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  1. #1
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    Compressor Windings



    I have a 22 kW Mitsubishi Electric condensing unit with a 10HP Mitsubishi compressor that comes up with U6 error code. A U6 error code is over current.
    The compressor is a 3 phase compressor with a maximum running current of 22 Amps.
    I test the compressor for the following:
    Phase to phase resistance of all windings is 17 Ohms
    Insulation resistance of all windings is 0 Megohms.
    The compressor runs for about 1.0 to 1.5 seconds then comes up with the U6 error code.
    Does any one know what the compressor winding should be for a Mitsubishi Electric compressor model # JH521YEB?
    I have been told around the 1.0 Ohm or so.
    If the compressor windings have increased in resistance, how is this so?
    After talking to Mitsubishi I have found that a U6 error occurs from one of 2 inputs:
    The thermal overload NC contacts or the compressor thermostat, NC contacts which are in series.
    I have disconnected both of these and bridged the CN23 pins on the outdoor circuit board and the outdoor unit comes up with a H7 code then trips the circuit breaker when started.
    I have tested the contactor - Perfect
    I have tested the the thermal overload - Perfect
    I plugged in CN23 connector after this test and I get H2 & H6 code.
    As the compressor is not down to earth or not jammed, can anyone of you giys come up with what is going on?
    This one is a first for me, 40 years of doing this!



  2. #2
    Join Date
    Oct 2001
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    Nottingham UK
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    Re: Compressor Windings

    Quote Originally Posted by petem View Post

    Insulation resistance of all windings is 0 Megohms.
    Winding resistance to Ground (Earth) should be very high when measured using a Meggerohm meter.

    A reading of 0 Megohms indicates a direct short

  3. #3
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    Re: Compressor Windings

    Sorry, I wrote that down wrong, resistance is high, no leakage to earth

  4. #4
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    Re: Compressor Windings

    If you disconnect the compressor from the circuit does the unit still trip on overcurrent?

  5. #5
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    Dec 2012
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    Re: Compressor Windings

    No,
    As I said, the windings are not down to earth using a megger at 1000V and resistance between all three windings is 17 ohms.

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