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  1. #1
    Join Date
    Nov 2019
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    Run Side of Compressor Issue

    Hello,

    My outdoor 12 year old Trane heat pump / compressor is having an issue. The unit is getting power and the fan runs properly. But, when the compressor fires up, it runs for about 5 seconds, then stops, while the fan continues to run. This pattern repeats every 60 seconds or so.

    I had an HVAC tech come out. He checked the following:

    • Capacitor - OK, read 50/5 as per marked on can
    • Checked voltage into system - OK
    • Checked refrigerant pressures - OK
    • Bypassed Hard Start - no change
    • Manually actuated the Reversing Valve - Functioning OK
    • Ohmed out compressor - OK
    • Checked voltage at reversing valve - OK
    • Compressor is rated for 88 max start up amps. It was pulling around 84 start up amps, then leveling out to normal levels


    His conclusion was that the "run side of compressor is not allowing system to run."

    What are your thoughts? Does that sound like a bad compressor that is unrepairable?

    If the compressor IS bad, and with R22 getting more expensive, would you advise biting the bullet and updating the system to a new modern system. Or is there a less expensive avenue to get me back up and running?

    --Thanks

  2. #2
    Join Date
    Jul 2011
    Location
    DFW, TX.
    Posts
    1,481
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    Sorry to say but you just need a better tech. Its hard to find experienced techs in residential these days. Call around tell them your issue and say you'll pay for the diagnostic fee and go from there... Hopefully its something simple.

    Sent from my LG-G710 using Tapatalk

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    40,576
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    If the compressor dropped from start to "normal levels" sounds like it IS running & pumping. Unless he meant dropped to 0 amps after trying to start. Then it's locked up.

  4. #4
    Join Date
    Nov 2019
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    Thread Starter
    Sorry, I should have clarified. The compressor starts, pulling 80+ amps at start for less than 1 second. The amps immediately reduce to correct values for about 5 seconds. Then the compressor fails to 0 amps and stops running.

    Thanks.

  5. #5
    Join Date
    Nov 2019
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    Thread Starter
    Here is a short video of the issue.

    youtu.be / jXBePbe20Ds

  6. #6
    Join Date
    Oct 2016
    Location
    Clearwater, Florida
    Posts
    1,557
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    IF the compressor actually runs, which it would have to for pressures to be "OK" then the compressor is probably not the issue.

    there's normally an internal safety in the compressor that protects it from running if it gets too hot. Compressors rely on the refrigerant cooling them so if there is not enough refrigerant or a restriction, it can cause it to overheat. Some systems also have high and or low pressure cut off switches to protect the system in either case.

    BUT, the real question is, does the compressor actually RUN or just humm and then cut off.

  7. Likes CEAS-AC-TECH liked this post.
  8. #7
    Join Date
    Nov 2019
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    Thread Starter
    Thanks for your reply! It seems to me that it is actually running for about 5 seconds, then failing. Here is a video of it I just took.

    youtu.be/jXBePbe20Ds

  9. #8
    Join Date
    Oct 2016
    Location
    Clearwater, Florida
    Posts
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    Okay, I can't see the video but that's fine.

    Who said the pressures were "OK"?

  10. Likes CEAS-AC-TECH liked this post.
  11. #9
    Join Date
    Nov 2019
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    Thread Starter
    The tech attached his pressure gauges and indicated they were appropriate for my system. I cant remember exactly what he said the measurements were, sorry.

  12. #10
    Join Date
    Oct 2016
    Location
    Clearwater, Florida
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    If the compressor didn't run then there's no way he could verify that. Getting pressures and seeing if they are good or bad takes at least a couple of minutes of run time.

    He may have looked at the system when it was off and seen equal pressure on both sides and assumed it was fine, but that's not a valid way to check it. If the system is low it could be running into a vacuum right when it starts at which point, if it has a low pressure switch, it will kill the system.

  13. #11
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
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    Quote Originally Posted by ntx_homeowner View Post
    The tech attached his pressure gauges and indicated they were appropriate for my system. I cant remember exactly what he said the measurements were, sorry.
    I’ll get in trouble for the second time today


    BS!

  14. #12
    Join Date
    Sep 2008
    Location
    VA
    Posts
    3,725
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    It’s hard to say without personally testing it.
    May be a bad compressor, or maybe the capacitor is wired backwards to the compressor.
    There are no high voltage limit controls to the compressor with exception of the internal over load. Typically the IOL will take several minutes to an hour to reset. That’s not to say you don’t have a bad IOL. I’ve seen this happen with a stuck pot relay, but you said the tech bypassed the start cap. Maybe the pot relay and, or start cap is bad. Most compressors can start without its start cap, but some can’t. So, I don’t really have firm answer without personally testing.

    Can’t really go much deeper without infringing upon the NO DIY rules.
    "The only true wisdom is in knowing you know nothing" Socrates

  15. #13
    Join Date
    Oct 2016
    Location
    Clearwater, Florida
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    Quote Originally Posted by pecmsg View Post
    I’ll get in trouble for the second time today


    BS!

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