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  1. #14
    Join Date
    Nov 2003
    Location
    Montreal, Qc.
    Posts
    780
    Before condeming any semi hermetic due to a suspected short circuit I remove the terminal plate and disconnect the wires to test the windings with a megger.
    The service valves must be front seated and the refrigerant recovered from the crankcase prior to removing the terminal plate.

    Carlyle Service Guide

    From the Thermacon Compressor Guide

    Compressor Testing Guide
    Please use this guide if you suspect a faulty compressor
    To verify basic compressor function in a field environment the following will
    demonstrate whether further investigation will be necessary or not.
    1 Earth Test Using a 1000v Megger check each field winding
    to earth. 1st check the earth connection is
    sound by an earth to earth test & repeat this
    following the motor test.

    If reading < than 2 M Stator probably burnt out,
    but do not rule out a contaminated / damp
    terminal plate.

    Reading 2 M - 20 M Probably not burnt out, terminal plate
    contaminated or damp.
    Separate terminal plate from main casting &
    repeat check to casting. If fault clears then
    terminal plate is faulty.

    Reading > 20 M No earth Fault

    Precautions Do not effect Megger checks under deep vacuum.
    Do not Megger overloads.

    2 Field Balance Using an Ohmmeter set on Ohms verify balance
    3 motors only of motor field coils.
    If balance is out by more than 10 % suspect
    motor is defective.
    Separate terminal plate & repeat measurements,
    if readings do not improve rewind is probably
    required.

  2. #15
    Join Date
    Jan 2008
    Location
    windy city
    Posts
    4,430
    great procedure thumper

  3. #16
    Join Date
    Nov 2003
    Location
    Montreal, Qc.
    Posts
    780
    Quote Originally Posted by heavymetaldad View Post
    great procedure thumper
    Thanks, and get well soon.

  4. #17
    Join Date
    Jul 2006
    Location
    Brooklyn , NY
    Posts
    24
    Application Engineering Bulletin
    AE-1294 August 1, 1992

    MEGOHM VALUES OF COPELAND COMPRESSORS

    ......There are many factors that affect megohm
    readings including contaminated refrigerant, oil
    level, refrigerant in oil and current leakage through
    electrical fusites or terminal plates.

    Any external electrical components connected to
    the compressor terminals also affect megohm readings.
    Wires, contactors and relays all leak current
    and will decrease compressor megohmeter readings
    if not disconnected.

    As mentioned earlier a single megohm reading
    cannot be used to condemn a compressor since
    many other factors are involved. However, limits can
    be placed on megohm values that dictate action be
    taken. Copeland has found that these limits are
    related to the rated voltage of the compressor. Megohm
    values equal to or greater than 1000 ohms per
    volt are probably acceptable. For example, a 460 volt
    compressor might show a megohm reading of 460,000
    ohms or 0.46 megohm. Compressors with rated
    voltages of 208 to 230 volts would then be operable
    at megohm values of 0.208 to 0.230 megohms; for
    simplicity, Copeland has set the limit at 0.5 megohms
    before a compressor is condemned.

  5. #18
    Join Date
    May 2004
    Location
    Sunny Mid South
    Posts
    508
    Quote Originally Posted by valentyn View Post
    Application Engineering Bulletin
    AE-1294 August 1, 1992

    MEGOHM VALUES OF COPELAND COMPRESSORS

    ......There are many factors that affect megohm
    readings including contaminated refrigerant, oil
    level, refrigerant in oil and current leakage through
    electrical fusites or terminal plates.

    Any external electrical components connected to
    the compressor terminals also affect megohm readings.
    Wires, contactors and relays all leak current
    and will decrease compressor megohmeter readings
    if not disconnected.

    As mentioned earlier a single megohm reading
    cannot be used to condemn a compressor since
    many other factors are involved. However, limits can
    be placed on megohm values that dictate action be
    taken. Copeland has found that these limits are
    related to the rated voltage of the compressor. Megohm
    values equal to or greater than 1000 ohms per
    volt are probably acceptable. For example, a 460 volt
    compressor might show a megohm reading of 460,000
    ohms or 0.46 megohm. Compressors with rated
    voltages of 208 to 230 volts would then be operable
    at megohm values of 0.208 to 0.230 megohms; for
    simplicity, Copeland has set the limit at 0.5 megohms
    before a compressor is condemned.
    Thanks! I bought a megger a few months ago. Hadn't had a chance to figure out how to use it. This helps me get a feel for it. This thread is long out of play, so don't know if it will be seen, but what Megger setting recommended?
    -Surf Life Hard!!!-

  6. #19
    Join Date
    Oct 2001
    Posts
    6,966
    smell the freon off the suction it went NUKE..your cooked
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  7. #20
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,659

  8. #21
    Join Date
    Mar 2001
    Location
    Seattle
    Posts
    384
    Quote Originally Posted by Sun Dog View Post
    Thanks! I bought a megger a few months ago. Hadn't had a chance to figure out how to use it. This helps me get a feel for it. This thread is long out of play, so don't know if it will be seen, but what Megger setting recommended?
    Download "a stich in time". Its a really long read and some of it is not related to what we do but it gives you more insight into megging.

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