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Old 09-01-2004, 06:19 AM   #1
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Wiring to the ground ?

Hi there ,
After 2 monthes, in Campgrounds, the holiday season is finished...
the weather was not good , particulary near my home, in the north of FRANCE, where I've decided to live in my A/S and work in the same time, during summer. So what a stormy weather and people and i, wondered if the caravan has to be in contact with the earth ground with a wire or a cable, just in case of the storm flashed me...

Do you plug the caravan to the ground ?
Is there an original cable on genuine A/S to put on the ground , how it was and what to do; may be these complete the electrical wiring, to run well ?

just tell me what to do to secure the caravan.

Thank you by advance.

Bruno.
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Old 09-01-2004, 06:32 AM   #2
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bruno

yes and no

your trailer should be grounded through the electrical service. knowing that you use a transformer in europe to convert 220v to 110v, may create additional connections to earth.

you can add a ground wire from the frame of the trailer to a driven ground rod if you plan on leaving the trailer in one place for a long time.

this would help protect your step down transformer from lightning by providing a direct path to ground instead of having to travel thruough the transformer.

you can accomplish this simply by driving an 8 foot ground rod straight down and attaching it to the frame of the trailer with #4 awg wire (about 1/4 inch diameter wire). clamp the other end to the trailer frame, clean the connection point to bare shiney metal and use a non corrosive clamp such as bronze or stainless steel.

good luck with your project.

john
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Old 09-01-2004, 09:48 AM   #3
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John, good answers!

I'd like to point out that most trailers are properly grounded when the tongue jack is solidly 'grounded' to the ground surface. However, most of us install a non-metallic object between the turf and the tongue jack that prevents proper grounding.

John, the solution you mention is a good solution to what a lot of us do. I, however, use the Airstream tongue jack plate that is made from aluminum and completes the grounding process through the tongue jack.

Rick
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Old 09-01-2004, 12:53 PM   #4
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Not such a good ground

Rick,
The jack post/pad is not a reliable grounding mechanism for a variety of reasons. The first is that the path from the trailer 120v electrical system ground, to the trailer frame, to the jack to earth is typically not electrically solid. The connection points between the jack and the frame tend to corrode over time which causes there to be some resistance and the connection between the frame and the trailer 120v ground point can also develop rust or corrosion. In many campgrounds, the area under that jack is either asphalt, concrete or loose gravel which effectively INSULATE the jack from any potential earth (ie damp dirt) contact.

Although most of us don't do it (me included and I know better), a 1/2' copper rod should be driven into the ground at least a foot or so (watered regularly to ensure contact) and attached to the trailer 120V ground connection located at the circuit breaker box. A/S does attach wiring from this connection to the frame, but again, the state of that connection varies as the trailer ages and is exposed to weathering. On later model A/Ss, there is a wiring lug strip where the 12v negative, the 120V earth ground, the connection to the frame along with the wire to the 120v circuit breaker box earth ground are joined together. There are typically additional openings in the lug strip where you can install another wire which could be run to the outside for connecting to a true earth ground.

Depending on campground power for earth ground is at best iffy. If you can measure ANY voltage potential between neutral and ground with a digital multimeter, that means that the ground connection is NOT truly grounded (something I find at LOTS of campgrounds). A few millivolts is normal, but when you find more than a few volts, then the earth ground connection is faulty within the park power.

On the matter of lighting protection, I installed both a 12v and a separate 120V surge protection device mainly to protect the electronics in our rig. There is a strong potential in any campground for lighting based surges to occur was most of the wiring is underground and if lighting hits a tree it induces a current in any nearby wiring as it travels into the ground, which results in a surge of voltage. Wish A/S would install such protection as factory especially since the new units have quite a bit of electronic equipment on board.

David
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Old 09-01-2004, 01:59 PM   #5
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David

Your analysis of the scenario we all face is correct; the grounding process is not as good as it could be both in terms of its capability ("the state of that connection varies as the trailer ages and is exposed to weathering") and its inherent design because of the traveling mode of our trailers. If we all parked our trailers (now, that would be painful), then the proper method of installing a metal ground spike, as you deftly point out, could and should be done.

Thank you for adding a measure of reality to the discussion.

