Nest is not detecting Power (Rh) Showing error that power is not connected. Please help.
Installing Nest 3rd generation thermostat from Old Trane Weathertron Thermostat (Mercury one)
New stat wiring:
Old stat wiring:
Nest error:
Electrical – Installing Nest 3rd generation thermostat from Old Trane Weathertron Thermostat (Mercury one)
electricalthermostatwiring
Related Solutions
I believe you need to move the red wire at the Nest to the Rh terminal. Rh is 24v from the Heating system. The Rc terminal is 24 volts from the Cooling system. Change that around and see if your issue is fixed.
Based on this wiring diagram, this looks like a multistage heat pump thermostat (provide control of a two-stage heating/one-stage cooling heat pump system).
From left to right in your picture:
- W2 = Aux. Ht. Relay
- G = Fan Relay
- R = Power
- X = (Note says terminal labeled C/X on some models, and based on diagram, I think your assumption of common wire is correct)
- E = Em. Ht. Relay
- Y = Compressor Contractor
- O = Cool Changeover Valve
Based on those wires, and this wiring from the Nest Pro Installer Guide, I think you'll wire it as a 1 Stage Heat Pump with Aux heat and Emergency Heat
So if we link up your current wiring to Nest:
- W2 -> W2/Aux (Auxiliary Heat Relay)
- G -> G (Fan Relay)
- R -> Rc (24VAC power)
- X -> C (24VAC Common Wire)
- E -> * (Star: E)
- Y -> Y1 (Compressor Relay (Stage 1))
- O -> O/B (Heat Pump Changeover Valve)
Best Answer
While you do not state if this is a heat pump unit - the wiring indicates it is..
Your NEST screen shows that Rc (24Volt power for Cooling Circuit) is connected and Rh (24Volt power for Heating Circuit) is not connected, yet in your picture for wiring hook up your red wire is connected to the Rh line (so how does Rc get power and show a connection?). The Nest is either reporting wrong - or you have changed something between pictures.
You can run a jumper across from Rc to Rh since you only have one Red wire. Unless your NEST configuration allows you to to do that through software - if the software does this for you when you select heat pump - I would venture the red they will have you connect to Rc and program jumper to Rh it might aut connect it as well.
You will also need to make sure you specify in the NEST system that you have a HEAT pump unit - this might be a reason Rh does not work and Rc does.
Why you have BLACK X2 to HUM (which I think is humidifier) - I don't know. X2 is supposed to be AUXilliary Heat and would be connected to W2.
You can see my post here for Thermostat wiring proper color code and also what the individual labels mean - what circuit they are for.