In regards to NEC 2014 250.122(B). Assume calculations show that a 370 wire sizing ampacity is required for a feeder, and #500 KCMI copper conductor is selected to feed this load from a 400 amp circuit breaker prior to upsizing for any reason with a #3 copper equipment grounding conductor (EGC). If, due to voltage drop, this feeder is changed to (2) parallel #250 KCMIL copper, to what size is the EGC to be increased to in this situation (as ratio of conductor sizes equals 1).
In parallel in (2) conduits. IE each parallel run in separate conduit.
Ok Doug, that makes it simple then.
250.122(B) would not apply here.
Since you are revising the installation with parallel conduit, you use 250.122(F). Install the EGCs full size, in compliance with 250.122 (last sentence). #3CU in EACH conduit. Simple. Don't "mush" the two codes together, they are separate requirements and you have to see them as such, and apply them accordingly. Yes, it stays the same size, in this particular case. Double-check with the registered design professional as they may want to go bigger anyway.
Thanks you. Just as I thought.
Douglas P. Matern, PE
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Anytime.
First we need to know if the revised installation is talking about conductors being installed in parallel, in multiple raceways.
"...this feeder is changed to (2) parallel #250 KCMIL copper"
How many raceways?