I have the following system York 3-Ton Affinity HP and gas furnace with a Honeywell 8321 thermostat.
I noticed on the thermostat had the following readings: 72F indoors and 40F outdoors. The HP turns on because I had the heat rating at 72F. The heat pump stays on for ~2 hours before it stops. During the entire 2 hours the HP was operating, the indoor temperature reading was 72F indoors. I was surprised that the HP was operating for such a long time and did not give up. I was wondering how and when does the thermostat determine that the HP cannot meet the heating demand of the house and start up the gas furnace to meet the demand of the home?
Is it normal to have the thermostat read 72F indoor temperature with the thermostat set to turn on the heating cycle at 72F and have the HP run for more than 1 hour before the system recognizes that it can't keep up with the heat demand?