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Thread: Tons to amps

  1. #1

    Tons to amps

    Is there a way to calculate an air conditioning load if all you have is the size of the unit in tons? Applied voltage is also known. 208v 1 phase - 4 ton unit. This is a hermetically sealed compressor.
    Gary FitzGerald

  2. #2
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    Re: Tons to amps

    I usually use 1.5 KVA per ton, for AC units in the 2-5 ton range, but it can vary a lot.

    Steve

  3. #3
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    Re: Tons to amps

    1 Ton of refrigerant =3.5 KVA. So if you 4 tons, you're looking @ 14 KVA or 14,000 watts. I=P/E. 14,000/208=67.3 amps
    5000 Ways, Chuze 1

  4. #4
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    Re: Tons to amps

    I usually use 1.5 KVA per ton, for AC units in the 2-5 ton range, but it can vary a lot.
    1 Ton of refrigerant =3.5 KVA
    How about a source??

  5. #5
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    Re: Tons to amps

    I have measured my own, very old, 3-ton unit at 19A @ 240V. That works out to 1.5KVA/ton. The breakers are 30A. 3.5KVA/ton sounds much too high for a modern AC unit.
    Don't mess with B+!
    (Signal Corps. Motto)

  6. #6
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    Re: Tons to amps

    "How about a source??"

    I used OC Conversion Pro: where 1 ton of refrigeration = 3,516.85284 volt ampere or 3.5 KVA.

    "I have measured my own, very old, 3-ton unit at 19A @ 240V. That works out to 1.5KVA/ton. The breakers are 30A. 3.5KVA/ton sounds much too high for a modern AC unit."

    Now that I think about it, That does sound kind of high, I may have done something wrong in my calculation. :confused:
    5000 Ways, Chuze 1

  7. #7
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    Re: Tons to amps

    So what do you do when you have to design for an essentially unknown load? Go huge?

    Do you try to go as small as you can to get the bid and hope you don't shoot yourself in the foot?

    The whole idea of doing this backwards seems unprofessional to me. (No offence intended towards you garyfitzgerald). I see this sort of dilema a lot.
    Sam, San Francisco Bay Area

  8. #8
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    Re: Tons to amps

    I've never done a lot of research on it. I do not deal much with compressor/condenser units of this size.

    But a general rule-of-thumb that I've used for 1-phase, 240V. units in the appx. 2 - 5 ton range is 1440VA per ton.
    This is close to steve66 1.5KVA.

    [ February 25, 2005, 08:32 PM: Message edited by: kiloamp7 ]

  9. #9
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    Re: Tons to amps

    A little background is in order here. About 1 KW is needed to drive a 1 hp motor,and about 1 hp is needed to drive a 1 ton AC compressor. Throw in some PF, and you have 1.5KVA/ton. This number may be a bit high for modern AC units though.
    Don't mess with B+!
    (Signal Corps. Motto)

  10. #10
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    Re: Tons to amps

    Another way

    One ton of frig.=12000 BTU
    1 watt=3.412 BTU

    4 tons x 12,000=48,000 BTU

    48,000/3.412=14,068 watts

    14,068/208 volts=67.63 amps.

    Ronald

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