Grounded Chassis v Floating Chassis Ground
If you ground 120 volt sysrem to the chasis and wire shorts out, you have now energized the whole bus which is sitting on rubber wheels totally ungrounded. Over the years ive seen three times . One coach you grab door handle you would feel a tingle standing on grass. For saftey, which is what the ground system is should go off the bus back to feed. Get any code book in the country, it will tell you how to hook up a sub panel ,which a camp ground feed the bus becomes the sub panel.
Demac clears up one part to this discussion (thanks Demac!). I'll mention another. There's a lot of detail so brothers and sisters please check my work!
For the moment let's take the inverter/charger or any transfer switches from battery power out of the equation and focus just on grounding and shore power. Assume three wires are coming into the bus from shore power: black, or load (or hot); white, or neutral (or common); and green or ground.
Grounded Chassis:
If the bus 120VAC subpanel is grounded to the bus chassis via a conductor connecting the ground bus bar in the subpanel to the metal chassis, and if that ground bus bar is NOT bonded to the white, or neutral (or common) bus bar in accordance with electrical code, you should see the following:
1. A test tool like a plug-in receptacle tester on any properly wired branch circuit will show proper ground. In this case, the ground is somewhere back to the shore power or beyond, to the main panel.
2. Any dead short of that branch circuit to metal within the bus that is connected to the chassis will trip the branch circuit breaker at the bus subpanel, as you want it to.
3. Any voltage bleed-over due to a partial short
that is insufficient to trip the circuit breaker in the bus subpanel may give you a tingle to a shock if you touch it while in contact with the bus chassis when you are inside the bus.
4. Any hot wire that you come in contact with, either because it is just dangling there and you grab it, or because you come in contact with something conductive that it is touching (something not connected to the bus chassis so it hasn't already tripped a breaker) will give you a jolt, or kill you, if you are in contact with the bus chassis inside the bus.
In other words it is just as safe or unsafe as your residential wiring.
Similarly,
- If condition #3 exists and you are outside the bus, you may also get a tingle to a shock because your shore power is not just bonded between neutral and ground at your pedestal or shore power panel; it is also grounded to earth, literally, and your body completes the circuit. It is just less likely to come through the bus chassis.
- If condition #4 exists and you are outside the bus, you may also get a jolt or get killed for the same reason mentioned above.
Floating Chassis Ground
If you choose NOT to ground electrical devices and the ground bar of the subpanel in the bus to the bus chassis you will reduce the chances that standing on the ground and making contact with a conductive wire or surface ('hot skin') due to a short will give you a tingle, shock or get you killed. This is because there are fewer (or no) conductive paths to the chassis, so less chance you complete a circuit through your body.
As a side note you are also less exposed to bootleg ground reverse polarity shock, but this condition is wicked easy to check for before you plug in to that pedestal and it shouldn't factor in to this design discussion--you should
always test shore power before plugging in.
Counterpoint to Floating Chassis Ground:
Grounding everything to chassis
reduces the chances that condition #3
will occur in the first place because there are
more ground paths, increasing the likelihood the breaker will trip, reducing the risk of shock while in the bus.
Similarly, there are fewer ways condition #4 can exist. Think of a shorted motor, or a worn wire inside a light fixture: if those motors and light fixtures are grounded to chassis that breaker is more likely to pop.
My takeaway: Grounding everything to the chassis less risky than not.
Beeb2, still eager to hear the results of your ground test while that inverter/charger is on shore power.
Huh? 
.
information which YOU select as pertinent. Please, attach some photos of your panel and you grounding system so WE can suggest the corrections. It's quite possible that you have not identified the causes or specific information to relay to us and in turn omitted data valid to the solution.
Pictures man. Why make it difficult for the folks trying to help you?
but it's not
, so your eyes don't notice.
