Nest thermostat wiring

[M4martin]

 

 Please help. I have heat pump and need to know how to correctly wire this thermostat.

 

[CoolingWizard]

@M4martin , your Nest Learning Thermostat is wired correctly for a heat pump.  If you are not getting heat when turn the system on for Heat, you might need to change the settings of the O/B wire.  Some heat pumps are by default a Heating system, and some are by default a Cooling system.  The reversing valve p, when energized, changes the system from Heating to Cooling or from Cooling to Heating.  About 80% of the heat pump systems sold are O models, which are Cooling models.  The other 20% are B models which are heating systems. 

If you perform the system tests after installation, and you test cooling and it puts out hot air after 10 minutes, or if you test heating and after 10 minutes you get cold air, your heating pump reversing valve mode needs to be changed.  

AC Cooling Wizard

[M4martin]

Thank you for your response. Can you be a bit more specific about how to change wire connections?

[CoolingWizard]

If the picture of your Nest backplate, it was wired correctly. There is no need to change a wire. Just change the setting for the O wire.

If your system starts to blow cool air when your Nest thermostat is in Heat mode (or if it blows warm air when it's in Cool mode), change the settings for orientation of your heat pump.

Nest Learning Thermostat

1.  On your thermostat, go to Settings.
2. Select Equipment.
3. Select Continue > Continue.
4. Select Heat Pump.
5. The Nest Thermostat defaults to an O setting for heat pumps. 
   • If the O option is highlighted, select B.
   • If the B option is highlighted, select O.
6. Select Done.
7. To make sure the issue is resolved, test your heating and cooling again.

AC Cooling Wizard

[M4martin]

So, it was set to O. So I changed it to B. Do I set the mode to heat or heat/cool? And should the fan be coming on in the outside unit?

[M4martin]

Should the white wire be in W1 or W2aux?

[CoolingWizard]

When you have a Heat Pump system, on the extremely cold nights the heap pump might need help.  The electric heating strip in your air handler are the Auxiliary Heat and the control wire goes to W2. As for the mode this is a personal choice. If you set Heat/Cool in theory you would never need to switch the system in winter versus summer. 

AC Cooling Wizard

[M4martin]

Still not putting out hot air. Can you please send a picture of the correct wiring?

[CoolingWizard]

Here is an example of a Heat Pump with Auxiliary Heat. 

I hope this helps. Your white wire is in W2.  

AC Cooling Wizard