My neighbor stopped by to mention my heat pump had frost on it, and that the unit might be low on freon. I just checked some web pages I found during my last heat pump research session, and one in particular (Heat pumps 101) mentions that frost is normal for a heat pump, and it will defrost itself if necessary.

I don’t have time today but I’m going to evaluate Pann and Building Automation for heat pump inspections over the next month or so.