J
jh
- Jan 1, 1970
- 0
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
calculations?
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 ).
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
calculations?
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 ).
