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  1. #1

    heat pump screeched in the cold - compressor shot?

    Our 1000 sq ft condo is heated and cooled by a 1.5 ton heat pump.
    It's an American Standard Heritage unit, about 20 years old.

    In Boston's cold winter this year, the outdoor unit started to make a screeching sound, usually when it had just started to run, or maybe when it was shutting down. It produced heat just fine, although our bills seemed somewhat higher than normal.

    As Murphy's law would have it, it stopped screeching earlier in the week (maybe because of warmer temperatures?) but we couldn't get a heating guy in until today.

    The fan runs smoothly without screeching. So the technician tells me that the problem must be in the compressor, and that the compressor will need to be replaced.

    Does that sound accurate? Any chance this is fixable without changing the whole compressor? Money is tight and we are not planning to live here more than four more years.

  2. #2
    Join Date
    Sep 2006
    Location
    Montana
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    983
    If the compressor is bad, it would be foolish to replace it in a 20 year old unit. Your money would be better spent investing in a new system. The compressor in your system is a sealed unit, which means there is no way to open it up and rebuild it. If it's bad, it would need to be replaced. My advice would be to replace the system. Yes, it's going to cost you some money, but it's going to be more efficient than the system you have now. At 20 years of age, it's really hard for me to justify replacing the compressor, you'd be throwing good money away.

  3. #3
    Join Date
    Jul 2010
    Location
    nebraska
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    More then one thing could cause the screeching sound and of the possibilites are going to cost way more then you should put into a 20 year old heat pump. Replace it now or wait untill it dies but don't put serious money in that unit.

  4. #4
    The condo was my wife's before we recently got married.
    She tells me the screeching sound has always been there in the winter, but this year was much worse.

    Interestingly, the screeching seems to happen on a schedule, every 20 minutes when it is cold. Today was warm and it did not screech at all.

    Does this shed any light on what is causing the screeching, and whether it means that the compressor is really shot?
    .

  5. #5
    Join Date
    Sep 2006
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    Montana
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    Quote Originally Posted by MikeInMass View Post
    The condo was my wife's before we recently got married.
    She tells me the screeching sound has always been there in the winter, but this year was much worse.

    Interestingly, the screeching seems to happen on a schedule, every 20 minutes when it is cold. Today was warm and it did not screech at all.

    Does this shed any light on what is causing the screeching, and whether it means that the compressor is really shot?
    .
    It's too hard to accurately tell from here. Being on site and able to see/hear it would be the only way to diagnose it. If the compressor doesn't run, there are few things that can be eliminated. If after those tests/checks the compressor still doesn't run, then it probably is shot. If you don't trust the first tech, call a different company and get a second opinion.

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    33,901
    Could be a defrost though 20 minute intervals on a demand defrost unit seem weird.

  7. #7
    Quote Originally Posted by big sky hvac View Post
    If after those tests/checks the compressor still doesn't run, then it probably is shot.
    The compressor runs and produces heat just fine, it's just that it screeches every 20 minutes in the cold.

  8. #8
    Join Date
    Jun 2009
    Location
    South Jersey
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    30
    Did the tech hear the screeching sound or was he just going off of your word?

  9. #9
    It didn't screech today (it's a warm day), so the tech was just going off my word. I hate to replace the whole heating system without a pro actually hearing the noise. It is pretty loud though.

  10. #10
    Join Date
    Jul 2010
    Location
    georgia
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    562
    Videotape it when it's screeching. Maybe it would be useful in a diagnosis.

  11. #11
    Join Date
    Jun 2009
    Location
    South Jersey
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    30
    There's another component inside a heat pump with moving parts besides the compressor and the fan that tend to make a bit of an annoying sound at start up or shut down. Without actually hearing the sound for myself (and your tech for that matter) you can't really condemn the compressor - they are just too damn expensive to replace on a hunch. Especially if the unit has always made this noise according to your wife, not to mention you say it heats and cools just fine. I'm not saying your tech isn't correct in his diagnosis, just that there MIGHT not be anything seriously wrong

  12. #12
    Join Date
    Jun 2005
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    SW Wisconsin
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    Quote Originally Posted by MikeInMass View Post
    The compressor runs and produces heat just fine, it's just that it screeches every 20 minutes in the cold.
    So, it only screeches in the heating mode in cold weather.

    The system may not be maintaining the 75+ to 100-psig differential pressure between the suction side & the head pressure side, - to hold the reversing valve in position.

    Does it cycle the reversing valve in the heating mode?
    If not; that would not be a cause of the screeching.

    The compressor could have a weak internal bypass, that bypasses & then somehow resets. When by-passing, it makes a loud noise.

    I'd find where & what is causing the screeching & fix it; at this point - I would not replace the compressor or condenser.
    Outdoor fan motors can screech at odd intervals.
    Last edited by udarrell; 04-15-2011 at 05:37 PM. Reason: Explanation

  13. #13
    Quote Originally Posted by udarrell View Post
    Does the it cycle the reversing valve in the heating mode?
    Unfortunately, I have no idea how I'd even begin to answer this question. Heat pumps are totally new to me.

    Videotaping the screeching, and asking another tech, both seem like good ideas.

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