Pics of fuse boxes/wiring...please post

[asianflava]

1) Yes

2) Yes

3) When the trailer and vehicle are hitched, Yes

4) Yes, you ground it anywhere to the metal. Typically near the battery.

5) When the trailer and vehicle are hitched, Yes

6) You can do this, if the structure is wood, you will have to.

7) The main reason to ground the battery to the frame is fewer wires. For example; You have to hook up a light in a car, you only have to run the positive wire. The negative is made where the base screws into the sheetmetal. In fiberglass cars and wooden teardrops, you don't have this luxury. You will have to run the negative wire, not necessarily back to the battery, but at least to a common negative bus (frame).

[Dee Bee]

1) Yes

2) Yes

3) When the trailer and vehicle are hitched, Yes

4) Yes, you ground it anywhere to the metal. Typically near the battery.

5) When the trailer and vehicle are hitched, Yes

6) You can do this, if the structure is wood, you will have to.

7) The main reason to ground the battery to the frame is fewer wires. For example; You have to hook up a light in a car, you only have to run the positive wire. The negative is made where the base screws into the sheetmetal. In fiberglass cars and wooden teardrops, you don't have this luxury. You will have to run the negative wire, not necessarily back to the battery, but at least to a common negative bus (frame).

SO in response to #7...If the frame is not used to complete the circuit in a fiberglass or wooden tear, why ground the battery to the frame for the cabin/galley "house" light system, since all these cuircuits are hard wired to that battery?
What is the electrical reason for doing so?

Thanks for the info I don't want to have a flaming experience!

DEE

[Scooter]

On a HF bolt-together trailer, grounding to the frame assumes each and every bolt makes positive connection...otherwise, problems. Something to think about.

[TonyCooper]

This is what I came up with. Parts all came from my local Home Depot and AutZone. About $15 or so. I am not planning to ground my trailer battery to the trailer chassis.

http://home.earthlink.net/~tony.cooper/TDProj/page9.htm

Tony

[Jerry Lawrence]

Just a note, and I don't know why: Originally my trailer battery and 12V wiring was NOT grounded to the trailer frame. I have no 120VAC wiring. The trailer running and brake lights used a standard 4 pin plug. My truck was factory wired with a 4 pin plug. The first time I hooked up the truck to the trailer for a light check, the turn signals, tail lights and brake lights were acting crazy. Could not figure it out, checked all the wiring several times for shorts, etc. Finally I grounded the trailer 12V circuit to the frame, and all was well.

-Jerry in San Juan

[bdosborn]

SO in response to #7...If the frame is not used to complete the circuit in a fiberglass or wooden tear, why ground the battery to the frame for the cabin/galley "house" light system, since all these cuircuits are hard wired to that battery?
What is the electrical reason for doing so?

Thanks for the info I don't want to have a flaming experience!

DEE

Here's what it says in the NEC handbook (which has interpretations of the NEC):

"The AC equipment grounding conductor may not have sufficient ampacity to safely conduct the DC fault current. This will necessitate installation of the battery bonding conductor."

So if the battery where to short to the frame while the frame is grounded via a 120v shore power circuit, the AC ground might not conduct the fault without burning out. If the battery is grounded to the frame, then the frame can conduct a DC fault to the negative terminal of the battery.
Bruce

[shil]

Well, I've got no 120 volt wiring to worry about, so I won't (worry).

I'm not using the frame as a common ground for any house wiring, so the convenience argument falls away.

The house wiring is no where near the frame; where it is it's run through conduit.

If the only reason to ground the battery to the frame is in case of a short to the frame, one could argue that it's safer not to ground the frame: no ground means no short circuit.

The frame IS grounded to the car. It seams wackier to me (not sure why, it just does) to ground the house battery to the car, I'm trying to keep things separated.

Of course, I may be wrong.

[bdosborn]

If the only reason to ground the battery to the frame is in case of a short to the frame, one could argue that it's safer not to ground the frame: no ground means no short circuit.

The frame IS grounded to the car. It seams wackier to me (not sure why, it just does) to ground the house battery to the car, I'm trying to keep things separated.

