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Thread: Volt Amps

  1. #1
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    Volt Amps

    Have a site lighting drawing that say 20A circuits shall not exceed 1500VA and 15A circuits shall not exceed 1150VA. How do I make sure I don't put too many light poles on one circuit? Do I kneed to look at the fixture watts? Thanks.

  2. #2
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    Quote Originally Posted by mstrlucky74 View Post
    Have a site lighting drawing that say 20A circuits shall not exceed 1500VA and 15A circuits shall not exceed 1150VA. How do I make sure I don't put too many light poles on one circuit? Do I kneed to look at the fixture watts? Thanks.
    Yes, you need to start with the fixture watts, and know what bulb and driver will be fitted if there are options.
    Then you look at the power factor (PF) of the fixture and divide the watts by the power factor to get the VA.

  3. #3
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    Quote Originally Posted by GoldDigger View Post
    Yes, you need to start with the fixture watts, and know what bulb and driver will be fitted if there are options.
    Then you look at the power factor (PF) of the fixture and divide the watts by the power factor to get the VA.
    Thanks.

  4. #4
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    Quote Originally Posted by mstrlucky74 View Post
    Thanks.
    many times the fixture data sheet will list the amps
    if it does va/fixt = voltage x amps
    divide that into total va to get number of fixtures



  5. #5
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    Must be 120 volt circuits in your application, 1500 VA on a 277 volt circuit is only about 5.4 amps, advantages of using 277 over 120 kind of go away if you are still limited to 1500 VA.

  6. #6
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    Quote Originally Posted by GoldDigger View Post
    Yes, you need to start with the fixture watts, and know what bulb and driver will be fitted if there are options.
    Then you look at the power factor (PF) of the fixture and divide the watts by the power factor to get the VA.
    Wouldn't the ballast or driver have all of that figured out and just give you the amount of current it draws?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  7. #7
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    Quote Originally Posted by infinity View Post
    Wouldn't the ballast or driver have all of that figured out and just give you the amount of current it draws?
    It should. That would be the easiest path.
    In some cases the driver may not give the current for each possible voltage or voltage range.

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