I have a 2.5 ton XL15i with a 3 ton air handler. It's a little over a year old. I noticed last Nov and Dec that, whenever heat was called for, the thermostat showed "auxilary heat ". Even when the temp outside is about 62, when I set the thermostat for 68, for instance, the outside unit runs and a few seconds later, aux heat shows on thermostat? My heating bill was very high last nov and dec. Is there something wrong with the system? Shouldn't the heat pump run w/o aux heat on?