I have read about some people successfully using their heat pumps down to 15-20 degrees. I'm hoping my new system will be as successful. Does the VisionPRO learn when the HP can't keep up and turn it off or does it always run the heat pump and just add the AUX heat? Does it only disable the heat pump when the outside temp goes below the HP shutout temp?

Also, does the heat pump control defrosting by itself or is there something in the t-stat that controls it?

Essentially, I want to use my HP as much as possible but I also want my HP disabled if it isn't contributing anything.