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  1. #1
    Join Date
    Sep 2011
    Posts
    85

    Low head, normal suction, HIGH amps

    5 ton scroll compressor in a split system.

    Suction ~40psig
    Discharge ~210psig
    Amps 30+A
    Superheat ~17

    It is a 3 phase compressor, pulls 30 amps from the get go and will go all the way to 40 amps (and shut off)

    The winding(s) resistance is about .5 ohms on all of them. It also doesnt sound great when it is running. I recovered 20 pounds of refrigerant from this system, recharged with around 7.5 pounds... After cleaning the ridiculously dirty evaporator.

    Just looking for affirmation, thank you for your input.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,928
    7.5 pounds sounds low on a 5 ton split system.
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  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,574
    Quote Originally Posted by wdshea View Post
    5 ton scroll compressor in a split system.

    Suction ~40psig
    Discharge ~210psig
    Amps 30+A
    Superheat ~17

    It is a 3 phase compressor, pulls 30 amps from the get go and will go all the way to 40 amps (and shut off)

    The winding(s) resistance is about .5 ohms on all of them. It also doesnt sound great when it is running. I recovered 20 pounds of refrigerant from this system, recharged with around 7.5 pounds... After cleaning the ridiculously dirty evaporator.

    Just looking for affirmation, thank you for your input.
    Did you measure amps on all 3 legs?

  4. #4
    Join Date
    Apr 2007
    Location
    T.C minnesota
    Posts
    12
    I'm guessing R-22. If so looks like low suction, normal head. more info would help. I like to megaohm the compressor to ensure the windings are good.

  5. #5
    Join Date
    Oct 2001
    Posts
    6,966
    split unit what was the ambient around the condenser 210PSI air cooled is low for R-22.how is the condenser on being clean...flush it inside out.... is this a commercial site strip mall or residence?
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  6. #6
    Join Date
    Sep 2011
    Posts
    85
    Im sorry, i was thinking of my suction saturation when i said 40, pressure was around 69psig on the suction. Yes i checked all three legs. I cleaned the condenser twice. This is commercial.

    Megaohm the windings to ground?

  7. #7
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    You can use a megger if you have one. Isolate the leads from the compressor and megg from the compressor terminals to ground.

  8. #8
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,574
    typically, a short to ground is not going to cause high running amperage.

    That would be more likely to cause high instantaneous amperage and result in a breaker trip.

    I would leave the megger in the truck here.

    I'd look for a performance curve on that pump and see what the manufacturer says that it SHOULD draw under those conditions.

    I suspect that you'll be replacing a compressor, soon, though.

  9. #9
    Join Date
    Sep 2011
    Posts
    85
    The olp trips pretty quick, it never pulls less than 30 amps, so it only runs about 5 minutes, if that. I thought that maybe a previous tech may have the motor running backwards, so i switched some leads. AmP draw went to 12A but the compressor sounded like hell, so i'm certain it was running the right way.

  10. #10
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,574
    Quote Originally Posted by wdshea View Post
    The olp trips pretty quick, it never pulls less than 30 amps, so it only runs about 5 minutes, if that. I thought that maybe a previous tech may have the motor running backwards, so i switched some leads. AmP draw went to 12A but the compressor sounded like hell, so i'm certain it was running the right way.
    A grounded winding will typically pop the breaker/overload instantly, not over a couple of minutes.

  11. #11
    Join Date
    Sep 2011
    Posts
    85
    What else could this be? I was thinking shorted windings

  12. #12
    Join Date
    Jul 2012
    Location
    Dillwyn, VA
    Posts
    43
    What is the LRA and what is the compressor rated at? 30 plus amps sounds high in a 5 ton system.

  13. #13
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,383
    My guess would be the bearing are going bye bye. 30 amps on a 5 ton 3 phase compressor? Not long for this world!
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