Nest N72 Error Split System

[BryanD]

Error N72: "Power wire Rh detected. No connection to equipment." 24VAC confirmed.

Thermostat had been working fine since I installed C from the air handler to power the Nest. 

From our standard, ducted air conditioning system we have four wires:

• Y
• G
• Rc
• C

From our very basic, boiler-and-radiator based gas heat system we have 2 wires:

• W
• Rh

A few things to note:

• The Tech Info diagram on the unit itself shows "power" greyed-out on Rh. 
• Testing with a digital multimeter between Rh and W1 shows over 24VAC consistent.
• When I wire W1 and Rh together the boiler zone calls for heat and kicks on so the wire to the thermostat is fine
• I have three nest thermostats; two nest learning 3rd generation on AC and Heat and a Nest E 1st running heat in the basement. First floor heat works fine. Second floor heat won’t turn on this year.

[Chobes]

Hey, I have this exact issue. Although sometimes I get the E102 error as well. I called Google and they said they think I have a bad base. Of course I’m out of warranty. I’ve had this hooked up the same way for over 2 years and now I have the problem. Everything is correct on the heater side. My basement nest E works fine for heat. I wonder if there’s a way to trick it to keep the heat on the main floor

[RicMaker]

I purchased a new base had the same problem with it, out $50.00

[Chobes]

Yea I am not very confident it will work. I did someone else in another forum with a similar issue and replacing the base did fix their problem. I will update when I have more. I temporarily replaced it with my old mercury thermostat. No battery required haha

[RicMaker]

I was able to get mine to run by putting a short piece of wire in W1.

Moving the White wire from W1 to W2.

Now the heater works as Heat2

[BryanD]

Unfortunately this still isn’t kicking my heat on; I’m probably going to have to put my Nest from the basement upstairs and go without heat down there. These things have become giant pieces of crap. I remember loving them but why can’t they just work... Does Google even respond on here anymore?

[Chobes]

I’m confused as to how this would work. The problem is that Rh is greyed out. Not W1…

[BryanD]

W1 wire is just a short wire that doesn’t connect to anything? Just holds the connector open so it thinks a wire is connected?

[RicMaker]

Yes, its just a 1 inch piece that goes nowhere, but without it you get a error code

[BryanD]

I wish that worked. Heat 2 was running but my thermostat still didn’t kick on.

[RicMaker]

Heat 2 kicks on 3 degrees higher, try that

[BryanD]

It’s trying to run just not; says it’s heating heat 2 on the Nest. Just not the boiler on.