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  1. #1
    Join Date
    Nov 2007
    Location
    Livermore, Ca
    Posts
    163

    Heat Pump frosting vs icing

    Have been reading the owners manual for our Rheem HP and the White-Rodgers T-Stat for tidbits of info on the working of the unit(s).

    The troubleshooting part of the HP states that the outdoor condensor may have frost. It then said that if ice builds up to call the technician.

    Question is, what will cause the outdoor unit to ice?
    Clogged coils is obvious. But what else?

  2. #2
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,368
    Frost is normal for heat pumps until it defrosts. Ice can form from the system not defrosting, wrong refrigerant charge, a restriction, and other reasons.

  3. #3
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    Frost is soft and flaky, ice is hard and slippery.
    Karst means cave. So, I search for caves.

  4. #4
    Join Date
    Nov 2007
    Location
    Livermore, Ca
    Posts
    163
    It said ice is bad. There is a fine line between frost and ice.

    I did notice once last year on one of our coldest days, ice on the coils. Caught my eye as not being right.

    I'll keep the other eye on it this winter season for more history

  5. #5
    Join Date
    Mar 2003
    Posts
    1,234
    The frost is normal, of course, but ice usually indicates that there wasn't sufficient heat generated during defrost to remove all the frost. Most of the time I find the system a bit low on charge and the defrost cycle times out (10 min.) before it can remove all of the frost then when it goes back into the heating mode the frost continues to build up in the areas that did not initially defrost. This usually is why the ice builds up on the lower portion of the outdoor coil and basically restricts the airflow through that portion which results in further problems.

  6. #6
    Join Date
    Jun 2007
    Location
    The Twilight Zone
    Posts
    2,964
    Quote Originally Posted by regis101 View Post
    There is a fine line between frost and ice.
    No fine line. Frost is not ice. As stated by Karsthuntr, "frost is soft and flaky, ice is hard and slippery."

    Some heat pumps have time initiated defrost where you can choose 30, 60, or 90 minutes. Other units defrost when they sense that it is needed.

    Don't worry, be happy.

  7. #7
    Join Date
    Nov 2007
    Location
    Livermore, Ca
    Posts
    163
    Thanks. I'll check into the defrost feature.

  8. #8
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,829
    Some of the latest unit actually let the tech select the first defrost cycle only. After that, the unit records it's time to defrost to a particular unit temperature then adjusts the next defrost cycle accordingly. This pretty much guarantees against the formation of ice during the defrost cycle unless there's a mechanical problem. Then it's time to call in the tech, so.....
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  9. #9
    Join Date
    Nov 2007
    Location
    Livermore, Ca
    Posts
    163
    Thanks.
    I did have an ice episode last season. I am trying to understand if this could also be because the 3T unit is oversized for the 1129 sq ft house.

  10. #10
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,368
    I'm not a pro, but I'm pretty sure oversizing shouldn't cause icing up.

  11. #11
    Join Date
    Nov 2007
    Location
    Livermore, Ca
    Posts
    163
    We're all pro at something.

    Thanks for your input.

    I will say that for as frustrating as it has been doing a self diagnosis on this troublesome system, it has also been fun researching the nature of the Heat Pump.

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