Contractor Exam Prep - Unit 9 Challange question 34

[S-117]

This problem mentions that the load demand is 30,000 VA on an 120/240 V service

I have two questions.

1) why is the large voltage used to obtain a smaller amperage? This would be less conservative, no?

2) why is 75degree assumed in most problems when using table 310.15(B)(16) ?

 

[david luchini]

1) why is the large voltage used to obtain a smaller amperage? This would be less conservative, no?

No.

2) why is 75degree assumed in most problems when using table 310.15(B)(16) ?

See 110.14(C)

 

[S-117]

No.



See 110.14(C)

using smaller wire size is not less conservative?

please explain

 

[david luchini]

using smaller wire size is not less conservative?

please explain

The load will be connected to both legs of the 120/240V service. There is 240V between those two legs. The 30,000VA load will be 125Amps.

Using 250A of wire would be more conservative, it would be more wasteful.