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  1. #1
    Join Date
    Mar 2011
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    HVAC Compressor overload question

    I have a compressor with 52A RLA, 72A max amps and a 90A (1.75 x RLA) thermal mag circuit breaker protecting it. If the compressor draws 80A of current, will the compressor be damaged by being overloaded (since it is under 90A) or will it trip out on overload after a while?


  2. #2
    Join Date
    Mar 2012
    West Chester, PA
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    52 RLA = rated or run load amp - what the motor should draw while turning it's design load
    72 FLA = you are calling MAX amp is the full load amperage - maximum amperage that the motor can draw before over heating

    if your compressor is pulling 80 amps then it is either overloaded or has a bad bearing or lack of lubrication of a failed capacitor (if single phase) the motor will open on thermal overload if it pulls this amperage for any period of time. While the thermal overload will proctect the motor to a certain extent, if the motor is left to cycle on and off, eventually either the thermal overload or the windings will fail.

  3. #3
    Join Date
    Jul 2000
    Northern Wisconsin
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    If the excessive amperage is being consumed at the compressor itself there's mainly one thing it's being "used" for........ generating heat in the motor winding.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  4. #4
    Join Date
    Jan 2005
    Houston TX
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    Your overload is a time / current overload, at 100% RLA no trip. Any thing over that is based on the class of the overload, be it 10, 20 or 30. That's the number of seconds it will hold with out tripping at 600% load. Anything between 599% and 101% of RLA is time weighted. The higher the current draw over RLA the faster the trip time. GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

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