Rick
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Old 03-01-2010, 05:39 PM   #6
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Reviving this very helpful 5 1/2 year old thread on grounding the trailer; with a question. I am running new 12v wiring for my rear LED turn/stop signals. When I ground the 12v tester to my TV, and test the new trailer wiring, everything lights up when and as it should. When I then move to the back of the Airstream, and try to find a good ground and test the same wires while grounding to the Airstream, no lights. I touch different grounding points, even the frame, and still no lights, nothing. I might add the trailer is not hooked up to the TV, and the front tongue jack is not touching the floor. Not any other object on the trailer is touching the ground (floor) except the tires. I am thinking this has been my 12v issue all along; the trailer is just not grounded anywhere. Could it be this simple?
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Old 03-01-2010, 06:33 PM   #7
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A 1 foot square steel plate buried 1 foot or more underground makes a good ground too. This is up to code, same as a rod driven into the ground.

Check your water pipe connection. If the pipe is metal, copper or galvanized, it will make an ideal ground. Just clamp a wire to it. I think most places these days use plastic pipe, too bad.
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Old 03-01-2010, 06:59 PM   #8
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Ganaraska:
All helpful, but let me add that I am currently indoors on a concrete floor. I am thinking I should attach the trailer to the TV, and drop one of the chains from the trailer to the floor. I must have enough 12v ground by then I would hope.
-Tim
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Old 03-01-2010, 07:11 PM   #9
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Quote:
Originally Posted by ts8501 View Post
Reviving this very helpful 5 1/2 year old thread on grounding the trailer; with a question. I am running new 12v wiring for my rear LED turn/stop signals. When I ground the 12v tester to my TV, and test the new trailer wiring, everything lights up when and as it should. When I then move to the back of the Airstream, and try to find a good ground and test the same wires while grounding to the Airstream, no lights. I touch different grounding points, even the frame, and still no lights, nothing. I might add the trailer is not hooked up to the TV, and the front tongue jack is not touching the floor. Not any other object on the trailer is touching the ground (floor) except the tires. I am thinking this has been my 12v issue all along; the trailer is just not grounded anywhere. Could it be this simple?
This thread, and all the other posts relate to grounding the entire trailer to the (literal) ground. This has more to do with safety when dealing with alternating current and mitigating any dangers/damage from electrical surges.

The "ground" for 12 volt systems, what you are looking for, is a commonly used term that is something of a misnomer. What you are seeking is actually a path to the negative connection of your battery (& converter). When systems are referred to as 12 volt negative ground (earth for you British car fans) it means that a positive connection is established with a dedicated connection via wiring of some kind. Negative connections do not require a dedicated connection since the frame and shell have connections to the negative battery connection. This simplifies wiring because all devices share the same connection, behaving like grounding.

If you are getting nothing at the back of the trailer, are you connecting to clean metal for the "ground" connection? Remember, this is connection to the negative battery post, not the earth. That you are having success at the front of the trailer makes me suspect that this is not your problem. Are you sure that you are getting power (a 12 volt positive connection)?
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Old 03-01-2010, 08:03 PM   #10
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OK are you are trying to test your Airstream turn/stop/running lights ??

They work from the TV through your 7 way plug so if you had the TV unplugged they would not work.

I think you would get better response if you start a new thread since this one is all about grounding for protection from lightning during storms.
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Old 03-01-2010, 08:45 PM   #11
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A lot of confusion here!

The 12 volt DC system is a 2 wire system, it has a positive and negative side. In most modern systems it is the Negative side that is commonly called "GROUND". This does not mean that the system is connected to EARTH ground. It is only a term used by the manufacturer of the trailers and tow vehicles to define one part of the circuit. It may be connected to EARTH ground through your trailer. But it is not a SAFETY circuit.

ON THE OTHER HAND! The ground wire in the AC (alternating current) side of the electrical system is a SAFETY device. It is part of a 3 wire system. One BLACK wire; 1 WHITE wire; 1 BARE wire. The Black wire is the "HOT" leg; The White wire is the NEUTRAL; and the Bare wire is EARTH GROUND.
If your trailer or the outlet it is plugged in to is not wired correctly, the frame and skin of the trailer could become HOT.

Most new AC electrical devices have at least 3 screws, 1 or 2 gold screws; 1 or 2 silver screws; and 1 green screw. The black wire(s) connects to the gold screws; the white wire(s) connects to the silver screws and the bare wire connects to the green screw. If they don't have screws they will have wires and the colors should be matched accordingly for these devices to be wired correctly.

In my opinion the neutral wire should not be connected to the trailer frame or skin in any way. This way if the outlet that you plug into is wired wrong, the trailer frame and skin will not be hot.

The ground wire should be connected to the trailer frame and skin to provide a safety mechanism. Should any AC wire that is hot, come in contact with the trailer frame or skin. If the trailer is properly connected to EARTH ground and there is an electrical fault that causes the trailer frame or skin to become hot, the AC current will take the path of least resistance via the ground wire and not through you, if you are touching the trailer.

