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  1. #1

    compressor cutting out

    I went to a job today to diagnose intermittent cooling...........
    I get there to find a dirty condensor and evaporator was ok
    clean both
    turn unit on and it starts to cool
    this is what i get:
    supply air temp 68
    indoor db 79
    indoor wb 71
    outdoor db 91
    liquid line temp 163
    suction line temp 71
    hi side 277
    lo side 78
    comp amps were low @ 3-4
    resistance on compessor windings were 4, 4, 1.7
    compressor is cutting in and out
    checked voltage to compressor 118 @ each leg while running and while cutting out
    17 year old gas package unit
    3 ton r22 unit

    what could cause the compressor to cut in and out

    i feel like the compressor is bad but would think that the pressures would be different from what I got
    also with a 163 line temp I am wondering about a restriction but again wouldn't the pressures show something different than what i got

  2. #2
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,689
    your winding ohm readings are not right, they should add up, say 1, 2 , 3. not 4 , 4 ,1.5. 163 degree liquid temp or discharge? liquid thats way high you still have clogged coil. the intermitant comp shut down may be the IOL opening due to high condenser temp, would explain the wierd ohm reading. I would cool compressor to ambuent or below and re ohm.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  3. #3
    Join Date
    Oct 2008
    Location
    Nashville ,TN
    Posts
    334
    Is it split coil? Split and clean if so.

  4. #4
    Join Date
    Jun 2011
    Location
    Houston area
    Posts
    1,493
    Quote Originally Posted by Southern Mech View Post
    ......would explain the wierd ohm reading......
    How so?
    The picture in my avatar is of the Houston Ship Channel and was taken from my backyard. I like to sit outside and slap mosquitos while watching countless supertankers, barges and cargo ships of every shape and size carry all sorts of deadly toxins to and fro. It's really beautiful at times.....just don't eat the three eyed fish....

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    LMAOSHMSFOAIDMT

  5. #5
    Join Date
    Jun 2011
    Location
    Hammond,La.
    Posts
    1,176
    Are you sure your condenser fan is running at full speed? Check the MFD on fan side if you aren't sure by looking at the fan running and you know for sure the coils are clean. Or just replace with a new cap to see if there is a speed increase. Might ohm the fan motor windings as well.
    "I am for doing good to the poor, but I differ in opinion of the means. I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it."
    Benjamin Franklin, 1766

  6. #6
    Join Date
    Jul 2005
    Posts
    5,576
    Quote Originally Posted by mccutch2u View Post
    I went to a job today to diagnose intermittent cooling...........
    I get there to find a dirty condensor and evaporator was ok
    clean both
    turn unit on and it starts to cool
    this is what i get:
    supply air temp 68
    indoor db 79
    indoor wb 71
    outdoor db 91
    liquid line temp 163
    suction line temp 71
    hi side 277
    lo side 78
    comp amps were low @ 3-4
    resistance on compessor windings were 4, 4, 1.7
    compressor is cutting in and out
    checked voltage to compressor 118 @ each leg while running and while cutting out
    17 year old gas package unit
    3 ton r22 unit

    what could cause the compressor to cut in and out

    i feel like the compressor is bad but would think that the pressures would be different from what I got
    also with a 163 line temp I am wondering about a restriction but again wouldn't the pressures show something different than what i got
    I think you should try to get some more accurate measurements. A new amp/volt meter for instance. There's no way the amps were that low with those pressures. Makes me believe the winding resistances weren't measured correctly either. And 163° LL temp? Huh? The condensing temp is only 128°. The refrigerant typically cools down some before leaving the condenser coil rather than going up 35°. I think you were measuring the compressor discharge temp instead. FWIW, the low and high side pressures are about right under those conditions, as is the deltaT. Head is a little high and suction is a little low, but both could be normal depending on the SEER. SH is a bit high, but not enough to worry about.

    If it's cutting out, then you should be looking at the electrical components and connections.

  7. #7
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,689
    Quote Originally Posted by Cooked View Post
    How so?
    I am basing that on the IOL. compressor being hot and ready to open at any time.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  8. #8
    Join Date
    May 2009
    Posts
    589
    Suction line temp of 71 degrees will cause thermal cutout intermittently. If the unit is consistently running that temp back to the compressor many will overheat.

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