In Part 1, we clarified what the National Electrical Code (NEC) is talking about in regard to "grounding" equipment. The equipment grounding conductor (EGC) is really a bonding conductor at the equipment end. It is, however, ultimately connected to ground at the supply.
Article 250, Part VII begins by telling us where the requirements are for this purpose [250.130]:
- If at a separately derived source, that connection must follow the requirements of Sec. 250.30(A)(1).
- If at service equipment, that connection must follow the requirements of Sec. 250.130(A) or (B).
So for a separately derived source, the requirements are all the way back in Part II (250.30, not 250.130). In essence, you must install an unspliced system bonding jumper from a single point on the separately derived source from the source to the first disconnecting means (or overcurrent device). Some other particulars are in Sec. 250.30, and it’s followed by three exceptions.
For service equipment, the connection depends on whether the system is:
- Grounded. Bond the EGC to the grounded service conductor and the grounding electrode conductor.
- Ungrounded. Bond the EGC to the grounding electrode conductor.