The AC ground system is absolutely worthless if it is not connected properly to EARTH ground. The only safe method, is to use a ground plate buried in the ground, or a ground rod driven in the ground.

Do not fool yourself by thinking that the tongue jack is a proper grounding device! YOUR LIFE COULD DEPEND ON IT!
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Old 03-01-2010, 09:09 PM   #12
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Quote:
Originally Posted by TG Twinkie View Post
The 12 volt DC system is a 2 wire system, it has a positive and negative side. In most modern systems it is the Negative side that is commonly called "GROUND". This does not mean that the system is connected to EARTH ground. It is only a term used by the manufacturer of the trailers and tow vehicles to define one part of the circuit. It may be connected to EARTH ground through your trailer. But it is not a SAFETY circuit.
Agreed. That's why I put "ground" in quotes when referring to the 12 volt DC system
Quote:
Originally Posted by TG Twinkie View Post
ON THE OTHER HAND! The ground wire in the AC (alternating current) side of the electrical system is a SAFETY device. It is part of a 3 wire system. One BLACK wire; 1 WHITE wire; 1 BARE wire. The Black wire is the "HOT" leg; The White wire is the NEUTRAL; and the Bare wire is EARTH GROUND.
If your trailer or the outlet it is plugged in to is not wired correctly, the frame and skin of the trailer could become HOT.

Most new AC electrical devices have at least 3 screws, 1 or 2 gold screws; 1 or 2 silver screws; and 1 green screw. The black wire(s) connects to the gold screws; the white wire(s) connects to the silver screws and the bare wire connects to the green screw. If they don't have screws they will have wires and the colors should be matched accordingly for these devices to be wired correctly.

In my opinion the neutral wire should not be connected to the trailer frame or skin in any way. This way if the outlet that you plug into is wired wrong, the trailer frame and skin will not be hot.

The ground wire should be connected to the trailer frame and skin to provide a safety mechanism. Should any AC wire that is hot, come in contact with the trailer frame or skin. If the trailer is properly connected to EARTH ground and there is an electrical fault that causes the trailer frame or skin to become hot, the AC current will take the path of least resistance via the ground wire and not through you, if you are touching the trailer.

The AC ground system is absolutely worthless if it is not connected properly to EARTH ground. The only safe method, is to use a ground plate buried in the ground, or a ground rod driven in the ground.

Do not fool yourself by thinking that the tongue jack is a proper grounding device! YOUR LIFE COULD DEPEND ON IT!
Again, agreed. Proper safety with the AC electrical system is imperative!

The AC and DC systems are different.

Garry's suggestion about starting a new thread is a good idea, too.
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Old 03-02-2010, 08:50 AM   #13
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to ts8501

Let me get this straight.
You have no tail or marker lights that work unless you connect one wire of your tester to the frame of the tow vehicle and the other to a light or wire on the trailer?
When you say "everything lights up as it should". Do all of the lights come on?
Do you have your trailer plugged into your TV?
Your trailer is not hooked to the hitch on your TV.
Sounds to me like you ar missing the negative side of your circuit.
You ran new wires for the tail lights and new wires for the marker lights and new wires for the turn signals?
Do you have a 7 pin plug for your trailer wiring? If so, there should be 1 wire in that connector on the TV side that is connected to the frame of your TV. There should also be one wire one the trailer side connected to the frame of the trailer. When the connectors are plugged together, this is what complets the negative side of the circuit.
Try this. Connect a wire (a jumper) directly from the frame of the TV to the frame of the trailer. This is only a test to determine if you have a completed negative half of the circuit. If you have a set of jumper cables for jump starting a car, you can use it for the "jumper". The handles on the jumper should be red and black. Use the "Black" ones. Make sure the area that you connect to on the TV and trailer are scraped clean, removing any paint or rust.
You will need to have your connector for the TV and trailer plugged together. And the light switch turned on in your TV. The ignition must be on to test the turn signals.
If this works, what it is telling me is that the negative side of the circuit is not completed through your connector. Some people use the hitch to connect the negative side of the TV and trailer. This is not a good practice and can cause all of the lights on you trailer to blink when you are on rough roads.
The negative side of the circuit on both the TV and trailer should be connected through the 7 pin connector.
Let me know what happens.
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Old 03-03-2010, 06:59 AM   #14
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TG Twinkie:

You have the current set-up correct. When I am back at the trailer on Saturday, I am going to test this out.

-Tim
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