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Multi family main breaker size

Merry Christmas

Frank D

Member
Location
Los Angeles, CA
Occupation
Electrical project manager
In a multi-family building we are replacing the old gear, (existing gear has no mains on 12 meter set) with new meters and a main disconnec.
We have a calculated load current of 513 amps.
using 513 X 1.25 = 641 So 800 amp breaker?

600 amp breaker max load at 80% = 480 amps
800 amp breaker max At. 80% = 640 amps

so either way 800 amp main breaker?
 
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