Article 230.42(A) of the 2002 NEC covers sizing service entrance conductors:
Why does the continuous or non-continuous rating of the breaker affect the size of the conductors
Assume I forget to include 125% of the continuous loads in my calculations for the service conductors (I use 100% instead). The inspector comes out and tells me the service conductors are undersized. By replacing the breaker with one that has a 100% continuous rating, the conductors are now sized correctly. This makes no sense to me. Does anyone have a clue WHY?
Steve
Code:
230-42. Minimum Size and Rating
(a) General. The ampacity of the service-entrance conductors before the application
of any adjustment or correction factors shall not be less than either (1) or (2).
Loads shall be determined in accordance with Article 220. Ampacity shall be
determined from Section 310-15. The maximum allowable current of busways
shall be that value for which the busway has been listed or labeled.
1. The sum of the noncontinuous loads plus 125 percent of continuous loads
2. The sum of noncontinuous load plus the continuous load
if the service-entrance conductors terminate in an overcurrent device where both
the overcurrent device and its assembly are listed for operation
at 100 percent of their rating
Assume I forget to include 125% of the continuous loads in my calculations for the service conductors (I use 100% instead). The inspector comes out and tells me the service conductors are undersized. By replacing the breaker with one that has a 100% continuous rating, the conductors are now sized correctly. This makes no sense to me. Does anyone have a clue WHY?
Steve