Q. What are the rules in using the neutral conductor for bonding of metal parts?
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The neutral conductor can be used as the circuit equipment grounding conductor on the supply side or within the enclosure of the service disconnect in accordance with Sec. 250.24(B) [250.142(A)(1)].
The neutral conductor can be used as the circuit equipment grounding conductor at the source of a separately derived system or within the enclosure of the system disconnecting means in accordance with Sec. 250.30(A)(1) [250.142(A)(3)].
DANGER: Failure to install the system bonding jumper as required by Sec. 250.30(A)(1) creates a condition where dangerous touch voltage from a ground fault won’t be removed.
Except as permitted in Sec. 250.30(A)(1) for separately derived systems and Sec. 250.32(B) Exception for separate buildings/structures, the neutral conductor isn’t permitted to serve as an equipment grounding conductor on the load side of service equipment [250.142(B)].
Exception No. 1: In existing installations, the frames of ranges, wall-mounted ovens, counter-mounted cooking units, and clothes dryers can be connected to the neutral conductor in accordance with Sec. 250.140 Exception.
Exception No. 2: The neutral conductor can be connected to meter socket enclosures on the load side of the service disconnecting means if:
- Ground-fault protection isn’t provided on service equipment,
- Meter socket enclosures are immediately adjacent to the service disconnecting means, and
- The neutral conductor is sized in accordance with Sec. 250.122, based on the ampere rating of the occupancy’s feeder overcurrent device.