NEC 250.34(B) allows omission of a grounding electrode connection for a vehicle-mounted generator when certain conditions are met; in short, when:
- The generator and vehicle frames are bonded together,
- Equipment powered by the generator is either mounted on the generator or supplied by receptacles mounted on the generator,
- Proper bonding is done throughout.
My concern is with the second part of #2, which implies that if a piece of equipment is hard-wired to the generator instead of cord-connected there is a deficiency and that connecting the vehicle frame to a grounding electrode somehow corrects the deficiency. I do not understand the reason for this; assuming all other code requirements are met, just what is it about hard-wiring vs. cord-connection that necessitates this restriction?