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-   -   Heat pumps in cold weather (https://www.askmehelpdesk.com/showthread.php?t=438975)

  • Jan 25, 2010, 10:19 AM
    catwoman57
    Heat pumps in cold weather
    I have never had a heat pump before so am not sure what the problem is, first of all it was coated with a white substance for quite awhile. The top of it was free of stuff, fan running etc. The top foot or so on the side woul come off if you scraped it off the bottom white stuff was more like ice. When the heat pump is turned off the white stuff goes away when turned back on it comes back.
    The problem I am having now is that the thermastat was set for 68 degrees, the green light comes on as you know and it is supposed to run until the temp gets to the temp you want. The green light came on and stayed on and never went off, cold air was coming up out of vents but not HOT. I live in Oregon and it has been mid 40's during the day.
    Its like it is trying toget up to that temp but never makes it. I am using emerency heat now Hot aire comes up the vents which I want but have heard that it costs more to run it that way. I am hearing impaired so cannot hear it, any noise it makes.
    Thanks.
    Kristeen G
  • Jan 25, 2010, 10:26 AM
    hvac1000
    You just described the normal cycle for a heat pump.


    HowStuffWorks "How Heat Pumps Work"

    Learn How Your Heat Pump Works

    YouTube - How a Heat Pump Works

    Heat Pumps - How Well Do They Work?
  • Jan 25, 2010, 05:57 PM
    Justin Orr

    The white stuff is frost and is normal. With heat pumps, they stop producing enough heat when the outside temp reaches the high to mid 30's, which is why auxiliary (also called emergency) heat is used. As long as your emergency heat works, everything seems to be working normally and you'll be okay.
  • Feb 7, 2012, 07:14 AM
    wjmeier
    Heat pump effectiveness depends on the local utility costs, local climate, system controls and installation. I have owned several homes with heat pumps. The unit with my last home had poor defrost logic and was located in a very humid climate. That unit became a block of ice when it was cold outside. Because my backup heat was natural gas I did not use the heat pump in the winter with that unit. I would have an HVAC professional look at your unit to see if the defrost logic can be improved.

    You should be aware a heat pump will not put out air as warm as other heating systems. Mine runs about 95 F at the register outlet.

    My current unit is a Ruud heat pump with demand defrost logic. This works much better than the older Trane unit that I had in the past. I was also able to adjust the demand logic to use even less electricity, but still defrost the unit well.

    My current home is all electric and natural gas is not available in this market. I live in central Missouri. My home is 3300 sq. ft. and currently uses a maximum of 2200 KWh a month in the winter.

    I was able to improve the system performance as originally installed by 35% by doing the following. The reason this was possible is that the system did not manage the backup electrical strip heat well. I added an outside temperature sensor and replaced the White and Rodgers thermostat with a Honeywell IAQ thermostat. The Honeywell unit is much better at managing the strip heat and maintaining a more even temperature in the home. I have set my system to run no more than twice an hour to prevent the heat pump from cycling on and off and not operating as efficiently. I also determined my system will operate well to 5 F outside temperature. The compressor will not operate below -5 F because of a low pressure limit on the compressor. I have set the thermostat to allow the heat pump to run from 5 F and higher. The strip heat is locked out at 35 F and higher.

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