I recently installed a Nest thermostat (the new one) in my home, but I’m having trouble getting it to work properly. My system appears to use a gas furnace (Payne) and an external AC (ThermalZone TZAA-330-2A) for heating and cooling.
The previous Honeywell thermostat had a red wire going into Rc (there seems to be a little metal plate shared between this and the otherwise-empty R terminal), a yellow wire going into Y, a blue wire going into C, a white wire going into W (which also had an O/B label), and a green wire going into G (photo). I connected all the wires to the same terminals in the Nest. After some searching, I supposed that since I don’t have a heat pump (my AC’s model number confirmed this) and I have a gas furnace, I should use the W terminal for the white wire.
But the system doesn’t appear to properly send out warm air when it’s supposed to be heating. It keeps sending cold air.
Additionally, the Nest thermostat has designated the heat source as electric instead of gas, despite my selecting gas during setup. The setting is grayed out in the Home app, and Nest Settings > Equipment doesn’t show me any way to change it.
I’ve tried putting the white wire in the W and O/B terminals on the Nest:
When in the W terminal, the thermostat sends out cold air.
When in the O/B terminal and setting the switch to “B” in Home app settings, the thermostat acts strangely, sending cool air at first but then sending warm air, and I can feel the house get more humid. When set to “O,” it seems to only send cold air but it’s possible I didn’t wait long enough before switching. I suspect that it's using the furnace and pulling cooled outside air and that it shouldn't be in the O/B terminal. But I don't know.
I’m hoping someone can help me figure out what’s going on and how to fix it. Any advice would be greatly appreciated!
