Nest - N72 error - Common Wire

[windward]

I installed a Nest in the house a few months ago and everything was working fine when the AC was running. Once I turned the heat on, the nest could not keep it's battery charged and I am getting an N72 error. I have an AC Air Handler in the attic and a a two wire boiler in the basement.

After many hours with Nest tech support, they recommended I connect a common from the AC transformer (Not the common on the boiler). Apparenely when you are using two separate systems, it always tried to charge the batteries with the AC side of the Nest. I had an extra wire, so I could easily connect it to the AC common.

Before I plug the Nest back up, does anyone see any issues with the wiring?

Thanks in advance!!

 

[bobdole4u2]

How's this boiler thing work? Is it in no way connected to the ac evaporator blower? How does it blow warm air through the house?

Sent from my SM-G930V using Tapatalk

 

[windward]

Boiler is for hydronic baseboards. It is not connected to the air handler.


Sent from my iPad using Tapatalk

 

[windward]

I hooked up the Nest last night with the wiring as I had drawn it out. Seems to be working fine.

 

[LS6 Tommy]

How's this boiler thing work? Is it in no way connected to the ac evaporator blower? How does it blow warm air through the house?

Sent from my SM-G930V using Tapatalk

Boiler is for hydronic baseboards. It is not connected to the air handler.

X2. Boilers make hot water or steam, not hot air.

Windward's diagram is fine. His setup with baseboard and central AC would be my preferred setup if I had everything my way in my house.

Tommy