Mapping AUX/E

[Daneel]

Hello,

I just bought the Nest Thermostat 2020 (not a Learning Nest thermostat) to replace a basic thermostat. The Home app tells me it is not compatible with my setup even if an expert on this forum told me it was.

I have wires O/B, Y, R, C, G, AUX/E on my existing thermostat while I have OB*, Y, R, C, G, W on my Nest thermostat.

The AUX/E is a unique wire used for emergency heating.

Should I map AUX/E to W?

Thank you in advance.

[CoolingWizard]

@Daneel, 

can you show us the picture you took of the old thermostat and it’s wiring so we can verify what terminals were used and how your system was wired?

AC Cooling Wizard

[Patrick_Caezza]

@Daneel 

A picture of the original thermostat's wiring would help.

The AUX/E terminal on the original thermostat controls the AUX heat, and if the thermostat has an Emergency Heat switch, it allows you to use the AUX heat as Emergency heat.

You would normally connect the AUX/E wire to the W terminal on the Nest and set it as Aux heat.