I need an expert out there to tell me if my heat pump is working properly. Outside temp is 27 degrees. Indoor ambient air temp (read from both thermostats) is 66 degrees. Thermostat is set to 68 degrees. Heat pump seems to run and run for long periods, in some cases hours on end with very little increase in temperature. In fact, vent temp reading with my laser thermometer is 69 degrees, no wonder it's not improving much.

If I bump the thermostat to anything 3 degrees or more above the current ambient air temp (in this case setting it to 69 degrees), a little "aux" symbol appears, which I presume to mean there is a toaster grid somewhere heating up (this of course means $$$$). When aux is indicated, the vent temps shoot up to 89 degrees within a minute or so. At this point, within 20 minutes the ambient air temp will rise about 1 degree, which then shuts the aux feature off, and the cycle continues with the fan blowing for the next hour or so until the temp again drops enough to invoke the aux feature.

Is this behavior normal? My rather crude understanding of a heat pump is that it "reverses" function in order to remove heat from the air outside the house and release this heat into the inside of the house via the furnace blower. Sort of like a reverse air conditioner. Am I right? If so, logic would dictate that efficiency would drop off sharply as the temperature outside drops, since there is very little heat to remove from the outside air. But this seems a little out of the ordinary. In fact, I don't remember it behaving this way last year. But then again, I don't think 27 degrees is normal for North Texas (Chicago transplant, still figuring out the weather here).

Does this type of operation sound normal, or should I schedule an appointment with an HVAC guy? Are there some simple things I can check myself before doing so?

Thanks in advance!

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