Heat pump with auxiliary heat but setup as dual fuel

[thanhhuong]

I have a heat pump with auxiliary heat (electric furnace) system and recently switched to Nest from our old thermostat. The HVAC tech did the wiring and setup for us, just in October when it starts to get cold, I notice there is no Heat Pump Balance option in the app.

Digging further, I notice that the setup is Dual Fuel (Gas), not Auxiliary Heat and the wiring is at W1, not W2. The HVAC tech told me that setup is fine as well, but I'm not feeling confident. Before with the old thermostat, if it takes long to reach desired temperature, or if it's too cold, auxiliary heat will kick in. With this dual fuel setup, it seems it will only kick in at -10 degree Celcius.

Question: will this setup harm the system in any way, beside unable to control the auxiliary heat as I wish?

Thank you all!

[CoolingWizard]

@thanhhuong , that HVAC tech is indeed incorrect in setting up your Nest thermostat for you. You need to have the wire that he placed in W1 moved to the W2 position. The Nest thermostat requires auxiliary heat to be on W2. you’re also going to have to redefined the function so that it goes from a dual fuel system to a heat pump system. If there’s a wire on the OB and there should be a wire on the OB, and you move the wire to W2, The Nest Learning Thermostat should determine automatically detect the system as a Heat Pump with Auxiliary Heat. 

AC Cooling Wizard

[thanhhuong]

Thank you. I moved the wire to W2 and there is a were on OB, but the app doesn't change the system from Dual Fuel to Heat Pump with Auxiliary Heat. Try reset the Nest thermostat as well. Used the Test function to test the Auxiliary Heating but no air coming out (I heard a click when the test began, like it tried to turn on but no air out of the vent). The heat pump is working though. 

Any other step I should take?

Thank you

[CoolingWizard]

@thanhhuong , allow me to kind of explain how the system of heat works. When the system begins to heat, it doesn’t turn the blower on immediately because what it tries to do is get the heat exchanger warmed up enough so that basically the heat when the air comes out is warm and not cold. Let’s talk about how to change your system from dual fuel to a heat pump system only.

You need to go into SETTINGS and then to EQUIPMENT, then choose CONTINUE twice. Next choose HEAT TYPE and select Heat Pump. By the way, before getting here you will see a pictorial of the back plate with wires attached to different labels. Make sure the wedge with the letter on it is all green and there are no yellow ones if they’re yellow ones let me know.

AC Cooling Wizard

[thanhhuong]

Thank you.

1. Pictorial of the back plate with wires attached to different labels: There is no green or yellow, but all letters are in white and different colors for different wires.

2. When I choose HEAT TYPE: The menu options are Forced Air (my system)/In-floor Radiant/Radiators.

3. In EQUIPMENT SETTINGS menu: The options are HEAT TYPE/HEAT PUMP/DUAL FUEL/PRO SETUP/BACK. So somehow Nest still recognizes my system as Dual Fuel even though the wire is at W2 now.

4. When doing the test for ALTERNATIVE HEAT, I leave it on for a while but the fan doesn't run. When testing for HEAT PUMP HEAT, the fan turns on right away.

Any other advices are appreciated. Some photos below.

[CoolingWizard]

@thanhhuong 

when you get into heat type, you need to scroll down and highlight the word heat pump and select it by pressing the display. Until you select heat pump, it won’t change

AC Cooling Wizard

[thanhhuong]

When I get into Heat type, the options are Forced Air (my system)/In-floor Radiant/Radiators (see photos).

The system already recognizes the Heat Pump, but for the second heat source, it recognizes it as ALTERNATIVE HEAT (Dual Fuel) - not AUXILIARY HEAT (Electric furnace). 

When I select Heat Pump - It only asks if the heat pump type is O or B - which is set correctly at O.

Any other ideas?