All equipment grounds in a box are to be bonded (spliced) togther, even if they are on different circuits. This is NOT to be mixed up with noodles, for they should remain independant from other circuits.
Even though it isn't widely enforced, the 6" free conductor length also applies to EGC's, so the shortest one has to be 6" (with 3" available outside the box).
Sorry, book's in the truck, I'm lazy this morning, so no code refs...
-Virgil Residential/Commercial Inspector 5 Star Inspections Member IAEI
As to the "why" for tying the egc of one circuit to another (or others). . .this creates multiple parallel return paths for fault current. The egcs form a net or web. The overall resistance of the egc is reduced by the parallel resistances.
I use Buchan spice caps for the EG. Slide the cap over long ground leads (after twisting them together). Leave one lead for each device and if it’s a metal box leave one for that also. Then cut off the remainder. Also on rough in, I like to group the leads for each device and do a “barber pole” wrap with the ground wire.
sorry, i must be the worst at over-using abbreviations here
some tie all egc's together, and some only tie the 12awg's together and put the 14awg's together in separate crimp sleeves, 250.148 seems to say all egc's are to be tied together, but it says "where circuit conductors are spliced" so i guess they could argue that it doesn't say "where DIFFERENT[12awg, 14awg] circuit conductors are spliced" they have to be spliced together. so if all ciruits with egc's in a plastic box are required to be spliced together, why doesn't it get turned down by inspectors? i just saw this today.
Al, thanks, that's a different way of looking at the parallel path idea for me. i always thought of parallel paths as bad things.
about the decoder ring thing. maybe over in the left margin with the advertisements we could have a quick easy reference decoder ring listing of abbreviations of the top ten or so, think of all the bytes we could save my votes are for these. GEC grounding electrode conductor GC grounded conductor UGC ungrounded conductor EGC equipment grounding conductor BC branch circuit OCPD overcurrent protection device