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  1. #1
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    Copeland compressor curve

    I need to check a compressor that is 208 volt. I believe the ratings on the curves are at 230 volt right? What is the formula to check amp draw at 208 volt? Can't remember. Thanks

    It's a three phase too.

  2. #2
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    Could you not derate it by the same percentage ?

  3. #3
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    The amp draw is inversely proportional to the supply voltage, so it's

    (Rated Volts) / (Actual Volts) x Rated Amps = Actual Amps

    For 208V, the proportion would be 230/208 or x 1.105 or about +10%

  4. #4
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    OK. AND BECAUSE THE PERFORMANCE CURVE DOSEN'T SAY do we assume all curves are published at 230 volts?

    This one is showing 10 amps at my evap/condensing temps. It's three phase. I should be able to clamp around either t1,t2, or t3 to measure that 10 amps correct? I have used this a fair amount, but all on single phase so far.
    And with the correction, expect to see 11.1 amps.

  5. #5
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    Quote Originally Posted by kklobas View Post
    OK. AND BECAUSE THE PERFORMANCE CURVE DOSEN'T SAY do we assume all curves are published at 230 volts?

    This one is showing 10 amps at my evap/condensing temps. It's three phase. I should be able to clamp around either t1,t2, or t3 to measure that 10 amps correct? I have used this a fair amount, but all on single phase so far.
    And with the correction, expect to see 11.1 amps.
    Copeland used to have the voltage correction noted on their printed performance curves...back in the day when they were real plotted curves. I recall seeing it more recently, but I forget where that was.

    Yes, you have the 3-phase correct. The curve assumes equal amps on each leg, but as we know, that isn't always the case. I usually take the average of the three amps measured and compare that to the expected amps.

  6. #6
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    Quote Originally Posted by icemeister View Post
    Copeland used to have the voltage correction noted on their printed performance curves...back in the day when they were real plotted curves. I recall seeing it more recently, but I forget where that was.

    Yes, you have the 3-phase correct. The curve assumes equal amps on each leg, but as we know, that isn't always the case. I usually take the average of the three amps measured and compare that to the expected amps.
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