Grounds for confusion

[WDavidG]

Working on mods to my electrical system (2014 scamp 13) led me to study it more than I had previously. Am I correct that scamp does not use a chassis/frame ground for the DC negative for anything (possible exception of brakes though Scamp's electrical diagram doesn't so indicate)?

Second and larger question is about the other sort of "grounding", equivalent of the green ground wire in an AC circuit. My scamp-installed Progressive Dynamics converter specifies that it be grounded to the chassis (in addition to the + and - battery connections). Many other devices, including most inverters, carry similar instructions. I just discovered that my converter was not grounded by Scamp. Was this just a one-off error, a bad day at the Scamp factory, or is it common to ignore the ground? For safety reasons I would have thought that some electrical code for the RV industry might dictate procedure. In any event I assume I should remedy the issue.

[floyd]

Originally Posted by WDavidG

Working on mods to my electrical system (2014 scamp 13) led me to study it more than I had previously. Am I correct that scamp does not use a chassis/frame ground for the DC negative for anything (possible exception of brakes though Scamp's electrical diagram doesn't so indicate)?

Second and larger question is about the other sort of "grounding", equivalent of the green ground wire in an AC circuit. My scamp-installed Progressive Dynamics converter specifies that it be grounded to the chassis (in addition to the + and - battery connections). Many other devices, including most inverters, carry similar instructions. I just discovered that my converter was not grounded by Scamp. Was this just a one-off error, a bad day at the Scamp factory, or is it common to ignore the ground? For safety reasons I would have thought that some electrical code for the RV industry might dictate procedure. In any event I assume I should remedy the issue.

When on shorepower the 110V power is grounded through the cord. (Think of the Scamp as an appliance)
The frame on the Scamp is not profoundly grounded , even with the tongue jack and stabilizers down.


The 12V house power is grounded back to the source (negative battery post)

The brakes (12V) use the frame as a ground back to the TV ground(return). Could just as well use wire, but the frame is convenient and works well.


DOT lighting ground wires are wired through the interior of the trailer and so run wiring back to ground of the TV. (better than attaching to the frame as it is hard wired and protected from corrosion.


The body of a Scamp is non-conductive fiberglass , a 110V ground wire to the frame would not be effective at any rate.Stab and tongue jacks often offer less of a ground than a person touching the frame.

[steve dunham]

The green wire in the 120 VAC service cord is the equipment grounding conductor and under normal conditions is not a current carrying conductor
The green wire is connected to the panel and the ground bus in the trailers service panel ( It is isolated from the white or neutral conductor)
The metal frame of the trailer is bonded to the equipment grounding conductor
By intentionally grounding / bonding the frame , if the frame becomes energized this low resistance path to ground will carry the current and activate the overcurrent device. ( Breaker trips / fuse blows )
If the frame is not intentionally and effectively grounded , if the frame becomes energized and you , standing on the ground touch the frame then you become the current path to ground
If the receptacles in the campgrounds pedestal were all GFCI protected that would solve some problems and create others
A generator that is not intentionally grounded ( IE : Driven Ground Rod) is a floating system or not referenced to ground or a separately derived system and there is no potential / voltage to ground
The code cannot determine if you are connected to a campground pedestal or a generator so the assumption is you are connected to utility power / pedestal which is intentionally and effectively grounded

The reasoning that by bonding / grounding the metal trailer frame to the equipment grounding conductor you are creating a hazard is not factual
Bonding / connecting the neutral ( Grounded ) conductor to the frame does introduce a hazard
Connecting neutrals and equipment grounds together in the trailers service panel also introduces a possible shock hazard .

[floyd]

Just a note...
Steve is a bonafide expert in the field of high voltage AC electrical.
you can certainly believe that his responses to questions in his field will be well thought out and accurate.


12V DC/ DOT wiring is different and in many ways is a different expertise.
Although RVs often use and interface AC and DC/DOT, It must be noted that they still involve many different principles of operation and different solutions.

[WDavidG]

Originally Posted by steve dunham

The reasoning that by bonding / grounding the metal trailer frame to the equipment grounding conductor you are creating a hazard is not factual
Bonding / connecting the neutral ( Grounded ) conductor to the frame does introduce a hazard
.

Thanks Steve and Floyd for the helpful answers. Steve: to be clear on your information, I assume that you do recommend that I add a connection from my converter's grounding lug to the trailer frame as indicated in PD's manual and contrary to Scamp's installation. Correct?