120V Converter Grounding Question ??????

"Earth" is different from "ground" for RVs. So with the plastic frame, the house battery can't be "negative grounded" to the frame but the neg goes to the battery lug on the DC fuse panel which is grounded to the power centre metal case. All 12v circuits use wire for both neg and pos since the plastic "frame" cannot act as part of the neg path for any of the circuits.

If you had a metal frame, the 120v supply cord bare neg wire would go to the metal power centre case and then to the frame. The battery neg to frame connects via the frame to the metal power centre case.

So with no frame, the 120v ground stops at the metal power centre case and the battery neg gets to that power centre case via the battery lugs on the DC fuse panel. The 12v and 120v grounds are still in common. It just means there is no frame connecting them but so what?

The reason I asked this question is the Chassis of the unit I have is plastic. There is zero connection to the ground bar within the chassis and any ground other than the supply power cord wire. The instructions do not talk about grounding the ground bar. ( BTW...the "instructions" are horrible!)

It just seemed to me that the ground bar should be attached to the camper somewhere even though the truck camper is never actually grounded due to rubber tires?

westend wrote:
The converter 120 AC should be grounded through the ground wire in the supply wiring. If you wish to ground the chassis separately there is nothing bad about that but the chassis of the converter and the circuits are all connected inside the converter to supply ground.
I also commented in your other thread about using copper pipes as a ground plane, not best practices.
You should establish a new ground point for your electrical service.

The problem with using the converter's AC supply cord as the ground is wire size. The supply ground is connected to the case of the converter. Code requires a minimum of a #6 wire between the case of the converter & chassis or frame of the RV. Not sure on a truck camper, but if there is a fault on the 12V side of the converter to the case, enough current could flow to melt the supply cord ground (which, of course, is unfused). This is the reason for the #6 wire to the frame/chassis.

The shore power cord's bare copper ground wire should go to the power centre's metal case and then to the rig's frame. Its neutral goes to the neutral bus and the hot goes to the main breaker.

The converter is a 120v appliance with a three prong plug and that ground prong touches the receptacle wire's own bare copper that goes back to the power centre's metal case (which is grounded to the frame)

The converter has its own metal case (chassis) with an external ground lug that should be wired to the frame separately (ie not via the converter's 12v neg output) with a wire (gauge is in the installation manual for the converter) if it is a deck mount converter away from the power centre.

If the converter is with the power centre, the converter's metal chassis is touching the (already grounded) power centre's metal case, so you don't need to wire up the converter's chassis ground.

The battery and 12v systems are also negative grounded to the rig's frame, so 120v and 12v both share that ground.

The process of converting power inside the converter chassis will develop RFI type noise that may get distributed down the external wiring. It is always a good idea to locally ground the chassis of these type of unit.

My PD9260C has a external ground lug installed which I ran a solid copper wire from there to the closes frame ground location.



Roy Ken

Thanks Westend. The connection to the copper gas line was done years ago at the Palomino factory during initial construction.

The converter 120 AC should be grounded through the ground wire in the supply wiring. If you wish to ground the chassis separately there is nothing bad about that but the chassis of the converter and the circuits are all connected inside the converter to supply ground.
I also commented in your other thread about using copper pipes as a ground plane, not best practices.
You should establish a new ground point for your electrical service.