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Service entrance conductor size

H

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
I have 1200A CT cabinet that feeds service trough. The trough feeds four separate main service disconnects fused at following: disconnect #1 fused at 400A, disconnect #2 is fused at 400A, disconnect #3 is fused at 400A, disconnect #4 is fused at 600A.

The service entrance conductors in trough is 3 sets of 4#600kcmil which is 1260A. The total overcurrent protection rating of all four service disconnects is 1800A.

The total demand load for the service calculated is 1,198A.

Since the total of all four service disconnects is 1800A and the service entrance conductors is 1260A, inspector flagged it saying total overcurrent protection size of the four service disconnects cannot exceed 1260A since service entrance conductors feeding it are 1260A.

The engineer stated you can and said according to NEC 2017 Article 230.90(A) exception no 3 you are allowed to have total of four service disconnect overcurrent rating exceeding the service entrance conductor amapcity since demand load (1198A) does not exceed service entrance conductor ampacity.

Is the engineer correct or the inspector? Which one?
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
hhsting said:
The service entrance conductors in trough is 3 sets of 4#600kcmil which is 1260A. The total overcurrent protection rating of all four service disconnects is 1800A.
Click to expand...
I agree the inspector is incorrect. The total ampacity of the four OCPD's is irrelevant.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
230.80 Combined Rating of Disconnects. Where the service
disconnecting means consists of more than one switch or
circuit breaker, as permitted by 230.71, the combined ratings of
all the switches or circuit breakers used shall not be less than
the rating required by 230.79.

Exception No. 3: Two to six circuit breakers or sets of fuses shall be
permitted as the overcurrent device to provide the overload protection.
The sum of the ratings of the circuit breakers or fuses shall be permitted
to exceed the ampacity of the service conductors, provided the calculated
load does not exceed the ampacity of the service conductors.
 
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