shocked - Fiberglass RV


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Old 08-28-2013, 07:59 PM   #1
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Smile shocked

I was installing a vent for refridgerator . I had the trrailer pluged in. threw the hole in the side I accidently touched the copper line going to the stove and got a shock . I also got a shock from the ground wire coming down from the electic box to the frame. I have checked all electric receptles one on the out side and one on the sink , took apart the electric cord to make sure they were in phase. had the cover off the box looks like everything is hooked up right just wonder if I have a bad electrical box. need help
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Old 08-28-2013, 08:23 PM   #2
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Yikes!!!

Okay - Ill give you the long version ---

It sure sounds like your ground wire is hot, which suggests that it is making contact somewhere with a live wire. At the risk of stating the obvious - this is a potentially dangerous. situation. Unplug your trailer from its power source now, if you have not already done so.

I'm guessing you are at home with your 110v circuit plugged into a home outlet? The problem could be with the home circuit, the trailer wiring, or even any appliances with a grounded plug that you might have plugged into the trailer.

I would start by taking a careful look at that electrical box - the one in the trailer. Has a screw or something else metallic fallen into it and created a bridge between the black 110v wire and the ground circuit?

I suggest you acquire a voltage tester. Plug one terminal into the live pole of the 110v outlet that the trailer power cord is plugged into (black wire/shorter slot for the plug in newer outlets) and the other into the ground hole and see what kind of resistance (ohms) reading you get. It should be infinitely high. If it is not - then the problem is the circuit coming from the house (if that is the case you might consider calling an electrician). DO THIS WITH THE POWER TO THE OUTLET OFF. Low resistance means that there is communication between the two circuits - a short.

If it is good, then move onto the trailer power cord. Those power cords take a lot of abuse. Unplug the cable on both ends and then test it by measuring the resistance between a live pole (black wire) and a ground pole (green wire), on either end of the cable - doesn't matter which end you pick. If the resistance is low the cord has a short in it - replace it.

If the power cord is good, then it check a trailer outlet just like you checked the outlet coming from your house. If you see low resistance between the live pole and the ground pole, start by unplugging all appliances - one at a time - and see if that makes a difference (fridge, A/C, 110v light, etc). If it does - you have pin pointed your problem. The appliance or its cord is bad.

If you are still seeing a short at one of the outlets after all appliances are unplugged, then it is in one of the trailer's circuits and you'll probably have to rewire them. If there is more than one circuit you could isolate the problem by disconnecting one circuit from the trailer's circuit box (with the main power cord unlugged, of course!). Plug the main cord back in and check the outlet of the circuit that is still wired up. If it is okay - the problem is in the disconnected circuit. If not, it is in the still connected one. (If there are more than 2 circuits you'll have to disconnect them one at a time, checking the still connected ones at each step.)

If you decide to give this a whirl - remeber that the power should always be off & you'll be safe. Good luck!
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Old 08-28-2013, 08:43 PM   #3
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First off, if you have a propane tank hooked up, shut it off, and pull power immediately. That's your gas line that's electrified.

After that, time to look down that line and see where a wire is rubbing.

I had this happen in my house. After ripping out much drywall, I found the idiots ran a screw in the pex water line (Murphy), which was right above an illegal wire connection in the wall (Murphyx2), which was above my gas line (Murphy hates me). The slight water leak in the wall ran down the wire, down the stud, and to the gas line. I found out it was hot when I nearly peed myself when I touched that thing, while working on something else.
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Old 08-30-2013, 08:08 AM   #4
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hi everyone thanks for all the informative replies I FOUND the problem a wire going to the flouresent light over the sink had worn threw the insulation at the point where it went into the metal light case the ground wire for the light was reveted to the case 40 years of the coach moving wore the wire insulation causing My problem
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Old 08-30-2013, 10:57 AM   #5
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I think you still have a problem. Being connected to shore power should connect your frame to the household ground. Any fault in the trailer, like what you have described, should cause a breaker to open. There should never be a difference of potential between the frame and ground. You found what energized the frame but not why the breaker did not open. You need to correct this. Raz
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Old 08-30-2013, 10:05 PM   #6
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If I recall, there was only a 2 conducter wire going up to the flourescent light on mine, like a cheap extension cord. The metal there would be separated from the rest of the trailer by the fiberglass. The concept of "floating ground" comes to mind.

