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  1. #27
    Join Date
    Apr 2001
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    Quote Originally Posted by davefr View Post
    It sounds like another case of randomly throwing parts at the situation without taking the time to get down to root cause.

    Oh come on! Nowadays, who the hells got the required 10,000 hours to properly train an HVAC service technician? Give the guy a break! Self training in the HVAC service industry is the new norm today....or haven't you figured that out yet?



    Jabs

  2. #28
    Join Date
    Jan 2004
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    PA
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    68,770
    Not allowed to go into more detail in the resi forum.

    Think what else can be pulled at the indoor coil.
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    How many times must one fix something before it is fixed?

  3. #29
    Join Date
    Jul 2007
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    12
    Quote Originally Posted by beenthere View Post
    Not allowed to go into more detail in the resi forum.

    Think what else can be pulled at the indoor coil.
    Email me at

    Why cant you express your opinion???

    What else can be pulled at the E.coil other than making sure it is clean, and ensuring an unclogged orifice?
    Last edited by beenthere; 07-13-2009 at 06:59 AM. Reason: Removed email address

  4. #30
    Join Date
    Jul 2007
    Posts
    12
    Just re-found this thread.

    So... it ended up being my compressor. I toughed it out another summer... with it working randomly.

    Essentially, the compressor was always running.... but sometimes it would not build up enough pressure to compress the freon adequately. Sometimes it would. Even when it would - the high side pressure never got to as high as it should be.

    Replaced the outside unit with a 14 SEER, and my AC guy installed a TXV on the existing coil to increase the efficiency... working great ever since, and I see a 10 to 15% reduction on electricity KWH in the summer.

  5. #31
    Join Date
    Apr 2009
    Location
    Texas
    Posts
    243
    I've seen this happen on some units when scroll compressors first became popular: If the unit short cycles, the scroll compressor can run backwards. Everything sounds the same because the fan and comp. are both running - once your tech puts his gauges on the unit he should be able to tell if this is happening. Question: when the unit works well, is it after it has been off for 20 - 30 minutes and then comes on?

  6. #32
    Join Date
    Jul 2007
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    12
    Quote Originally Posted by gasser65 View Post
    I've seen this happen on some units when scroll compressors first became popular: If the unit short cycles, the scroll compressor can run backwards. Everything sounds the same because the fan and comp. are both running - once your tech puts his gauges on the unit he should be able to tell if this is happening. Question: when the unit works well, is it after it has been off for 20 - 30 minutes and then comes on?
    Yes. It would cycle on and off in normal cycles, and work great, usually 15-30 minutes between cycles.... then cycle on and just not cool. That cycle would never end because the house just slowly warmed up on that cycle.

    However, I am not sure if it was running backwards.... because there was some compression/cooling during that time. There was a bit of cooling ocurring, because there was a 5-10 degree drop over ambient temperature between the filter intake, and the register output. Unless running backwards can do that....

  7. #33
    Join Date
    Apr 2009
    Location
    Texas
    Posts
    243
    I think you really need to get the tech there while the unit is doing what you describe. This is not too hard to diagnose, but you have to catch it at the right time. Good luck!

  8. #34
    Join Date
    Jul 2007
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    12
    Quote Originally Posted by gasser65 View Post
    I think you really need to get the tech there while the unit is doing what you describe. This is not too hard to diagnose, but you have to catch it at the right time. Good luck!
    As I posted - this is resolved. I just came back to update the solution.... it was a bad compressor.

  9. #35
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    "Bad" compressor doen't define the nature of the failure. Here is how it can happen:

    The compressors have a high pressure relief valve inside. Under some conditions, the valve may popoff and the compressor continue to run doing very little cooling. The next time the compressor stops for some reason, the valve will reset and the compressor will operate normally until conditions cause the valve to popoff again. Overcharging a system can cause this to happen, and repeated popping off can weaken the releif valve to the point of popping off under heavy but normal conditions.

    Your symptoms match this behavior perfectly.
    Glad you got it fixed.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  10. #36
    Join Date
    Jun 2005
    Location
    SW Wisconsin
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    Quote Originally Posted by lynn comstock View Post
    "Bad" compressor doesn’t define the nature of the failure. Here is how it can happen: The compressors have a high pressure relief valve inside. Under some conditions, the valve may popoff and the compressor continue to run doing very little cooling. The next time the compressor stops for some reason, the valve will reset and the compressor will operate normally until conditions cause the valve to popoff again. Overcharging a system can cause this to happen, and repeated popping off can weaken the releif valve to the point of popping off under heavy but normal conditions. Your symptoms match this behavior perfectly. Glad you got it fixed.
    Just noticed this thread.

