Originally Posted by nat_ster
Yes DC grounds only to chassis and negative battery post. AC out from inverter only to isolated ground in AC panel. Keep AC and DC grounds apart. If anything ever malfunctions, you will be happy you did. Finding the problem will be much simpler.
Also no steel plug or light boxes attached directly to the bus steel. Make it imposable for your bus chassis and skin to become a live circuit.
I'll respectfully disagree on the ground advice based on personal experience. I have an older Xantrex modified sine inverter which specifically indicates in its instructions that its chassis is to be well-connected to the vehicle (and, thus, the dc negative/ground). One day while testing that thing on the shop floor I learned the "why" behind that instruction. At some point I found myself squatting beside the equipment with one hand resting on the shell of the inverter for balance while reaching to feel the temperature of an alligator clip on one of the battery terminals, and on touching that was much surprised to feel the familiar zing of 60 Hz ac biting back. It turns out that this inverter has its chassis internally connected to its ac ground and neutral terminals. This is a reasonable thing to do when fault currents and operation of GFCI protection are considered. Anyway, it turns out that if this inverter's chassis isn't connected to battery negative, then ~50V ac develops between those two and there's enough leakage current available to give a person a good zap when he unwittingly touches the wrong places at the same time. Think of a metal-bodied luminaire, a metal-chassis appliance which is either grounded or is double-insulated but has a fault, the grounded shell on the connector of the VGA/DVI/HDMI/USB/audio cable on that ac powered TV, and touching something on the bus body like a window or door or bench etc. Plenty of opportunity for surprises.
Consult the manual of your inverter to be sure. If the manufacturer doesn't specifically caution against it, I would definitely connect the inverter's ac ground to the bus chassis/body.
I can appreciate the idea behind avoiding metal junction boxes etc. It makes some sense in a shore-power-only scenario. But if there's an on-board inverter in the picture that's another story. Also I have some concern about whether such an approach defeats (ie prevents operation of) GFCI given that there's no ground to fault to.
One caution for any who might be thinking of both an inverter and
shore power (I am): beware the inverter's internal ground-neutral bond. You want that bond when the inverter is sourcing the power, but when things are switched over to shore power, it should be done in such a way that the inverter's internal ground-neutral bond is disconnected. If your transfer switch arrangement switches only the hot leg between inverter and shore, then when the shore power cord is plugged in it'll be connecting shore ground and neutral improperly. You'd need a multi-pole transfer, a plug-and-socket transfer, or some similar thing to keep the bonding appropriate.