3 vs 4 wire feed to garage

[rmeier2 (Robert Meier)]

@dkostenbader

I was wondering if anyone could explain the need for a four wire feed to a separate building apart from the house. In the case of the house I looked at today there was a separate garage with a subpanel fed by a three wire overhead feed. The grounds and neutrals were separate. To my knowledge there wasn’t any water or gas line going out to the garage. This should be a four wire feed, correct? And wasn’t this a relatively recent change to the code?

Thank you as always.

Up until the 2008 NEC code cycle 3 wire feeders were permitted if there were no metallic paths between the two structures. From 2008 and beyond a 4-wire feeder is required. If there is an old 3-wire feeder you must bond the neutral just like in a service and connect the GEC from your grounding electrodes to the neutral.

With a 4-wire feeder the EGC’s and neutrals are separate and the GEC goes to the EGC bus which is bonded to the enclosure, the neutral is left floating.