I am hoping that somebody can help me figure out the algorithm that the Lennox iComfort Touch thermostat uses to blend in AUX heat when controlling a heat pump (XP17). The system is a couple of years old now (when the system was installed the iComfort was brand new) and I'm still puzzled by some of the decisions it makes with regards to using the aux heat.
So the aux is expensive to operate and I would expect it to make every effort possible to avoid turning it on however the iComfort seems to be more than willing to crank up those expensive heat strips. If it is very cold outside (20ish degrees) the system runs cycles lasting about 25 minutes, about 15 of which it will run the HP alone and then it'll turn on the heat strips until the cycle is finished. That's fine; at 20 degrees outside I don't expect the heat pump to keep up by itself. However I've seen it turn on those aux strips even when it is 40+ degrees outside, the HP is putting out plenty of warm air by itself, and it is only a few minutes into the cycle! At all instances of the heat strips turning on the thermostat is still holding steady at its set point of 68 degrees so it isn't like it is falling behind or has caught a cold draft.
Does anybody familiar with the original iComfort Touch know the logic behind the aux blending? Are there any settings changes I could make to mine to make it more efficient? Do the newer iComfort thermostats handle the aux in a more efficient manner? I like how the iComfort thermostat exposes all of the system settings/error codes and don't really want to replace it but are there any others that would heat the house with greater efficiency?