article 517 ques.

[wireman1]

517 a & b if the main circuit breaker rated 1200 amps is gfp proteced at the service do you have use gfp protection for all the breakers will feed sub panels down stream? what if you feed off of one of the sub panels down stream to another sub panel such as from a 800 sub to a 400 sub must the 400 amp breaker be gfp proteced also ?does it just keep continuing like that

 

[charlie b]

You have to take it one level down, but no further than that. If for example the main is 1200 amps, and if it has GFP protection, and if the only breakers on the main are six 800 amp feeders, and if there are other subpanels (each 400 amps) further downstream from the 800 amp panels, then on the main board all six of the 800 amp breakers need GFP, and none of the subsequent 400 amp breakers need GFP.

 

[bphgravity]

And don't forget part C of the section. Selectivity of the ground-fault protection is as crucial as the ground-fault protection itself.