Nest Learning 3rd Gen wiring and setup for Stage 1 and Stage 2 Heat

[Eagle155]

I have new home with the following HVAC system.

GE HVAC

AIRHANDLER - UUY36ZGDAB2

HEAT STRIP - UAZEH10A

HEAT PUMP - AUH2436ZGDA (Variable speed)

THERMOSTAT - PRO1 T721

I purchased a Nest Learning 3rd Gen thermostat and asked him to use it, but he could not get the Stage 1 (Heat Pump) and Stage 2 (Electric Heat Strip) heat to work, so he installed a PRO1 T721.

Will the Nest work with this system so that stage 1 and stage 2 heating will run together as this system is designed to operate given the fact that this heat pump will operate down to -10 DEG and if so, how would it be wired and also setup within the Nest itself? Will the jumper on the existing thermostat be used on the Nest? Can the Air handler be engaged after the heat pump can generate warm air? With current thermostat it engages the air handler before the air is warm so it is blowing cold air for a couple minutes until the heat pump generates warm air. 

Thank you for any help, advice, guidance I can get.

[Patrick_Caezza]

@Eagle155 

Give this wiring a try.

Brown - W/E to W2 (jumper to W2 not needed)

Orange - B to OB

Blue - C to C

Red - R to Rc

Green - G to G

Yellow - Y to Y1

You will need to change the OB setting.

Nest Learning Thermostat

1.  On your thermostat, go to Settings.
2. Select Equipment.
3. Select Continue > Continue.
4. Select Heat Pump.
5. The Nest Thermostat defaults to an O setting for heat
   pumps. 
   • If the O option is highlighted, select B.
6. Test your heating and cooling again to make sure the issue is resolved.

[Eagle155]

I installed as directed and it only blows cold air. When going thru the setup the Nest confirmed the wiring was correct and correctly identified the equipment. I did the Nest equipment test for the heat pump and the aux heat and both blew cold air.

[Eagle155]

@Patrick_Caezza

Thank you for your help.  Wiring is spot on. Once I figured out the B option, it worked!  Thank you, thank you!!

[CoolingWizard]

@Eagle155 , you old thermostat is set up for a B model heat pump.  Your heat strips are currently wired to W/E emergency heat with a jumper to W2/AUX auxiliary heat. When you setup your equipment in the Nest Learning Thermostat you set the change over vale to B.  The default is O type heat pump. Place the W/E wire on to the Nest W2/AUX.  Place the Red wire on the Nest RC terminal. 

AC Cooling Wizard

[CoolingWizard]

@Eagle155 

You need a better understanding of how your Heat Pump, Thermostat and Air Handler work together.  When there is a heat pump application there is an electric heat strips added to the indoor air handler.  Control of these is typically given to the Thermostat and the outdoor unit defrost control board.  
Under thermostat control, the thermostat waits 30-minutes fate the heat pump is running to see if the ambient room temperature is still dropping.  If it is, the thermostat will energize the W2/AUX wire which signals the air handler to energize the heat strips to boost the heat output.  

Under defrost control, if the outdoor unit detects ice buildup, it will activate the defrost controller, the defrost controller will change the reversing valve, and signal the air handle to turn on the auxiliary heat.  The defrost controller will run a specified time and then return the reversing valve back to Heat Mode, and turn off the auxiliary heat. 

This just leaves Emergency Heat. When you have enough conductor wires, there can be a with on W/E or E. This wire attaches to the air handler at the same point the W2/Aux wire attaches.  The difference is that the Emergency Heat mode can to turned on by the homeowner.  This is useful in the case of the winter time if your heat pump fails, it needs to be repaired. You still have some heat   

AC Cooling Wizard

[Eagle155]

Thank you for your help! And the explanation on how this system is supposed to work. Once I figured out that it was on the default O option and I changed it to B, it worked wonderfully. Love the Nest!