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Thread: load calculation for a store

  1. #11
    Join Date
    Oct 2014
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    United States, Indiana
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    Quote Originally Posted by jeremy.zinkofsky View Post
    Sounds like you've already done most of the legwork by getting nameplate data of the large equipment.

    You can simply add up the VA of each piece of equipment to determine your load there. The NEC does not dictate the application of demand factors, you need to use best judgement there depending on its use. However, an appliance is generally considered to be a continuous load where a motor can be classified as intermittent or continuous.

    Receptacle count is straight forward per NEC. 100% for the first 10KVA, 50% of the rest with each receptacle rated for 180VA.

    Lighting you can get from square footage using 1-3VA per sq. ft. I would take a look at your local energy conservation code which will tell you the maximum lighting power densities allowed per type of space. You can get a better idea of what Watt per sq. ft you would need that way.

    If reasonable, you can get historical demand data from the utility which will tell you exactly what you are looking for.
    I called the utility, they said they can not give me KW hrs only $. $1200 per month on a 12 month average. They said I would need to contact the owner for KW r usage. I hate to bother the workers, manager, son of the owner, etc.,they are always so busy with customers

  2. #12
    Join Date
    Dec 2006
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    Eastern Oregon
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    Are you just trying to do a quick and dirty load calc or something you need to present to an inspector?

    We have a Fluke logger we install on services, etc for 30 days for things like this. If you have time to wait, this is the option I like best, assuming I can't get the info I need from the utility company.

  3. #13
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    Feb 2003
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    New York, 40.7514,-73.9925
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    220 for commercial is very conservative because it doesn't offer any significant demand factors like there is for residential. You can't arbitrarily say that you think only one lift runs at any given time on average.

    Your best bet to get any real sense of the load is per NEC 220.87 get it from their bills or put a meter on it for 30 days as mentioned in the previous posts.
    Ron

  4. #14
    Join Date
    Dec 2007
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    NE Nebraska
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    Quote Originally Posted by ron View Post
    You can't arbitrarily say that you think only one lift runs at any given time on average.
    No but reality and duty cycle of those is in a place you can still sort of forget they even exist to some extent. OP could probably have 5 run at same time and still never have a problem overloading anything, they just don't run long enough to be a problem. I haven't seen one that doesn't require operator to be standing there holding switch to raise it. That also means that is one less person available at that time to operate some other machine.

    I bet if you put all nine that OP has on a 60 amp feeder you never trip the feeder, maybe even if you intentionally ran all 9 at once. It might draw more then 60 amps, but they can't run more then maybe 20-30 seconds max - they have reached their travel limit by then.

  5. #15
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    Feb 2003
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    Quote Originally Posted by kwired View Post
    No but reality and duty cycle of those is in a place you can still sort of forget they even exist to some extent.
    Agreed, but nowhere in 220 does it let you forgive any of those loads in a calculation.

    That's why he is better off using the bill or meter method
    Ron

  6. #16
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    Dec 2007
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    NE Nebraska
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    Quote Originally Posted by ron View Post
    Agreed, but nowhere in 220 does it let you forgive any of those loads in a calculation.

    That's why he is better off using the bill or meter method
    I know. If you are in a place that wants plans review then you have more of a problem. If no plans review - a typical EI will seldom question load calculations on service or most feeders unless something seems pretty obviously wrong.

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