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Thread: I need help with this HVAC label.......

  1. #1
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    I need help with this HVAC label.......

    I can clearly see MOPD is 40A for this 460V 3 phase compressor.

    Next I see Minimum Circuit Ampacity is 31.9A

    Two or more people told me that this is the load. I disagree.

    The load is Fan Motor FLA(1.0*2) + Compressor Motor RLA (7.3+10.3) =19.6A

    Who is correct????Name:  HVAC Compressor Label.jpg
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  2. #2
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    I would use MCA divided by 1.25 for load.

    https://www.titus-hvac.com/softwares...ecalculate.pdf

  3. #3
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    The math is already factored in there use a 40a breaker or fuse with conductors suitable for 31.9 amps

    Sent from my SM-G950U using Tapatalk

  4. #4
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    The MCA is the largest component (usually the compressor) *125% + the other loads. Curious as to why do you need to know the actual load?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  5. #5
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    Quote Originally Posted by infinity View Post
    The MCA is the largest component (usually the compressor) *125% + the other loads. Curious as to why do you need to know the actual load?
    How about for feeder and service calculations?
    I live for today, I'm just a day behind.

  6. #6
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    Quote Originally Posted by kwired View Post
    How about for feeder and service calculations?
    Could be that's why I asked.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  7. #7
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    Quote Originally Posted by dionysius View Post
    I can clearly see MOPD is 40A for this 460V 3 phase compressor.

    Next I see Minimum Circuit Ampacity is 31.9A

    Two or more people told me that this is the load. I disagree.

    The load is Fan Motor FLA(1.0*2) + Compressor Motor RLA (7.3+10.3) =19.6A

    Who is correct????Name:  HVAC Compressor Label.jpg
Views: 869
Size:  134.0 KB
    19.6 is the maximum load it is rated for. Conditions of operation will determine actual load, but should not exceed that. Not sure just how they came up with MCA of 31.9, unless there is other load not on the nameplate for some reason. It is usually 125% of largest load plus all other loads. Even taking both compressor figures x 1.25 still doesn't get us all that close to 31.9.
    I live for today, I'm just a day behind.

  8. #8
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    West Chester, PA
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    kwired, I agree, that MCA is a puzzlement.
    Alternate current
    Line to ground and ground to line
    Current alternates

  9. #9
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    Quote Originally Posted by nickelec View Post
    The math is already factored in there use a 40a breaker or fuse with conductors suitable for 31.9 amps

    Sent from my SM-G950U using Tapatalk
    Elaborate on why you believe 31.9A is the running load. It cannot be that since it would heat up the wire.

  10. #10
    Join Date
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    Hawthorne, New York NEC: 2014
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    Running load is 19.6, the nameplate says wire it with conductors suitable for 31.9, not that the running load is 31.9, and use a maximum of a 40A breaker. So if you could find a 35A three pole you could use it.

    Apparently they are designing for the max starting draw and voltage drop.

    -Hal

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