can i use one Nest learning therm to control both baseboard hot water heat and central A/C?

[argio]

if yes, is there a wiring diagram?

[Houptee]

Yes but the nest likes to see the power come from Rc and C (the air handler transformer).

If you connect power to Rh also coming from the boiler transformer it will confuse the nest and it wont work.

So there is a workaround that requires a relay be installed with the 24v AC coil connected to the Rh and W from the nest. Then the wires on the boiler R and W go to the normally open contacts of the relay.

When Nest asks for heat the coil energizes with 24v and the contacts close hence connecting R and W on the boiler which turns it on.

If you search youtube for relay on nest ,you will find some videos about it.

[EdwardT]

Hey folks,

@Houptee, thanks for the help!

@argio, how's it going with your Nest Thermostat? Still need our help?

Thanks,

Edward

[EdwardT]

Hi argio,

I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.

Thanks,

Edward

[EdwardT]

Hi argio,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,

Edward