{I am re-posting here as it seems to be a more appropriate place}
Hello everyone. Great Forum!

I have a lennox heat pump (X13, I believe...about 2 years old) mated with a 15 year old Heil Gas forced air furnace and a Honeywell 7400 thermostat. I am on a dual energy system and have a changeover relay that automatically locks out the heat pump when the temp hits -13C.

On to my question:
Lately, I have noticed that when it's colder out (between -6 and -10C) when the thermo calls for heat, the heat pump starts up, runs for about 30 to 45 seconds then shuts off and the gas comes on. I am pretty sure this is not happening because the temp drop is too low, because often the thermo starts calling for heat when the ambient and set temp are the same.

I don't seem to have this problem when the temp is warmer than about -5C, the heat pump seems to put out good heat (air from vents is fairly warm).

I imagine I will have to call a technician to look into this- just wondering if there is anything I can check for myself and would also like to know what to expect from the technician.

Thanks in advance for your input.