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Thread: HVAC Question

  1. #1
    Join Date
    Dec 2006
    Location
    Herndon VA
    Posts
    180

    HVAC Question

    OK this will probably be a dumb question, but here goes......

    I have a 2 zone HVAC system. One of the outside heat pump units runs pretty cold. So cold that after today's rain, the top has frozen chunks of ice around the fan shroud. The second unit that sits right next to it and is also a Carrier, is perfectly fine. The one with ice controls the main level of the house and tends to run longer.

    Is this normal?

  2. #2
    Join Date
    May 2007
    Location
    Kansas City, Missouri
    Posts
    13,443
    I'm not an expert, but it sounds like it is low on freon, which will usually cause it to freeze over. What is the outside temperature? I know mine will switch to gas heat when it gets below 35 outside.
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  3. #3
    Join Date
    Dec 2006
    Location
    Herndon VA
    Posts
    180
    It is in the upper 30's. Both units are only 4 years old. I was told by the installer (friend of the family) that annual service was not required until about 5 years old. I guess it's time...

  4. #4
    Join Date
    May 2007
    Location
    Kansas City, Missouri
    Posts
    13,443
    Have you washed the coils on them lately? I've got a neighbor with a cottonwood tree and have to wash the cotton out mine several times a season or it will clog up the coils. Just need to take a hose outside with a sprayer and wash them down top to bottom on each side. Might flip off the breaker to them first. But could be the problem, but still sounds a bit like low freon.
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  5. #5
    Join Date
    Jan 2007
    Location
    Trinity County - 160 miles north of San Francisco. Redwood forest.
    Posts
    159
    When we built our new home in the mountains of Northern California I selected a heat pump. Having studied about heating/ac for our old home (boiler and radiant panels in 4 zones), I knew enough to choose the latest technology known as 2-stage heat pumps. I'd heard that older versions can't produce heat at much less than mid-30s temps.

    One recent night, the pump was operating in 17 degree weather w/o the heat strips taking over. the 2-stage device is supposed to save about 40% on both heating and cooling. I bring this up because, if you have the option to replace the pump unit, get a 2-stage.

    Gary Curtis
    Trinity County Calif

  6. #6
    Join Date
    Dec 2006
    Location
    Herndon VA
    Posts
    180
    Well after making the cardinal man-sin.... I consulted the manual!

    It says the ice build up on the unit is normal in colder temps. Either way I guess I'll start getting an annual service.

  7. #7
    Join Date
    Oct 2006
    Location
    The Heart of Dixie
    Posts
    4,268
    Everyone has an opinion but after what I have seen as a Home Inspector I suggest annual service to my clients. Cleaning the coils is the biggest part of that too. As the coils get dirty, the efficiency of the unit drops. It will still cool and heat the house, just costs you more money to operate it.

    My HVAC buddy tells me that the minimum temperature difference between Return air and Supply air should be 12 degrees. At that point he says your well past the point your should have serviced the unit. It's still working but it's costing you more to operate it. I would say well over 50% of the units I check are at the 12 or 13 degrees difference.

    Where you live and what is around you will have an effect on how fast your coils clog up too. I just have him come out each spring and take care of mine.
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


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