

Honeywell Theromostat used RC (red),  OB (white), Y (yellow), G(green) wires.

- Blue wire was never connected.

- there was no RH; only R and RC was there

I've connected these in Nest as: RH (red), OB (white), Y1 (yellow), G (green) wires.

- I didn't connect Blue wire here also.

- I tried connect red wire to RH later to RC - both setups don't trigger heater 

[suk]

pictures of connections:

https://ibb.co/0DjP8NQ
https://ibb.co/CJnrjbQ

[suk · Accepted solution]

Worked with Nest support and they recommended to connect OB (white) wire into W1 which resolved this issue.

[DeboraJ]

Hi @suk

Thank you for reaching out to the community! I understand that you had some trouble trying to set up your thermostat. I appreciate the information about the wiring configuration and your heat pump orientation! This is really useful for our customers, and thank you for sharing the solution!

I’m glad to hear that the issue has been resolved and the thermostat is working properly now. Please let me know if you have any questions or issues that I can help you with. I will be more than glad to assist you.

Best Regards, 

Debora