God I hate a heat pump. At least mine. I'm better off ignoring it, but sometimes I sneak a peak. Stupid me. Mine enters aux heat a lot. I know as I can hear it click in. I've been ignoring it all winter because I know my unit is old and maybe weak, but lately it has warmed up and the damn thing is still kicking in. Today I hear it kick in (it had been running, not sure how long) so I go look. Oddly, the ambient temperature was showing as my programmed 'set' temperature on my Honeywell RTH7400D digital unit. Why would the aux heat kick on if I was at the set temperature? Silly me for asking, but I am. While pondering this the heat pump finally shuts off. A few minutes later it kicks in again and I run over to see. Sure enough the indoor temp shows 70 and the unit is set to 70. This time no aux heat, but I again wonder what conspiracy is at play to eat my utility dollars? The damn thing has been running 30 minutes now and I've been measuring the temp of the vent output at 81 degrees. It is 54 degrees outside. My unit knows it is 70 because the display says so, and it knows it is supposed to keep the heat at 70. So if both are 70 why has it been running for 30 minutes?!?!?! I had this same wacky bahavior with the old school mercury thermostat and had hoped this digital one would help. It hasn't. My 1987 'Energy Star' home (HAHAHAHAHAHAHAHA! Jokes on me!) is cold natured but isn't full of leaks, holes in the walls, etc. I do have lots of older inefficient windows, but at least they are double pane. What the hell is going on? It is still running...this could be very normal, I usually ignore it and just let the damn thing run and try to shut it out.