2-Stage Heat Pump with AUX

[Discovery3751]

Hello,

I have a Trane system that has a 2 stage heat pump for heating and AUX heat. I am not sure it is activating the 2nd stage when attempting to heat the house during colder temps before switching over to AUX. I am also missing the heat pump balance in the options.

I currently have wires in Y1, G, O/B, Rc, W1, W2/Aux, C

[CoolingWizard]

@Discovery3751 

With your system, the primary heat is the heat pump and the heat pump when it runs, and it needs to be defrosted outside. It will activate the auxiliary heat to keep the air warm while trying to defrost the ice outside using the heat from the inside of the house. You only have a heat pump balance when you have what they call a dual fuel system and that would be a heat pump for primary heat and a gas furnace for secondary heat. This is the only time that you would have a heat balance option.

AC Cooling Wizard 

[Discovery3751]

That seems reasonable. In the settings, does the"dual fuel" mean that when it hits that temperature outside it will switch to only utilizing the heat strips or will begin to utilize them intermittently? The system also has 2 stages of heating using the heat pump prior to switching on Aux heat. The second stage is labeled as Alt 1 in the system with heat strips being Alt 2. It seems like the system doesn't utilize Alt 1.

[CoolingWizard]

@Discovery3751 

there is no such thing as auxiliary heat one and auxiliary heat too when it comes to a thermostat in the conventional HVAC system. You may have two 10KW heat drip packs in your air handler however, they are controlled by the air handler and the sequencer and not the thermostat.

The auxiliary heat is attached only to the W2/AUX terminal of the Google Nest Thermostat. 
Duel Fuel means you have two types of heat. Electric Heat from the Heat Pump and Gas Heat from the Furnace.  The balance is knowing when to change from Heat Pump heat to Gas Furnace heat. Typically this around 25°F. With the highly more efficient heat pumps produced in current days. This temperature typically will be closer to 15°F.  in reality, you have to make some calculations of energy consumption to heat output and cost of that energy consumption to find that crossover point. Each home and each system within a home is unique to that home and those calculations have to be made. But like I say a rule of thumb is 25°F. 

AC Cooling Wizard

[Discovery3751]

@CoolingWizard 

Right, but I only have the heat pump and the heating strips and don't have dual fuel even though the thermostat indicates that. My understanding is this system has 2 settings for the heat pump when heating, a lower power setting and a higher power setting during times it gets cold. I also have the Aux heat with the heating strips. It is possible that the problem I am encountering is the system thinks I have multiple fuel sources when it is only the heat pump and the heat strips. What appears to be happening is it hits a low temperature and turns off the heat pump and switches to only using the heat strips.

I attached two photos in the album below to show what I am seeing in the nest app.

https://photos.app.goo.gl/hBYm8r3tcdLdNAYC6

[ITDUDE71]

Have you tried removing W1 and doing a reset to change the duel fuel?

[CoolingWizard]

@Discovery3751 

what is causing your problem? Is you have a heat pump but you have a wire in W1. There should only be one wire for the auxiliary heat, and it should be in the W2 position. Anytime there’s a wire in the W one and you have a heat pump (OB) And you have a wire in W one the system assumes you a duel fuel system. You need to go to the air handler and investigate where the W1 wire and where the W2 wire are landed on the indoor air handler control board.  

AC Cooling Wizard

[ITDUDE71]

I have the same problem, I have turned off my balance but it still won't go past the thermostat indoor temp.

[CoolingWizard]

@ITDUDE71 ,

please post a picture of the nest thermostat back plate. Show me what wires you have attached. Also upload the screenshot you took of the old thermostat before you disconnected the wires. I’m sure we can get this figured out. 

AC Cooling Wizard