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  1. #1
    Join Date
    Aug 2011
    Location
    houston, texas
    Posts
    20

    thermal overload

    i learned something new today. i was checking the windings on a compresser on a ruud 5 ton condenser and i was getting open line on common and start...and common and run. i thought the compresser was bad but another tech told me to try cooling the compressor down and re-check the windings. he was right.

  2. #2
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,664
    many a compressor have been condemed for this. In the schematic drawing for the compressor you will see this O/L.

    made the same mistake many moons ago when fresh in the trade.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  3. #3
    Join Date
    Aug 2011
    Location
    houston, texas
    Posts
    20
    yep. im new to the trade and running calls by my self. so i look at everything over and over and ask other techs on the phone lots of questions.

  4. #4
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,316
    On a single phase compressor, if your open from common to start or common to run but you have normal resistance from run to start, then your overload is open. Look at the compressor wiring diagram and you'll see that the overload is in the common circuit and you'll see why you'll have continuity from run to start. In addition to cooling down the compressor, I gently tap the compressor with a hammer by the overload and sometimes it closes it.

  5. #5
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,664
    another thing to learn here is, they just don't open by themselves, find the problem.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  6. #6
    Join Date
    Aug 2011
    Location
    houston, texas
    Posts
    20
    thanks guys. yea the compressor was super hot so i went and checked the air filter and it was 100% clogged. i mean a freaking blanket. by the way where is the overload on it?

  7. #7
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,664
    Quote Originally Posted by el_coyote2373 View Post
    thanks guys. yea the compressor was super hot so i went and checked the air filter and it was 100% clogged. i mean a freaking blanket. by the way where is the overload on it?
    on A/C and H/P they are internal, hence internal overload/ IOL. on refrigeration reach ins and small ptac style, there in the terminal cap and can be replaced.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  8. #8
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    A compressor is like a body, its not dead until its cold and dead.
    Karst means cave. So, I search for caves.

  9. #9
    Join Date
    Sep 2008
    Location
    Largo
    Posts
    78
    Do a continuity test right off your contactor between the red and black/blue wire (Trane unit). If your meter doesn't beep then circuit is open (internal overload). I get out my alligator clips and hook my meter up to both wires. I hose down the compressor till my meter starts beeping showing continuity again. Put the cover back on and start it up. Just a little trick of the trade. If my schedule is backed up I will blast a compressor with liquid refrigerant to cool it off quick. Always check your run or start cap first too. normally a failed condenser fan or low refrig charge is what caused the compressor to go into internal overload. Good luck!

  10. #10
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,316
    Quote Originally Posted by MetroAir View Post
    If my schedule is backed up I will blast a compressor with liquid refrigerant to cool it off quick
    I can't believe that I'm reading a comment like this from a professional member!

  11. #11
    Join Date
    Aug 2011
    Location
    houston, texas
    Posts
    20
    yep. it is a 410a system and the pressures were 160/320. the condenser fan motor was running when i showed up and the cap was good. the only thing i found was the dirty filter.

  12. #12
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,664
    Quote Originally Posted by R123 View Post
    I can't believe that I'm reading a comment like this from a professional member!
    I know right? WTF
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  13. #13
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,316
    And he has a lot of identifying info on his profile. He may not be a Trane Comfort Specialist much longer by admitting that on the internet.

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