    My experience has been that a compressor internally bypassing has a very distinctive louder noise that is easily detected, verses a normal operating compressor.

    Therefore, you should listen to the compressor when it is operating while cooling normally, then listen to it when not cooling, note any difference & if different, report that to a Tech.

    The compressor's internal by-pass can also be triggered by too great a pressure differential between the high-side & low-side.

    When the new condenser was installed, they put a TXV metering device on the evaporator coil.

    Therefore if something were intermittently plugging the piston orifice hole it won't cool, or the orifice piston was occasionally sticking, therefore not seating, refrigerant would bypass it the same as if it were installed backward, which I have found on a few occasions.

    That is the equivalent of a compressor bypassing.
    Therefore, the compressor may not have been the problem.
    - Darrell
    Last edited by udarrell; 07-16-2009 at 10:10 AM. Reason: -plugging the piston orifice hole it won't cool,

  11. #37
    Join Date
    Jul 2007
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    12
    Quote Originally Posted by udarrell View Post
    J

    Therefore if something were intermittently plugging the piston orifice hole it won't cool, or the orifice piston was occasionally sticking, therefore not seating, refrigerant would bypass it the same as if it were installed backward, which I have found on a few occasions.

    That is the equivalent of a compressor bypassing.
    Therefore, the compressor may not have been the problem.
    - Darrell
    That sounds reasonable. However, when the tech noticed that low high side pressure, he closed the high side valve with the gauges on, and watched the pressure not able to build. The compressor was not able to bring the refrigerent into the condensor, or bring the pressure up at all, even with the high side valve closed, which is why he diagnosed the compressor being bad.

    Does that make sense?

  12. #38
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    Jun 2005
    Location
    SW Wisconsin
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    Quote Originally Posted by igotdoo View Post
    That sounds reasonable. However, when the tech noticed that low high side pressure, he closed the high side valve with the gauges on, and watched the pressure not able to build. The compressor was not able to bring the refrigerent into the condensor, or bring the pressure up at all, even with the high side valve closed, which is why he diagnosed the compressor being bad. (Ha..., I wonder Why...)

    Does that make sense?
    If the refrigerant flow is nearly completely blocked at the orifice, the high-side pressure won't increase because there will be scant little vapor for it to pump into the condenser, which would immediately condense leaving near an ambient pressure.

    Barring any non-condensibles, etc., the vapor in the condenser will all condense into liquid showing R-22 pressures at near the outdoor temp.

    What was the temp outside at the condenser, & what was the pressure/temp reading on the gauge...?


    That situation would not increase the pressure, as that is the way we pump the system's refrigerant down into the condenser, I usually sprayed a little cold-soft-water on the condenser while the compressor pumped it down, or nearly down.

    It is not a good idea to let the low suction side pull into a deep vacuum, as we used to do to check compressors', several negative things could occur, which I will not mention here. - Darrell
    Last edited by udarrell; 07-16-2009 at 01:54 PM. Reason: deep vacuum - as we used to do to check compressors'

  13. #39
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    Jul 2002
    Location
    Yuma, AZ
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    No way to be certain

    Quote Originally Posted by udarrell View Post
    My experience has been that a compressor internally bypassing has a very distinctive louder noise that is easily detected, verses a normal operating compressor.
    Usually, but I have been surprised more than once by near normal sound.

    Therefore, you should listen to the compressor when it is operating while cooling normally, then listen to it when not cooling, note any difference & if different, report that to a Tech.
    If you are lucky enough to have it running and not cooling well, when you stop the compressor, if the pop off was bypassing, there will be a hissing sound briefly followed by a distinctive "click" when the valve resets.

    When the new condenser was installed, they put a TXV metering device on the evaporator coil.

    Therefore if something were intermittently plugging the piston orifice hole it won't cool,
    In this case it would soon shut down on compressor overheat and stop cooling completely...

    or the orifice piston was occasionally sticking, therefore not seating, refrigerant would bypass it the same as if it were installed backward, which I have found on a few occasions.

    That is the equivalent of a compressor bypassing.
    Therefore, the compressor may not have been the problem.
    Excellent alternate possibility that would allow the compressor to keep running and producing a higher coil temperature and the basic symptoms reported.
    However, what would make the piston move out of the seated position where the refrigerant flows through the orifice? Gravity? Possibly but that would mean that the piston slides easily.

    Bottom line is that we cannot prove either possibility remotely. But considering these possibilities while the tech is on the job to test them one way or another is the way a professional thinks. Good Job.

    Lynn
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

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