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Thread: Electrical load calculation

  1. #1
    Join Date
    Jan 2006
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    12

    Electrical load calculation

    Hello all... We have Sample dwelling unit load calculation like 3VA per sqft for lighting and small appliance load and other factors like demand factor to size the incomer feeder.This is mainly for residential load calculation as per NEC.Do we have a sample load calculation for commercial & industrial electrical load calculation for a big IT company wich has more number of Computers,data centers,chiller & pump loads,fire fighting & sanitation pumps loads etc. for commercial application and also for a processing plants like cement,sugar,oil & refiners for industrial projects as per NEC.If so plz help me out my giving the link or reference.

    Regards
    Karthik

  2. #2
    Join Date
    Jan 2006
    Posts
    5

    Re: Electrical load calculation

    The NEC load calculation requirements are outlined in Article 220. All continuous loads are to be taken at 125 % demand factor and all non-continuous loads at 100 %. The exceptions are as listed in the article. (ie the first 10 KW of receptacle load shall be taken at 100 % and the remainder at 50 %). Also additional load calculation references are indicated in 220.3 for specialty equipment such as fire pumps, elevator feeds etc. Per 220.50 motor loads must be calculated per 430.25, 26 and 440.6 as applicable. With larger projects the service and load calculations become more complex and must be analyzed based on each individual component

  3. #3
    Join Date
    Jan 2006
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    12

    Re: Electrical load calculation

    many thanx for the quick reply.Can i have a sample calculation sheet for both commercial and industrial projects.

  4. #4
    Join Date
    Jul 2005
    Posts
    319

    Re: Electrical load calculation

    Can i have a sample calculation sheet for both commercial and industrial projects.
    I will suggest you purchase a referance book that will give a more detailed outline on commercial calculations I myself will be purchasing Mike Holts Commercial Load Calculations book, well worth the money.
    Joe from TEXAS

  5. #5
    Join Date
    Feb 2003
    Location
    Florida
    Posts
    7,294

    Re: Electrical load calculation

    This is not an all-inclusive procedure for sizing a service to a non-dwelling occupancy. Please reference Article 220 for exact code specifications.

    STEP 1 Use Table 220.3(A) (2005-220.12) and multiply lighting load va to total square footage. Feeder conductor at 125% for continuous load.

    STEP 2 Demand load for motel, hospital, warehouse. (Table 220.11) (2005-220.42) All others at 100%.

    STEP 3 Compare heat with A/C. Omit smaller. (220.21) (2005-220.60)

    STEP 4 Heavy-duty lampholders at 600va each. (220.3(B)(5)) (2005-220.14(E))
    Other outlets at 180va each. (220.3(B)(11)) (2005-220.14(I))
    Multioutlet assemblies each 5-foot at 180va each. (220.3(B)(8)) (2005-220.14(H))
    Show window lighting each linear foot at 200va each. (220.3(B)(7) (2005-220.14(G))

    STEP 5 Demand for receptacle loads over 10kva. (220.13) (2005-220.44)

    STEP 6 Demand for kitchen equipment. (Table 220.20) (2005-220.56)

    STEP 7 Largest motor increased by 25%. (220.14) (2005-220.50)

    STEP 8 Size the service by dividing the total va by the applied voltage. Use Table 250.66 to size grounding conductor. (It cannot be smaller than the neutral)
    Bryan P. Holland, MCP

  6. #6
    Join Date
    Feb 2003
    Location
    Alabama
    Posts
    2,627

    Re: Electrical load calculation

    The NEC does not help much on commercial caculations. As for demand factors for the loads you listed, you have to figure that out for yourself.

    [ January 06, 2006, 02:23 PM: Message edited by: bob ]

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