Sizing subpanel feeders

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JES2727

Senior Member
Location
NJ
When sizing feeders for a subpanel are they sized according to the main breaker or the connected loads? Is it permissible to feed a 200A 120/208V 3-phase subpanel with 4/0 aluminum if the connected load is less than 180A? 4/0 AL is rated for 180 amps, 240.4(B) allows us to protect it at 200A...
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Yes. You size the feeder for the load, and then protect the feeder according to 240.

The code does not prohibit spending more money than you need to meet the minimum ampacity requirements, as long as the breaker protects the conductors.
 
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