Knowing how important NEC issues are to our readers, we're introducing a new online Code Q&A column. Updated weekly, visit this link for answers to your latest Code questions and concerns.
Q. Let’s say a 5kW generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both. Should the generator have a ground rod connection? A point on the frame of the generator marked "ground" makes me think so.
A. No, a ground rod is not needed, not required, and would serve no purpose [250.34(A)]. This manufacturer provided a ground lug on the generator because it doesn’t know any better.
CAUTION: Creating a bonding jumper connection at both the source and the first disconnecting means will create a parallel path, allowing dangerous neutral current to flow over the grounding conductors or grounding paths, which is a violation of 250.6.
Q. Some of the journeyman electricians on my latest project believe the neutral and grounds should be connected together in a panel fed by a 480V to 120/208V transformer. I’ve always made this neutral-to-ground connection at the transformer, and kept the grounds and neutrals separated. Which method is correct?
A. You must make a neutral-to-case connection on the secondary of the transformer at any point from the source to the first system disconnecting means or overcurrent device [250.30(A)(1)]. It’s important to point out that this connection must be made at the same location as the grounding electrode connection to the grounded (neutral) conductor [250.30(A)(2)].
