Heat Pump Thermostat question

douglasr1December 30, 2013

I have a heat pump w/ electric back up.
I have thermo stat set at 68, unit runs, thermo stat says 68, keeps running.
This happens only when it is below around 32 degrees.
seems like at night when the temp is in the 20's the heat pump runs all night with out turning off.
Could the stat be not calibrated, or be bad, letting it run after it has met its desired temp?
I'm new to heat pumps , as my last home had a gas furnace and ran until desired temp was met then turned off

any ideas

Thanks

Doug

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dadoes

32ðF-ish apparently is your system balance point ... the outdoor temp at which the heat pump's output matches the ambient heat loss ... so it runs continuously to maintain the target temp of 68ðF. That's not necessarily a bad thing. Depending on how low the outdoor temp gets (20ðFs), it's cycling the electric supplement to help maintain the 68ðF target.

    Bookmark   December 30, 2013 at 5:12PM
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douglasr1

Thanks for your imput.
So even when it's 20's outside it will run continuously to try to get heat out of the air? , and that's ok ?
doesn't harm the unit to run nonstop?
and its cheaper to let it run nonstop than have the back up heat on?

    Bookmark   December 30, 2013 at 5:43PM
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dadoes

Harm the unit, no. There's heat coming out of it, yes ... just not enough to fully satisfy the thermostat for cycling off. Your backup likely is already running some of the time. If the room temp dips far enough below the 68ðF setpoint (67ðF to 66ðF depending on the differential) the backup will trigger to make up the difference to almost 68ðF. The heat pump will continue running while the backup is on in such a case. The backup in this case is referred to as "supplementary" or "auxiliary."

You can optionally set the thermostat mode switch to Emergency Heat to forcibly prevent the compressor from running ... only the backup will run to maintain the target room temp.

But if there is any heat coming out of the heat pump at all, it's reasonable to leave it at normal operation ... the back up will run only as needed to "supplement" the heat pump.

If there's an ice storm happening, sleet or snow or humid conditions that promote very frequent / heavy icing and defrosting of the outdoor unit, it's reasonable to switch to Emergency until the conditions ease.

    Bookmark   December 30, 2013 at 6:54PM
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douglasr1

Thanks for your knowledge,
make me feel a little better knowing what you have said here

    Bookmark   December 31, 2013 at 9:04AM
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mike_home

I am not the heat pump expert so I will defer to others who are more knowledgeable. But do those of you who own heat pumps think it is normal for the condenser to run constantly when the temperature is below 32 degrees? We are getting frigid temperatures in the north east during the next several days. This would be a good test.

My questions are:
- Are you sure the auxiliary heating is working properly?
- When was the last time the heat pump was serviced, could it be low on refrigerant?
- Perhaps the heat pump is too small for the heating load. How big is the house and what is the size of the heat pump? Have you tried heating the house above a temperature of 68?

I think you are not going to be happy when you see your next electric bill. Any information on electric bills and rates would be interesting.

    Bookmark   December 31, 2013 at 9:16AM
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douglasr1

hi
yes the aux heat works properly
had it serviced in november and refrigerant was good
from what i was told, heat pumps are not sized for heating, they are sized for cooling and it does a good job cooling the house.

i spent about $80.00 last month to heat the house

    Bookmark   December 31, 2013 at 12:58PM
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bus_driver

My heat pump is paired with a gas furnace and the dual-fuel controls switch to the furnace at 28 deg. The heat pump handles that setup just fine. Located in the mid South.

    Bookmark   December 31, 2013 at 3:39PM
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