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Heat pump wiring issue...

awolf21
Community Member

I'm trying to get a Nest Learning Thermostat to work.
I have a Trane heat pump. (My system is electric power only, no gas.)
Before I purchased, Nest support told me my system WAS compatible and I was given wiring instructions.
Installed it, and cooling works, but heat does not turn on.
Images of my Trane thermostat wiring, the Nest wiring I was told to use, and the wiring on my air handler controller board follow...
I've spent about 20 hours trying to figure this out and was first wrapped up in the "does white go to W1 or W2/aux?" discussions. But I think this would affect only resistive electric (backup/emergency) heating, not basic heat pump heat.
Now I'm focusing on "Nest doesn't work if you have O AND B wires."
I will be pissed if this is true, as Nest confirmed compatibility with my system.trane thermostat.jpgnest.jpgcontroller.jpg

6 REPLIES 6

awolf21
Community Member

May or may not be relevant, but I went to the Ecobee support site and checked their compatibility in this situation (O and B and also a C wire) and their site says "O to O/B, B to C" and specifically says this should work with Trane TCONT thermostat -- which is what I have. This IS the wiring Nest gave me. (I'm assuming Nest and Ecobee are similar/identical in terms of compatibility.)

I've also been told... "pay no attention to wire color, it's all about what happens at the controller board", which is why I included that photo.

Thanks for any advice.

awolf21
Community Member

@Patrick_Caezza

Hi. Can you take a look?
Thanks.

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

@awolf21 

 

Trane always uses the B terminal for the C wire, so you're okay.

Try moving the White wire from W1 to W2/AUX and set it as an AUX Heat. The black wire is for Emergency heat and should be set as such on the * terminal.


To ensure that I see your reply, please tag me using @Patrick_Caezza

Patrick:
I moved white from W1 to W2/Aux.
Black was already on *
https://ibb.co/SJDZwVm     shows settings consistent with what you said.
Still no heat when I crank up desired lower temp.
Don't know if it is relevant, but the Nest displays the desired temp range that I set but shows "Heat Stage 2."
Why Stage 2? Shouldn't it show basic "Heat Pump Heating""?
https://ibb.co/Nnz1zB6     shows recognized equipment.

About to toss in the towel, but if you have any other suggestions...
Thanks.

@Patrick_Caezza

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

@awolf21 

Give this a try.

 

If your system starts to blow cool air when your Nest thermostat is in Heat mode (or if it blows warm air when its in Cool mode), change the settings for orientation of your heat pump.
 
Nest Learning Thermostat On your thermostat, go to Settings .
  1. Select Equipment.
  2. Select Continue > Continue.
  3. Select Heat Pump.
  4. The Nest Thermostat defaults to an O setting for heat
    pumps. 
    • If the O option is highlighted, select B.
    • If the B option is highlighted, select O.
  5. Test your heating and cooling again to make sure the issue is resolved.

To ensure that I see your reply, please tag me using @Patrick_Caezza

@Patrick_Caezza

So, heating DOES work!  YES!
The critical change was white being moved from W1 to W2/Aux.
But heating is SLOW. In the range of 1 - 1.5 degrees/hour.
With my old Trane thermostat, when heat came on it was fast and loud (air flow at the vent).
Heat may have even worked with prior wiring of the Nest (white to W1), but I didn't realize it was working because it was slow.
So maybe I'm getting heat with the Nest, but not the right stage of heat?
Or maybe my Trane was more "aggressive"?