yo jimmy,
be sure that your neutral bus is not "bonded" (electically continuous) to the chassis of your breaker box. only the grounds should be bonded to the box. also, Code requires that you physically bond your trailer and all electrically conductive parts inside to the ground.
these three pictures show a good example:
notice that the neutral bus is insulated from the chassis by being mounted on a piece of plastic.
i know i've posted this before but sometimes its hard to follow a 5 page thread with lots of bs in between.l
(EDIT: oops, that was the other grounding thread)
