I have a brand new Lennox XP15 heat pump, an oil furnace and a Honeywell IAQ thermostat. The thermostat is set to lockout the furnace if the outdoor temperature is above -4 degrees celsius (25 f). This seems to be working fine. The question I have relates to when the temp drops below -4 c. I notice that the second the heat comes on, the thermostat reads "AUX Heat On." This will run for a couple of minutes and the word "AUX" disappears and only "Heat On" remains as the heat pump has taken back over. This also sounds fine to me, except the problem is EVERY time the heat comes on, even if it is just a few moments after it has shut off (this happens when it is REALLY cold outside even if indoor temp shows no change), the thermostat reads "AUX heat on" and then eases into plain "Heat on." Is the AUX part supposed to kick in every time the heat comes on when the outdoor temp is below -4 c?
Thanks for your help.