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Old 11-22-2008, 06:24 AM
 
Location: Tennessee
1,339 posts, read 2,504,479 times
Reputation: 710
Default Heat Pump having trouble at this cold temp

Our builder put in a brand new heat pump for us this summer which was great cooling this summer, but this cold is too much.

It got down to 15 degrees and we noticed the house was getting colder by the hour. The heat pump is now in alternate emergency heat trying to warm up the house. We put the temp at 65 to sleep but it got down to 60 and the alternate heat came on. It's now up to 61/62 and is trying to get warmer.

Does anyone else with a heat pump have the same problem heating when the temp outside gets into the teens here?

Now I really feel like I didn't leave the north.
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Old 11-22-2008, 06:52 AM
 
Location: Tennessee
6,300 posts, read 15,477,021 times
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I have a heat pump and it's having no problem keeping it a comfy 70 degrees. Actually, I'm going to go turn it down a little.

I'm afraid you might need to call a serviceman for your unit. Sorry.
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Old 11-22-2008, 07:15 AM
 
Location: Tennessee
1,339 posts, read 2,504,479 times
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We had problems with the original unit cooling in the summer so the builder (warranty just ended in Sept), replaced it with a brand new unit. It cooled perfectly. Now it's my expense. I just thought this might be normal with the temps being so cold outside.
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Old 11-22-2008, 09:26 AM
 
Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week
1,501 posts, read 7,565,097 times
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Heat pumps don't work well when the outside air temp is below 35-ish. They are fairly efficient above 35, but terrible below and it will have to turn to a secondary system of some sort. This is why you hardly see any heat pumps in northern climates (north of Virginia on the east coast).

Tennessee (assuming you aren't in the top of the mountains of East TN - think Seivierville not Knoxville or Maryville) is somewhere where a heat pump will be great for 90% of your winter. But for those really cold night, it won't work. Also, if this is your first heat pump, the air doesn't come out feeling warm like it does with fuel-based heats. I'm in my first force-air oil house after years of heat pumps (I keep moving more north, started in TN), and I LOVE the warm air I've never had before.
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Old 11-22-2008, 10:04 AM
 
Location: Somewhere in northern Alabama
11,490 posts, read 25,992,256 times
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Maybe the outside coil froze up? If so, the repairman may not arrive until the problem is gone.
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Old 11-22-2008, 10:29 AM
 
Location: Mesa, Az
21,157 posts, read 25,980,705 times
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Quote:
Originally Posted by rubytue View Post
Heat pumps don't work well when the outside air temp is below 35-ish. They are fairly efficient above 35, but terrible below and it will have to turn to a secondary system of some sort. This is why you hardly see any heat pumps in northern climates (north of Virginia on the east coast).

Tennessee (assuming you aren't in the top of the mountains of East TN - think Seivierville not Knoxville or Maryville) is somewhere where a heat pump will be great for 90% of your winter. But for those really cold night, it won't work. Also, if this is your first heat pump, the air doesn't come out feeling warm like it does with fuel-based heats. I'm in my first force-air oil house after years of heat pumps (I keep moving more north, started in TN), and I LOVE the warm air I've never had before.
No joke there: I am from the Wash DC area (with its surprisingly cold winters) and living here in the Phx area heat pumps work quite well.
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Old 11-22-2008, 11:11 AM
 
Location: West, Southwest, East & Northeast
3,446 posts, read 4,613,281 times
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Quote:
Originally Posted by 46Barb View Post
Our builder put in a brand new heat pump for us this summer which was great cooling this summer, but this cold is too much.

It got down to 15 degrees and we noticed the house was getting colder by the hour. The heat pump is now in alternate emergency heat trying to warm up the house. We put the temp at 65 to sleep but it got down to 60 and the alternate heat came on. It's now up to 61/62 and is trying to get warmer.

Does anyone else with a heat pump have the same problem heating when the temp outside gets into the teens here?

Now I really feel like I didn't leave the north.
Heat pumps become less efficient as the outside temperature drops. Living in TN you most certainly [should] have electric "heat strips" mounted in your air handler unit as a supplemental or backup heat source when the heat pump itself is unable to provide enough heat on its own due to low outside temperatures.

Assuming you do indeed have supplemental (backup) heat strips it sounds like you could have one of three problems. (1) the thermostats that control "when" these heat strips are energized may not be set correctly. (Note: multiple heat strips come on in stages determined by their individual thermostat settings. Heat strip thermostats are different from your wall mount thermostat inside the house.) (2) You do not have enough heat strips (enough heat strip wattage) to heat your house when temperatures dip below a certain figure in which the heat pump alone cannot provide enough heat, which is calculated based on the lowest expected temperature for your locale, factors like wind and heat loss factors associated with your particular house, e.g. windows, insulation, tightness of construction, etc. (3) The circuit breakers for the heat strips may have been turned off when the new heat pump was being installed or during servicing and were never turned back on again.
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Old 11-23-2008, 06:32 AM
 
Location: Tennessee
1,339 posts, read 2,504,479 times
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Thank you all for your advice. Yes, the temps were down to 15 for 2 days. Today it only got down to the high 20's and the heat pump worked perfectly. I lived most of my life until last year in the northeast and was used to oil/hot water heat. Oh, those warm radiators were sonice when you had cold hands.
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Old 11-23-2008, 07:07 AM
 
13,544 posts, read 22,420,220 times
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If it is a 'new' heat pump, it should be covered by manufacture warranty. Even though the builder warranty is no longer valid anytime you replace it that is a new warranty. I would call them and get the name of someone in your area to check it out.

Be sure your filter is not dirty..

I have an older heat pump and when it gets down into the low teens here in N. AL I have turned on the alternate heat once just long enough to warm up the house. I sure wish the air coming out of the vents felt warm rather than cool. Guess I am spoiled because I have a gas fireplace in the living room but I turn that off at night.
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Old 11-23-2008, 07:20 AM
 
Location: Knoxville
3,293 posts, read 10,411,264 times
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Many others have covered your problem very well. I may repeat info, but may added something too.
Regular heat pump works fine down to 32 degrees.
Between 32 and Zero, heat strips will kick in (or should)
Below Zero - it's ALL heat strips.

Keep in mind that during normal heat pump mode, the air coming out of the registers is only about 90 degrees. Feels cool to your skin, but it's still 90 degrees.

Could things could be going on.
The refrigerant charge may be "off". While you may notice some ice on the unit during operation, it will usually disappear when the unit goes into defrost mode. You will usually hear a distinct sound when it goes into this mode, and the air coming out of the registers turns cold for a few minutes while the unit defrosts. This is normal.
However, the outside unit, should not turn into a block of ice, or have a lot of ice form on the copper pipes that run into the outside unit. (If yours is not a split system ((one inside units and one outside unit)) none of this will be visible to you).
It also could be they did not install a large enough heat strip in your unit. Many heat pumps do not come form the factory with heat strips, some come with a minimum 5K. The heat strips are usually added in the field based on what the installed thinks is needed. IN your case, they may have installed a 5K heat strip, and it needs a 10K or 15K.
Think of it as trying to heat a large pot of water on the stove, but you are using the small stove element. It will heat the water up, but will take much more time than if you used the large stove element.
You may want to call the person that installed the last system and have it checked out.
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