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nec load analysis question

Discussion in 'Electrical Engineering' started by jh, Nov 16, 2006.

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  1. jh

    jh Guest

    I am currently studying for the journeyman exam using "Stallcup's Journeyman
    Electrician's study guide". I am currently in chapter 10: Commercial
    calculations. Whenever my answer differed from the books I re-read the nec
    and I would find my error. However now I can't see why my answers are wrong.
    I have two questions:

    1) in a commercial building ( say 120/240 V single phase three wire ) where
    the service load calculations for the neutral is greater that 200 A shouldn't
    article 220.61(B)(2) apply?

    2) in the book there are examples of the following:

    store building: 277/480 V 3 phase

    1. office area is 277 V lighting

    2. warehouse area is 277 V lighting

    various 480 V loads

    3. various 120 V lighting loads ( track lighting, outside lighting, show
    window lighting, etc)

    4. various 120 V receptacle loads ( multioutlet assemblies, continuous
    and non continuous receptacle loads, etc )

    For the neutral, the book adds the VA of 1,2, and 3. It then divides this by
    480*sqrt(3). Why didn't they add the load of 4 as well? The examples do not
    mention any type of transformer and I am at a loss as to why they would
    include the 120 V lighting but not the 120 V receptacle load in the neutral

    Thank you for your time.

    Note: If the book happens to be in error does anyone know where I can find
    the corrections posted? ( I have searched but found nothing ).
  2. jh

    jh Guest

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