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Thread: How many lights on a 15 amp breaker

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  1. #1
    DIY Member Zenman's Avatar
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    Default How many lights on a 15 amp breaker

    Redoing the basement lighting circuit. Is there a code or general rule of thumb when it comes to how many lights can be put on a 15 amp circuit?

    I am familiar with how to convert between watts and amps. And I know how to figure out how many 100 watt bulbs can be on simultaneously before blowing the breaker, but was curious what the pros do. Do I max it out since it is unlikely that all the lights will be on at the same time OR leave 20% of the available 15 amps unused???

    Thanks!

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    DIY Member Lightwave's Avatar
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    Full load draw on a lighting circuit should not exceed 80% of the breaker rating. For example, no more than 14 100w fixtures on one 15a circuit.

    You have to take ballast inefficiency into account if you're using fluorescent lights.

  3. #3
    DIY Member Zenman's Avatar
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    Ok... I thought I remembered hearing an 80\20 rule on this but wasn't sure... I do have some florescent fixtures, so I'll look into that as well. Thanks!

  4. #4
    Licensed Electrical Contractor Speedy Petey's Avatar
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    There is no 80% rule with regard to residential lighting, unless the circuit is heavy and us expected to be on for 3 hours or more. ALL lighting general use receptacles are taken into account in the load calculation
    Common sense just prevails here.

    I know Canada has different rules on this than the US. So to the OP keep this in mind.
    Answers based on the 2008 & 2011 NEC. If you're on the '14 already I feel sorry for you.

  5. #5
    DIY Member Zenman's Avatar
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    Thanks for the reply. And yes I'm in the US.

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    Licensed Electrician andrew79's Avatar
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    i'm pretty sure i recall somewhere that a pure lighting load can be loaded to 100%.....having said that i'm not positive and the general rule of thumb is always 80%....which is 12A not 14A as mentioned above. We normally run a max of 11 lights on a circuit.

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