Nest Basic thermostat can't run auxiliary heat strips along with outdoor condenser

[Larry_napa]

I have the basic nest thermostat.   I have a heat pump with auxiliary heat strips that the thermostat is set up for.   All works well, except when I attempt to engage my auxiliary heat, only the heat strips and fan run however, the outdoor condenser is suppose to run at the same time to produce the max heat possible.    I did an electrical test, and the thermostat only engages the green (fan), and white (heat strips) - but does not engage the Yellow wire for the outdoor condenser unit. Is this a fault in the Nest Basic thermostat?   Note, the Emergency Heat option works as should.       I am using the G, R, Y, C,W (and O/B, set to O).

Thank you for any assistance you can provide.

[screamingbanche · Accepted solution]

Same issue here. Website says the basic nest thermostat is compatible with heat pumps with auxiliary heat. My issue is that the auxiliary heat never engages even when set 10+ degrees above space temp. Electric heat works as should during defrost cycle and if emergency heat is selected. But not both heat pump and auxiliary heat at the same time. I chatted with support yesterday and they either couldn't, or wouldn't tell me if thermostat is compatible with auxiliary heat. Just tried to push me in the direction of calling a local nest pro service company. I am a service tech. I did read another post where system was set up as dual fuel and apparently that system is functioning as it should. I need to try this to confirm. Until then, I'm sticking with my original thought which is that the basic nest thermostat is not compatible with auxiliary heat. Most everything I'm reading says the basic thermostat is not compatible and at minimum, the Learning thermostat is required. I was kind of assuming/hoping that the thermostat would engage the white terminal when auxiliary heat was needed but so far I haven't seen it. So again, I do not believe it's compatible with auxiliary heat.

[Larry_napa]

I did just purchase the 3rd generation Nest Learning thermostat and was able to get the Auxiliary heat to work while running the outdoor compressor (engaging the yellow wire).   This setting is under the "Equipment" in Settings.    It takes the outdoor temperature from our local weather forecast (via Wi-Fi) to determine if it should kick-on, then you will see "Auxiliary Heat" displayed on the thermostat and Nest App.   However, unlike the ability we have in the Basic Nest, you do not have the option to use "Emergency Heat" in case your outdoor compressor is broke (go figure).       Going back to the Basic Nest... I just re-installed it again for a final test, that is,  I've selected in the Google Home app, under Thermostat Settings:  "Temperature Preferences"..."Heat Pump Balance"...("use heat pump balance" switch to "On."  Then I'm playing with "Balanced" or "Max comfort."     By doing this, I'm waiting for the outdoor temp to fall below 40degrees, then I will check if the heat strip comes on along with the outdoor compressor.     So, standby, I'm waiting for a cold morning to test this out.

[screamingbanche]

Looking forward to hear your findings. I want to purchase the basic thermostat just so I can play around with configuration. And possibly try the dual fuel setup.

[Larry_napa]

I was just successfully able to use the Auxiliary Heat with outdoor-compressor at the same time on my Basic Nest Thermostat.     I'm not sure what changes occurred since I  last reported having issues when the Aux heat activation turned off the outdoor-compressor.  
Please note, I used the settings via the Google Home app and not the thermostat settings.  To simulate this:- I did a factory reset- Outside temp was around 55 degrees, however I'm not sure what the wi-fi/internet told the Basic Nest what temp was being used for the thermostat computation. So, this is what I did to make this happen: 

-  I set "Settings..Temperature preferences..Heat Pump Balance to OFF"

- I set "Settings..Thermostat..Compressor lockout to "Aways" (aways use compressor)

- I set "Settings..Auxiliary heat lockout..to 65 (ie, if outdoor temp is below 65 degrees)

- I set the indoor temp from 66 degrees to 72 degrees.

I confirmed this test run by using an Amp Meter to see the power consumption increase when heat strips were engaged (also the app and Nest thermostat displayed "Aux Heat.").  So this proves to me the yellow wire (outdoor compressor) and white wire (heat strips) were engaged at the same time.
I'm thinking the Thermostat setting needs to be set around 5-7 degrees higher than the current indoor temperature for this simulation to work.
I'll continue to test out the "Heat Balance" settings  when the weather gets cold enough.