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electrical load question

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  • electrical load question

    I have a job coming up where the clients
    want to add 9 halogen light fixtures in the ceiling.
    The ceiling has no crawl space and currently there are
    no wires at all in the ceiling to start out with.

    of course there are electrical outlets on the wall and my idea
    would be to cut into the drywall and tap into the wall electrical outlets to bring power up to the ceiling but I don't want to
    overload the breakers, is there a electrical readout device
    that I could plug into the outlet and find out how much
    electrical load that particular breaker is currently serving?
    Your advice is appreciated


  • #2

    I'm a bit confused. You mention 'job' and 'client,' so I assume you're a professional, but your question indicates that you aren't a licensed electrician. Doesn't that kind of work need to be done by a licensed electrian, to pass inspection? And what do the codes in your area say about the number of fixtures/plugs that can be on a single circuit—wouldn't nine more be too many, and require a separate circuit?

    As far as determining the current load goes, you would have to know where every plug and fixture is located on that particular circuit, and what the uses are. With that, you can find out without a tool just how much draw there could be. For example, if a refrigerator is on the circuit, you would have to 'test' it while the motor was running, not idle, anyway, so you might as well pull the fridge out and check the amperage/watts/hp on the motor. Same with t.v.s, radios, and even light fixtures. Also, you need to figure in things like a vacuum cleaner being plugged in and used, or a hair dryer—both of which draw a lot of amperage. And what wire is available in the circuits that now exist—12/2 or 14/2? Wouldn't you be better off just running a new circuit? If the circuit breaker box doesn't have any room, you might be able to replace single breakers with those spiffy double mini-units.

    But, again, I would hesitate to do the wiring myself, in your current (forgive the pun) situation.

    Best of luck.

    Nolo illigitamati carborundum


    • #3
      I'm not an electrician, but I've done a fair amount of electrical work. You should realize from the beginning that most, if not all, local governments will require that you be a certified electrician or that a certified "master electrician" needs to nspect and certify your work.

      One of the basics of doing any kind of electrical work is the understanding that before you start doing anything, you need to know load/amperage that will be required by the devices you plan on installing. In the case of most Halogen lighting, they demand some significant amperage. Typically, Halogens run 300 to 1500 watts (depending on size of course). A 500 watt bulb presents a 4 amp load. Run four of those on a circuit and you easily exceed a typical 15 amp breaker and 14 gauge wiring. A 1000 watt bulb is 8 amps, and a 1500 watt buld is 12 amps. As you can see, you're going to need a sizeable circuit (wiring, breaker, etc.) to handle "several" halogens on one circuit. I don't think I would attempt to tap into an existing circuit for this kind of lighting. In addition, I surely wouldn't want to pay their electric bill. But maybe you are talking about those miniature halogen fixtures; either way, check the wattage and do the math to figure the amps. (Watts divided by 120 [volts] equals the amperage)

      But, to answer your question, as far as I know the only way to check the total load of the circuit would be to have every device that uses the circuit, fully operating and then check the amperage at the panel; OR, you could just check the amperage or wattage of each device (should be labeled on the appliance in some way) and simply do the math. However, the best and easiest way is to simply check the breaker for that circuit and see what it is rated for.

      Forgive me if I'm wrong, but it sounds like your experience is limited here; and if so, the wise thing would be to contact a local electrician.

      No disrespect intended, but I'd hate to see you get in a hassle with the local inspector or your insurance company,


      [ 05-19-2005, 01:39 AM: Message edited by: CWSmith ]


      • #4
        Max and CWS

        Thank you for the fast replies, both of you are 100% correct
        in picking up on the fact of my inexperience in this case.
        I agree with the suggestion in hiring an electrician do this
        type of work. I was hesitant to begin with on this situation.
        And now, after short consideration I am convinced that this should be done by an electrician.

        Again thanks for the insight and information.