• posted

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

1. various 120 V lighting loads ( track lighting, outside lighting, show window lighting, etc)
2. 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 calculations?

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 ).