How do I connect these wires to nest 3rd generation.

Mircofe — Sat, 07 Jun 2025 18:45:29 GMT

Hi, My old thermostat has 1 wire called COM linked to the power, then it has a group of wires called FAN which Iincludes another COM, I,II,III.
I read that I should connect like this:
COM (power) : C
COM (fan): G
I : empty
II : Y2
III: *

What do I do with the fan I?

Thanks all for your help!

Re: How do I connect these wires to nest 3rd generation.

Derickf — Wed, 11 Jun 2025 05:43:58 GMT

Hi @Mircofe,

Thanks for reaching out to the community. I understand you have questions about how to connect your Nest Learning Thermostat (3rd gen) to some wires of your HVAC system. I'm happy to help.

To gather the necessary information, please answer the following questions:

What type of HVAC system do you have?
Could you please share a picture of the previous thermostat’s wiring?

I'll be waiting for your reply.

Best regards,

Derick.

topic How do I connect these wires to nest 3rd generation. in Nest Thermostats

How do I connect these wires to nest 3rd generation.

Re: How do I connect these wires to nest 3rd generation.