Let's talk about grounding

[work2much]

As far as I can discern grounding on a camper (or car) is primarily a way to use the frame as a convenient way to reduce wiring back to the battery. My camper came with a battery ground wire which I assume is fastened to the campers aluminum framing structure. As such I have grounded my inverter back to the frame as well. I assume other manufacturers installed components are also grounded to the frame.

In a home grounding is a means to transfer energy to the earth as to release unwanted energy and protect the home and it's electrical components during an unwanted spike such as lightning.

This is my take anyway. Feedback welcome.

Subsequently when I camp I typically lower at least one jack leg to the ground to make minor leveling and add stability. In this process I assume that I am at least partially grounding my camper to the earth. As such I am wondering if it would be good practice to join the solar panels with a common ground wire and attach them as well to the camper frame (or directly to jack leg) to make a lesser path of resistance rather than through my solar controller/battery etc. (solar controller does have fuses between itself and panels and also batteries)

Any thoughts?

[Joe417]

Not sure this is relevant to your question, I've mapped out the complete electrical wiring on my '05 AF 990 to create a wiring schematic and the frame is tied to the negative side of 12 volt power at the left front tie down. But the frame is not used a return for any circuits.

120V ground from the switch box also connects to the front left tie down. In addition there are several other safety ground connections such as the fridge and generator that are tied to the frame.

Not sure if yours is similar but I would think it is.

However, every 12v circuit our camper has a copper return wire. Including all running, signal, and marker lights. I found no electrical circuits utilizing the frame as a return.

[bigfootford]

Camper negative and shore power earth ground are tied together!

Where? Your Fridge and if you have a hot water tank that is 120vac and propane.

Lot's of discussion back years ago.. If your interested here is a link.

Or just look at the pictures that I produced along with the notes showing the grounding.

You also will notice that the AC ground and DC- are also tied together at or around the converter.

http://www.picturetrail.com/sfx/album/view/16562094

Or if you do not want to go look here is one picture showing the BOND... AC ground to DC-



Not to Hijack this thread but if your interested in the reason I came up with these pictures you can learn from this thread:

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/19726244/srt/pa/pging/1/page/1.cfm

Jim

[HMS_Beagle]

My Bigfoot too has the tie down location grounded (green wire). Everyone's camper is grounded to the truck through the charge/light cable too. The green ground is supposed to be non-current carrying except in a fault situation. The charge cable does not have a green ground. You really only want the green ground connected to the current carrying ground (usually white) in one place. That is to discourage ground loop currents, which can cause all manner of odd behavior. I would not use the camper chassis as a current carrying ground for that reason. It should be tied to green ground so that faults are noticed (12V wears through and touches chassis, raising it to 12V). While 12V is considered SELV voltage by standards, it can cause a fire even if it doesn't electrocute.

[Wardster]

The ground in my NL is attached to one of the tie down locations. As long as the FastGuns are connected, the 12v system is grounded to my truck through the tie-downs.

[AnEv942]

I cant address the lightning strike as in earth ground.
But on the 12v grounding, or 12v negative return, if mounted on truck likely its tied and is chassis grounded (NOT EARTH GROUND). Even unmounted likely chassis grounded, though possibly not designed as such battery negative probably can be be metered to/thru chassis.

most everything I'm aware of has a wired return on anything 12v, not relying on chassis-but frame is connected to battery negative. One source is the water heater, the other the refrigerator, what or where else unknown. I discovered this on ours hooking up light by door, routing ground wire behind screen door frame and light came on. Always assumed camper frame isolated on the 12v. Nothing you want to rely on, negative returns should be wired, though I utilize for the CB. But I'd meter if you think the frame isnt tied to battery.

[deltabravo]

Truck campers are a different beast with regard to 12v negative connections. I don't believe there is a connection between battery negative and the chassis of the camper, since all of the metal in one (Arctic Fox) is in the walls. Unlike a travel trailer, a camper really doesn't have a "chassis grounding system"

[HMS_Beagle]

Sailboat lightening strikes illuminate how random and chaotic lightening is. USBoat keeps some statistics on this, just as many grounded masts are struck as ungrounded, the same story for static dissipators. Damage ranges from very little, to complete loss of all electrical equipment, to hundreds of holes blown in the hull and sinking.

In a camper, pobably the best thing is to park close (but not too close) to something a lot taller. A jack lowered to the ground is probably a decent ground for a lightening strike (short air gaps are no trouble for lightening), but getting the 100,000 amps or so to go from the frame on your solar panels to the jack is not an easy thing.

[burningman]

work2much wrote:
If lightning were to strike the solar panels on an rv what would be the likely outcome?

Fully charged batteries 🙂

[towpro]

Ground does not attract lightning, it blends off the positive static potential. It's this positive potential that attracts lightning. Remember the electron it attracted to the protron

[wgriswold]

work2much wrote:


This makes sense. I guess a simpler question would be, is there any concern or way to protect the camper from lightning strikes? If lightning were to strike the solar panels on an rv what would be the likely outcome?

Your question is one that is often asked in regard to sailboats. One school of thought points out that grounding the mast to the sea makes the mast the highest ground and attracts lightning. The other suggests that providing a path to ground protects the boat. I don't know which is right.

I do know that it is much easier to ground the mast by making a connection to the sea. A good ground to earth on land is much more difficult. I have heard that it would require a rod sunk to a depth of 6 feet in the ground. I don't know about that but I suspect that it is hard to get a good ground while camping.

[work2much]

wgriswold wrote:
I think there is a problem with semantics. Our 12v systems are not grounded, that is connected to earth ground. The "ground" is actually the negative side of the +/- 12 volt system. You are right, the frame is used as the return wire to the 12V battery. A ground is not necessary because the 12V system presents no danger to us. That is why we can touch both posts of a battery with no harm. Higher voltage direct current systems are grounded to earth ground with a third wire for safety.

120V systems are grounded to earth for safety reasons.

I believe that we should not use ground as a description for the negative part of the 12V system because it leads to confusion with earth ground. I acknowledge that it is hopeless to change that.

This makes sense. I guess a simpler question would be, is there any concern or way to protect the camper from lightning strikes? If lightning were to strike the solar panels on an rv what would be the likely outcome?

[wgriswold]

I think there is a problem with semantics. Our 12v systems are not grounded, that is connected to earth ground. The "ground" is actually the negative side of the +/- 12 volt system. You are right, the frame is used as the return wire to the 12V battery. A ground is not necessary because the 12V system presents no danger to us. That is why we can touch both posts of a battery with no harm. Higher voltage direct current systems are grounded to earth ground with a third wire for safety.

120V systems are grounded to earth for safety reasons.

I believe that we should not use ground as a description for the negative part of the 12V system because it leads to confusion with earth ground. I acknowledge that it is hopeless to change that.

[time2roll]

For 12v power ground is just a convenience.

For 120v power think of hot as the source and neutral as the drain. Ground is the secondary drain that provides a path during a fault so the power does not go through you as a drain.

Nothing is really going to earth ground especially with an inverter. If you are plugged in the ground connection is all you need.

Technically the frame of the panels should be grounded to the RV frame same as a home installation but few do it. More important if you have a series high voltage system.

If you want to conduct a direct lightening strike that would take a bit more effort. The strike will still jump to the earth and you should be unaffected.

[work2much]

jimh425 wrote:
I don't think putting the leg down will make any difference.

As far as making the camper more conductive to lightning? You're probably right. Being that the solar panels are directly overhead while sleeping I guess I was looking for a little piece of mind. I never could sleep through lightning storms in the camper.