Gen 4 Next Not Calling Aux Heat When In Regular Heat

[dc95]

During a period of extreme cold, my HVAC started to blow cool air when heating. I hadn't had issues all winter, and my HVAC unit is 10 months old. I called an HVAC technician, who said my system is fine but the issue with Google Nests is that their algorithm sometimes won't call for the aux heat kit to turn on and will instead opt to heat the house slowly. Last night my system took 10 hrs 18 minutes just to keep the apartment at 69 degrees. Prior to when we started experiencing issues, it would only need to heat for 1 to 2 hours at a time. These are all coming from my Nest app. How can I get my Nest thermostat to call for Aux Heat if the regular heat pump outside needs assistance to heat the house? I don't want my system to run for dozens of hours a day.

[Patrick_Caezza]

@dc95 

All thermostats that use the standard 24Vac control scheme are just fancy switches that turn various system functions on or off.

If the HVAC is taking a long time to heat or cool, and it is not short-cycling, the issue is with the HVAC unit. So long as the thermostat is calling for heat or cooling, it is up to the HVAC todo the work.

Now, with that said, what type of HVAC do you have? Furnace? Heat Pump? or something else?

How is the thermostat wired? Is there a C wire?

[dc95]

I have an electric unit with a hear pump. There is a C wire and it shows the C wire is connected when I look at the wiring settings. 

I tend to agree that the thermostat isnt the problem since this became an issue suddenly. But the technician is certain it’s an issue with "the fancy" thermostat. I think they just don’t want to do the work. 

[dc95]

@Patrick_Caezza

[josephjames8]

That makes sense in extreme cold Nest can be too conservative with aux heat. Manually setting a higher temp or switching to Emergency Heat during cold snaps usually helps. Appreciate you sharing the app data too, very helpful info (almost as useful as finding solid tips on JJ77 ).

[dc95]

I don't mean for this to come across as snippy, but why does it make sense that the Nest would be conservative with aux heat? Why wouldn't it just heat my home as instructed? Happy to share any app data with you, let me know what you would like screenshots of and I'll post them here.

[cloudpragmatics]

I dealing with a similar issue, but mine includes the compressor never going into defrost mode (which should be out of the thermostats control). That being said, I just installed a Gen 4 to replace a Gen 3 and I noticed in the setting that "Heat Balance" is set (which wasn't a bad thing in the past), but I also just saw that "Compressor lockout" was set to "Always" (which means always use compressor regardless of temperature). I've reset this to "Temperature" and setting a floor temp to lockout the compressor on super-cold days. While this may not be directly related to the problem your having, you might want to check those settings (in settings/equipment/compressor lockout). By locking out the compressor at a certain temp (15F ?) the Aux heat is forced to be the only heat source.

[cloudpragmatics · Accepted solution]

Also, I think turning off "Heat Pump Balance" may give you more control settings for when Aux Heat turns on. It looks like the only place to do that is on the app itself under "settings/equipment/heat pump/use heat pump balance". If you turn this off, "Advanced" will light up and give you a lot of configuration settings.

[dc95]

@cloudpragmatics This is the answer. I found this the other day on a Reddit thread as well. I went to turn off "Heat Pump Balance" which permits the thermostat to activate the heat kit/aux heat, allowing it to heat my place faster. Now even though temps reach single digits at night, the hvac unit is only running for 1-2 hours at a time periodically through the night to heat my place instead of running for 11 hours to reach the desired temperature. If it gets colder I will also look at your compressor lock out suggestion. Very annoying that I had to spend days to figure out the answer, but yes, toggling the heat pump balance off setting did the trick. Thank you!

cloudpragmatics

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