I would rather ground the frame so that I don't ever risk having an energized hunk of metal waiting to short to ground through me. Of course, it is only 12V dc and I've touched the positive terminal of start batteries all the time and I'm still around. So, yeah, its probablly not that big of deal if you don't have 120v shore power.

I would definately want the frame and battery grounded to the tow vehicle with a better ground than a greasy ball and hitch. As was reported in an earlier post, weird things happen when you have a poor ground. And if your going to charge the battery from the tow vehicle, then a grounded frame and battery makes a lot of sense.

I guess there's not a hard and fast rule here. For me, its just one more bit of wire that I'd rather put in now instead of later because I've got weird electrical problems that I can't trace.
Bruce

[Chuck Craven]

I have seen this comment sever times “it’s only 12 volts”. Batteries in shorted condition put out over 1000 amps even the little ones. That is why they start fires or explode.
Fires and exploding is very rare. Most likely what will happen is you will get a ring or a watchband in contact with the + and – of the battery and melt them in to your hide.
Then a trip to the hospital, to get it removed. I had a friend that was working on his 40 Ford, put his hand up under the dash to remove a panel light. He got the watchband across the amp meter and ground. After a few minutes managed to break it loose. Went to the hospital to get the watch removed. It took several months before they could tell if he had damaged any tendons. He had a scar that went all around his wrist that looked like a twist-o-flex watchband. They call that branding in Texas, if you are a cow. Even the 12v from a power supply or battery charger can do you damage. It’s the current that kills not the voltage. As for grounding of the frame to the – side of the battery or power supply is required not for the electrical circuit but for static electricity discharging when driving down the road. It is a large surface to help discharge the static electricity generated from the rubber tires. It also helps if every thing is at the same potential. If your camper is struck by lighting then you will be better protected if the wiring and chassis are all tied together. It doesn’t mean that anything won’t get damaged but you will be better protected. A direct hit from lighting and all bets are off. If the chassis and the wiring are all tied together, grounded through your trailer jacks the chance of static electricity build up on the trailer is much lower and the lighting will look for some thing the is charged up like a tree.
Chuck

[bdosborn]

Even the 12v from a power supply or battery charger can do you damage. It’s the current that kills not the voltage
Chuck

Yes, its current, irrespective of voltage that kills. As little as 5mA can induce ventricular fibrillation (a heart attack) after 3 seconds, assuming the current has a path through your heart. Luckily, the human body is a pretty good resistor. If I measure the resistance of my body by holding the leads of a sensitive ohmmeter and I have clean dry hands, I measure a resistance of about 1 million ohms. So at 12v DC how much current would be conducted through my heart if I grab the terminals of a battery?

Ohms Law
E=IR
I=E/R
I=12/1,000,000
I=1.2 x10^-5 or 12 microamps

Roughly 3 orders of magnitude lower than what is considered lethal.

Now lets assume I've been working really hard on my teardrop and my hands are good and sweaty. Now I can measure a resistance of 17,000 ohms.

I=12/17,000
I=7X10^-4 or 700 microamps

Now we're only about one order of magnitude below the lethal level.

Now don't get me wrong here, you have to be carefull working around electricity. Period. But there is a reason that we use 12V batteries for systems like start batteries and power for a teardrop; its a pretty rare circumstance that causes an electrocution death. And as Chuck described, there's a good reason for a fuse in every circuit (see previous post with the oneline diagram) and taking off all your jewelry when working on energized circuits. You might not be electrocuted but how many of us have accidentally touched a wrench across the terminals of their car battery?
Bruce

[Arne]

The reason trailer lights act crazy when there is a bad ground to the tow vehicle is the lighting system attemps to use one of the other light wires as a ground.... for instance, you put the brakes on and they are high draw, so the system might try and use the runing lights as the ground and the results can be weird.

I used to use a 3 wire household plug for the trailer, and until all the rust got worn off the ball, I got static in the radio as the lights flickered off and on and the lights were wierd. That was with a fixed hitch on the car.

With a removable receiver, it is even worse as the reiver and ball bracket both get rusty and there is never a good contact... so I have gone to a conventional 4 wire hookup.

[Ron Dickey]

The above answers have some very good pictures of what one should look fore.