I have a standalone (non-dual fuel) electric Heat Pump/AC. I tend to notice the issue of cold air blasting about every hour/when condenser enters defrost mode more when it is below freezing. I have the lockout set to 17 degrees. This has been happening since the new system was installed about a year ago and 3 techs can't figure it out. One thread I saw said you need to let the thermostat know that it is OK to run AUX the same time as the heat pump but I can't figure out how to do that.

My setup:.

https://imgur.com/a/ACtSjfm.

https://imgur.com/a/eHdDNMc.

https://imgur.com/a/mrtW4ZW.

Question from user SignoftheTimes23 at hvacadvice at reddit.com.

Answer:

Might be the nest, might just be an actual problem with the aux heat or defrost board, or wiring.

Answer from user lost_horizons at hvacadvice at reddit.com.

blowing cold air when heat pump enters defrost mode