Nice to find another boler American owner here Charles. What part of MI are you from? We travel that way on occasion. Not often enough to see all our friends there though.
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Old 08-31-2013, 06:33 AM   #7
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Originally Posted by Roy in TO View Post
If I recall, there was only a 2 conducter wire going up to the flourescent light on mine, like a cheap extension cord. The metal there would be separated from the rest of the trailer by the fiberglass. The concept of "floating ground" comes to mind..

Roy, I'm an EE so I understand the concept of floating ground and the reasons one might want to do it. This is not one of them. If Charles got a shock from the plumbing and from the ground pin on the electrical box, then there is a wiring error. The reason for having the three wire system is to eliminate this from happening. The trailer frame and all metal chassis (fridge, converter, etc.) should be connected to the trailer AC ground and to the house hold/ shore power AC ground when plugged in. There should never be a voltage between the frame and AC ground. By making these connections you eliminate the shock hazard. A simple continuity test can verify this. Be safe, Raz
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Old 08-31-2013, 09:15 PM   #8
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HI ROY were over in the south west part of Michigan Saint joseph exit 28 off of I-94. that short should have tripped the breqker I took it out could not find one too old so I put in whole new breaker and box I have been through the whole electric system on that trailer and now have peace of mind
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Old 08-31-2013, 11:22 PM   #9
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Raz,
The reason I mention floating ground was that I previously had a solar control that was a positive ground, yet they called it a floating ground so I could use it in a -ve ground trailer. Never could get my head around that. It just sounded the same. I really don't understand electricity beyond the basics.

Hey Charles,
Sorry we don't get out that end very often, every few years or so a dog thing comes up in Kalamazoo. There is a really good shop for donuts in the area.

Most of our visits end up on the eastern side; say between Detroit and the Thumb. The Algonac meet sounds great, it just does not seem to fit into our schedule, maybe one year.
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Old 09-01-2013, 07:48 AM   #10
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Ground

Quote:
Originally Posted by P. Raz View Post
I think you still have a problem. Being connected to shore power should connect your frame to the household ground. Any fault in the trailer, like what you have described, should cause a breaker to open. There should never be a difference of potential between the frame and ground. You found what energized the frame but not why the breaker did not open. You need to correct this. Raz
I agree ,but on my Scamp the 12 VDC Neg or ground was bonded to the frame
but the 120 VAC Equipment ground was not . I called Scamp and questioned why the frame and non electrical metal parts of the trailer were not grounded through the supply cord's equipment grounding conductor . Scamp was convinced that grounding the frame was a hazard to life and the trailer was isolated by the tires . Ignorance is bliss
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Old 09-01-2013, 10:57 AM   #11
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I also agree that there is still a problem. If you have an open ground, a fault to the frame or anything bonded to it will cause a shock to the earth (unless you are powered by a generator not earth bonded).

If the frame & the rest of the metal of the trailer are tied to the AC ground, small fault currents are carried by the ground connection, which usually has a much lower resistance than an "earth" connection through your shoes. The low resistance ground connection will cause large faults to trip the supply breaker.

I'd look for an open ground connection, often caused by adapters or cords with broken ground pins.

As to Scamp, I'm surprised that they don't comply with NEC, and that they haven't been hit by a suit.
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Old 09-01-2013, 11:07 AM   #12
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Originally Posted by Jon Vermilye View Post
If the frame & the rest of the metal of the trailer are tied to the AC ground, small fault currents are carried by the ground connection, which usually has a much lower resistance than an "earth" connection through your shoes. The low resistance ground connection will cause large faults to trip the supply breaker.
Thanks Jon,
I know have a better understanding of one of the many mysteries of electricity. I've always wondered how both the 120V and 12V systems could be 'grounded' to the same frame. Brings a whole new meaning to "the path of least resistance" to me.
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Old 09-02-2013, 04:33 AM   #13
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Originally Posted by steve dunham View Post
. Scamp was convinced that grounding the frame was a hazard to life
Hazard to life, I wonder how they came to that conclusion?


Quote:
and the trailer was isolated by the tires .
Unless the stabilizers are down. Raz
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Old 09-02-2013, 09:00 AM   #14
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Hazard to life, I wonder how they came to that conclusion?




Unless the stabilizers are down. Raz
Or the tongue jack is down.
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