Here;s a situation I came across.
I know any time a metal mounting box is used for a duplex outlet the box
should be tied to the ground wire coming in.
What if the metal box/outlet is on the load side of an upstream GFCI?
Maybe codes say it still has to be grounded (?) but from a safety
standpoint is it pointless to ground the metal box?
As others mentioned, the NEC requires it to be bonded (connected to an
EGC). And there is an advantage to this even when the conductors are
Suppose the hot conductor faults to the box. If the box is bonded,
this will immediately create a short circuit and trip the circuit
breaker or GFCI. If the box is not bonded, nothing will happen until
you come along and complete a circuit with your body. If your body
connects the box to ground, this will trip the GFCI; but if your body
connects the box to neutral, it won't trip. Moreover, the hot
conductor to box fault could persist for a long time, long enough for
a second failure to occur, such as the GFCI going bad. Then there
would be nothing to protect you.
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