Can you hook up to one nest thermostat

[JamesD11]

Can you hook up to one nest thermostat to , two separate system IE ( AC unit has ducts , Oil fire furnace is baseboard radiators , To operate thermostat wires to one nest thermostat ? 

[laurentbourg]

Yes you can, with a Nest learning thermostat 3rd generation. 

[JamesD11]

What is the wiring diagram for that , as right now it doesn't work 
Thank you

[laurentbourg]

Please upload a picture of your old thermostat wiring as well as your Nest wire plate wiring

[JamesD11]

Two stat wires 18/2 from heat red to R , white to W on old stat 

Second stat wire 18/4 coming from Air handler in attic  Yellow to Y , Green to G ,  Red to RC  , White to W on old stat , There were two thermostats , one for Heat and one for AC . 

So how would this be wired on one Nest learning thermostat ? 

Right now on new nest stat White is to W and Red is to RH , only heat is hooked up now , on nest stat .

Thanks James