Originally Posted by wmtire
I would suggest sending Mike Sokol (jmsokol) a PM. He is extremely knowledgeable in this subject and always is trying to help out. He's a real good guy.
This is Mike Sokol from the No~Shock~Zone. Golly, I'm blushing...
The general idea of AC grounding is that you need a solid connection from the incoming shore power line ground wire (called the EGC - Equipment Grounding Conductor) to the chassis of the RV. The reason for this is indeed to provide a fault current path for any sort of shorted wire or electrically leaky appliance. Note that the green EGC (ground) wires must maintain isolation from the white Neutral wiring inside your RV. There's lots of reasons for this in both the NFPA-70E National Electrical Code and the RVIA build code, but from a practical standpoint an internally bonded Ground-Neutral connection will make your GFCI's trip under ANY load.
Note that without the EGC connection to the RV frame it's possible for the chassis/skin of your RV to be energized at 120-volts with anywhere from a few mA (milliamps) to 20 or more amperes of available current. That's dangerous because standing on the damp ground and touching the skin or door handle of your RV can kill you. I think there was another thread here the other day where some RV technician was testing the RV with an ungrounded shore power connection and stated that the grounding was causing the circuit breakers to trip. That could only occur if the Neutral and Ground were bonded inside the RV itself. As others here have noted, your RV will probably require a Ground-Neutral bond externally when running from a floating neutral generator. And just about all Honda and Yamaha inverter generators are indeed neutral floated. But try as I may, I can't get Honda to even send me a demo EU2000i to video and write about this.
The confusing part of this grounding/bonding stuff is that for the 12-volt DC system the frame/chassis indeed does carry the return current for the DC appliances, and there's no separate EGC ground wire. And to make it even more crazy, in 12-volt DC systems the black wire is chassis/ground, with a red positive wire. While in 120-volt AC systems, the black wire is "hot" while the white wire is the return current, and the green ground wire is the fault current EGC (Equipment Grounding Conductor).
And no, there's no confusion between the 120-volt AC and 12-volt DC electrons. They indeed know where to go in various loops and paths.
In short, the chassis of your RV needs to be "bonded" to the incoming EGC "ground" wire from your shore power line. The Neutral and Ground wires inside of your RV must maintain electrical separation. Those same Neutral and Ground wires will be bonded externally when plugged into pedestal or home power. When running form a generator, you may need to "bond" the Neutral and Ground wires together at the generator itself, which can be my simple G-N bonding plug. You'll be forced to create a generator G-N bond if you're using a Progressive Industries EMS surge protector since if it detects an open "ground" it will shut down the power. Progressive Industries is aware of this and will be offering a pre-wired G-N bonding plug on their website soon, along with selling my No~Shock~Zone book there. There's really no need to earth-ground a portable or built-in generator for an RV unless you're distributing AC power to multiple receptacle drops.
Let me know if this makes sense to you.
BTW: I've been pitching the idea of teaching some on-site seminars about RV wiring and safety at FROG conventions this summer, but I'm not getting any traction with the idea. However, I'm a firm believer that education makes RV owners safer, so I'm doing my best to teach consumers and technicians about RV wiring and electrical safety even though I have zero budget for this. It's just a shame that the RV industry won't support electrical safety education.