Wiring new thermostat

[Mchait]

Wiring.  Compatibility. Thermostat A 4 wires.  Red Green Gray. White.  (Heat and air conditioning).  Thermostat B. Wires.White  and Red. Heat only.     Do these need a C wire.  

 

[Egeddes]

Hi.  Yes if you are putting a Nest thermostat you will need a C or common wire. You will need a Google power connector.  I've attached the photo.  You can get these almost anywhere.  Instructions are easy to follow but it's always a good idea to have a professionals HVAC person put  it in. 

Now., the 2 wire system (Red & White) will never be able to handle an AC even with power connector.  You need at least 3 wires plus a common to do that.  If you do end up running new wire, do like a 7 wire.  That way you will have plenty of wires as technology advances.

[zoeuvre]

Hi folks,

@Egeddes, thanks for chiming in. 

@Mchait, thanks for posting here in the Community forum and for showing interest in our Nest Thermostats. Could you post a clearer and more detailed photo of your current thermostat wiring configuration so we can take a deeper look? You may use our Compatibility Checker to help you determine if a Nest thermostat is compatible with your heating and cooling system.

I'll look forward to your response. 

Best,

Zoe