I got in rather heated conversations with ambulance manufactures, one in Ark and one here in Houston. They would install a small panel in the unit served by a shore power cord. They would hook the neutrals and grounds on the same buss. The panel would serve several chargers and on later units, onboard AC unit. The first complaint I got was when the EMT (Firefighter) unplugged the cord he would get a shock. When the cord was pulled, the neutral would break first making the chassis hot for a second. I isolated the neutral and solved the problem. Told the manufactures and they both said the NEC does not apply to them and that the way they wired the panels was correct. I sent a certified letter to both, telling them they would be libel if someone got killed. Some smaller fire dept. have substandard wiring. If you were to plug the unit into a ungrounded ckt with reverse polarity, the whole chassis would be hot. Speaking of campers, lots of campers were wired like this with the neutrals and grounds bonded together. They trip a GFCI real quick. Most have a 30a cord that is connected to a non GFCI ckt at the camp site. Trouble comes when someone uses a 30a to 15a adapter in a GFCI outlet. I agree camper supply co have some not so great adapters, a cord to plug a 30a in a 50a plug and such. In your case, I have less of a problem plugging a 30a-50a plug in a 15,20,or 30 ckt even if the single ckt supplies both poles than a 40-50a ckt suppling a 30a or less load. As long as the wire size matches the source breaker size. Robert
