subfeed protection

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320A service feeding an adjacent outdoor 3R fused disconnect/EPO.
It in turn shall feed two PB's within the building, in different locations.

If each PB has a main breaker of ~100A, does the cable from the disconnect to each PB need to be sized for 320A or ~100A?
I'd think 320 but something is tickling my memory about this.

The EC wants to instead install 2 disconnects/EPO at the meter, each fused at 100A. If so, do the PB's still need their own main breakers?

(My alternative is one disconnect followed by a 3R PB with 100A breakers feeding each PB, again [not] needing 100 PB mains.)
 
Your limited by either the 10 foot or 25 foot tap rule on the feeders if you don't want to run larger wire. If the panels in the building are farther than that you need two disconnects with 100 amp over current protection or a single panel with 100a breakers for each feeder. Panels inside could then be MLO.
 
Thanks. I assume there must be higher current/fewer slots panels for multiple 100A breakers but I've yet to find one.

(And SquareD just confirmed my fears...)
 
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Why not just install a 200a rated meter base with (2) 3r 100a Fused Disconnects or Enclosed Circuit Breakers to (2) 100a MLO Panels inside, or, if wanting to utilize the full 400a Service,
(1) 400a 3r Fused Disconnect outside to (1) 400a MLO indoor panel inside then to (2) 100a Subpanels from there?

Oh well....


JAP>
 
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