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Thread: Allowable lighting on 15 amp circuit

  1. #1
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    Allowable lighting on 15 amp circuit

    I'm just finishing the wiring on my new basement shop and planned on having 18 - 4' 32 watt T8 fixtures. Based on my calculations this equates to approximately 10 amps.

    Does anyone see an issue with running this many lights on a 15 amp dedicated circuit?

    Thanks,
    Wes Billups

  2. #2
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    32 W X18= 576
    I=W/E
    576/110=5.24 Amps

    Looks good to me

    I would split it onto 2 circuits only to gove me the ability to deenergise one while working on the other but thats just me.
    "Thereís a lot of work being done today that doesnít have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesnít have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  3. #3
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    Don, thanks for the response. I should have mentioned each fixture contains 2 bulbs so my calculation was 18 fixtures x 2 bulbs/fixture x 32 watts/ bulb divided by 110 volts. That's how I came up with 10.5 amps.

    I'd like to keep it to one circuit as my house panel is already pretty full. The shop is fed from a sub panel and I didnít want to put the light circuit in this panel. My reasoning is that if something catastrophic happened I figure Iíd still have light in the shop if the sub panel blew.

    Iím planning on using two switches to each control half of the lighting. This way if I am just running in to do something quick or non-detailed work I can only kick on half the lights.

    Let me know if 10.5 amps of continuous load is too much for a 15 amp circuit? There should never be any more than this as there are no other loads on this circuit, all of the outlets are fed from my sub panel.

    Thanks again,
    Wes Billups

  4. #4
    Quote Originally Posted by Wes Billups View Post
    Don, thanks for the response. I should have mentioned each fixture contains 2 bulbs so my calculation was 18 fixtures x 2 bulbs/fixture x 32 watts/ bulb divided by 110 volts. That's how I came up with 10.5 amps.

    I am not totally sure but somehow It lingers in my mind that you are only allowed 12 fixtures on one circuit. I can check with my son (Master electrician) or if there are electricians in the loop, they might have the answer.

    As for number of circuits and a full panel, I added circuits to my panel using "piggyback breakers" they are two breakers on one unit allowing two wire runs, These are allowed as long as you don't exceed the main or the total capacity of the box.

    For reasons mentioned before, I think I would go with two wire runs so that you have the option of shutting down one side whilst you operate on the other. Or something like that. Also allows to lower the light needed and conserve power when Sun Light exposure is not needed.

  5. #5
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    10.5 amps is fine. Usual guideline is 75% of rated load, which would be 11.25 amps for a 15 amp circuit. You can always call your local building department and ask them.

    Just occurred to me, if you want them seperated, you could use two switches on the same circuit, such as if one of those dual half-size breakers were not available for you panel.
    Last edited by John Dow; 03-21-2007 at 12:48 AM.

  6. #6
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    I assume you mean 9 two-lamp fixtures, which will only draw about five amps at 120v~. So, you could put them all on one breaker.

    I'd be inclined to split them over two breakers, though, so that if - for some unforseen reason - one breaker blows, you won't be totally in the dark. Think about having your hands close to a tablesaw blade, jointer blade or router bit when the lights suddenly go out. Could be dangerous...
    Jim D.

  7. #7
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    You could always hook half of the lights to the existing "House" circuit, and hook the other half to a circuit from the sub panel, and this would give you a backup should ONE breaker fail.

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