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    Lighting Demand Factor

    Regarding commercial buildings, lighting branch circuits: we add up the lighting fixture wattages and always use 125% for demand factor for the load because lighting is continuous load. Is this wrong? I'm trying to have it proved that it's right by NEC, but....Looking into NEC 2014 210.20(A), 125 percent is required for the overcurrent protection and not for load. NEC 2014 table 220.42 shows the lighting load demand factors, where for a commercial office building the demand factor would be 100%. Is there any other section of the NEC which tells us that commercial office building lighting load demand should be at 125%? Thank you!

    #2
    The lighting demand factor for an office is 100%. The 125% for continuous load is not a demand factor.

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      #3
      Originally posted by david luchini View Post
      The lighting demand factor for an office is 100%. The 125% for continuous load is not a demand factor.
      Thank you!

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        #4
        Originally posted by curious101 View Post
        Regarding commercial buildings, lighting branch circuits: we add up the lighting fixture wattages and always use 125% for demand factor for the load because lighting is continuous load. Is this wrong? I'm trying to have it proved that it's right by NEC, but....Looking into NEC 2014 210.20(A), 125 percent is required for the overcurrent protection and not for load. NEC 2014 table 220.42 shows the lighting load demand factors, where for a commercial office building the demand factor would be 100%. Is there any other section of the NEC which tells us that commercial office building lighting load demand should be at 125%? Thank you!
        I think you have to use the VA per square foot values in the table, unless your actual fixtures draw more than that value.
        Ethan Brush - East West Electric. NY, WA. MA

        "You can't generalize"

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          #5
          Looking for some clarification... So lighting demand factor is 100%. Continuous loads are 125%. Lighting fixtures that are used in everyday operation are considered continuous loads so essentially get a 125% demand factor applied right? So the only 100% demand factor for lighting would be like lamps or plug in fixtures?

          I'm trying to piece these two threads together. https://forums.mikeholt.com/forum/ac...in-nec?t=52496

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            #6
            Originally posted by WA_Sparky View Post
            Looking for some clarification... So lighting demand factor is 100%. Continuous loads are 125%. Lighting fixtures that are used in everyday operation are considered continuous loads so essentially get a 125% demand factor applied right? So the only 100% demand factor for lighting would be like lamps or plug in fixtures?

            I'm trying to piece these two threads together. https://forums.mikeholt.com/forum/ac...in-nec?t=52496
            The 125% is not a "demand factor." See 220.40 - The calculated load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied...after any applicable demand factors permitted by Part III or IV or required by Part V have been applied. There is nothing in Part III, IV or V regarding 125%

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