I had a new Carrier Heat Pump (2.5 ton 15SEER) with variable speed air handler installed in my 1850 sq ft house in September 2008. I have noticed that when the overnight temperature drops below 30F the unit will run all night with out shutting off (7 hours). I called the installer so they could look at the unit and they said nothing was wrong. Long on times like that are OK and I shouldn't be concerned. Last night the temperature dropped to 20F and the unit ran for 12 hours without shutting off. I am concerned that something is wrong (maybe incorrectly sized?). I listen to other heat pumps in my area and they cycle on and off while mine stays on. I keep the temperature set at 68 with no setback. I also have a carrier edge thermostat that cycles the AUX heat if the temp has not raised after 25 minutes. I would like to get others input on this. Is the 7 - 12 hour on time OK? Is the unit sized correctly?

I had a new Carrier Heat Pump (2.5 ton 15SEER) with variable speed air handler installed in my 1850 sq ft house in September 2008. I have noticed that when the overnight temperature drops below 30F the unit will run all night with out shutting off (7 hours). I called the installer so they could look at the unit and they said nothing was wrong. Long on times like that are OK and I shouldn't be concerned. Last night the temperature dropped to 20F and the unit ran for 12 hours without shutting off. I am concerned that something is wrong (maybe incorrectly sized?). I listen to other heat pumps in my area and they cycle on and off while mine stays on. I keep the temperature set at 68 with no setback. I also have a carrier edge thermostat that cycles the AUX heat if the temp has not raised after 25 minutes. I would like to get others input on this. Is the 7 - 12 hour on time OK? Is the unit sized correctly?

Follow-up. Unit cycles off for 30min after on for 12 hours overnight then back on for less that 1 hour and now off.

I'm having the same problem.. what have you done to resolve your issue?