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Old 04-06-2013, 03:50 AM   #1
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Yesterday, we had a problem that took a bit of head scratching. My wife plugged in the trailer to the 30A receptacle but nothing worked. No A/C, and no Convertor, but we had voltage. At first it was thought to be the 30A receptacle so it was replaced. That turned out not to be the problem. I checked the circuits, assuming that it was problem with the cabling to the siders. After checking that out, I decided to look at the junction box where the power cable is connected.

When removed the cover, I got a shock from it. As you can see from the attached picture, the neutral wirenut melted. Upon closer inspection, I found that the neutral wire was rubbing against the junction box cover and eventually from the constant vibration, the wire nut wore through and the neutral wire made contact with the junction box lid, grounding the neutral wire.

I made a temporary repair to get us through the night and will properly repair it today.

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Old 04-06-2013, 04:02 AM   #2
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MG looks as though you were very lucky as it could have been a very bad result. Good luck with the repair and as of now we all will probably be looking at our units for a possible problem. Just shows how the people putting these things together care.
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Old 04-06-2013, 04:26 AM   #3
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I'm wondering where the junction box is picking up electricity. If white is neutral, there shouldn't be any coming from that.
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Old 04-06-2013, 06:30 AM   #4
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Looks to me like you had a loosely made neutral connection that heated. Let me guess that when you pulled the cover from the box you got a shock as soon as the cover was free and the melted wirenut was stuck to it. Be it the hot wire or dealing with an open neutral while the hot is still connected, you're still dealing with 120 volts; just pull the plug. Bear in mind that if this was a 4-wire 240 volt trailer, when a neutral opens, you could have anywhere from 0 to 240 volts at any given AC electrical opening.
If you can get your hands on some 3M Schotchlok wire nuts, they tend to stay quite well, but once they go on, you often have to cut them off. What you have there is a great example as to why you need to keep electrical boxes covered; that's what keeps the hazard contained.</span>
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Old 04-06-2013, 09:16 AM   #5
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H2oPumper is right. The neutral caries the unbalanced load and as our units are only 110V, 100% of the load comes back on the neutral.
Quick lesson:
If you have a 240v system like at home. Many circuits share the neutral. So if you have one circuit with a 16 amp load and the other has a 10A load, the neutral will carry 6 Amps. So the neutral can be very dangerous.
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Old 04-06-2013, 04:25 PM   #6
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I should have taken pictures of the finished repair so that you could see what I did.

I had to cut back the ends of both cables and shift the box so that there were sufficient pigtails to make new terminations. Both cable grounds were tied to the box under the samescrew,instead of the original method. This was the method that I was taught as an electrical apprentice. I positioned the phase and neutral wires so that they would be less affected by vibration. I used red wire nuts to finalize the connections and replaced the cover.

In the final analysis, it was vibration the caused the neutral wire to short to ground. The wire nut on the neutral was pressed up against the junction box cover and over the years, the plastic of the wire nut wore through and grounded out. This is a serious failure because circulating currents develop in ground and shorted neutral circuit and can cause excessive heating in the cable. Had the phase wire shorted instead of the neutral wire, the problem would have been apparent immediately by the supply breaker tripping.
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Old 04-06-2013, 05:42 PM   #7
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Exact same thing happened to me in the middle of a trip. I think vibration loosened the connection. I could actually smell the burnt plastic, slightly, from inside the trailer. It was not a good feeling.

I was lucky no fire started. I was able to fix the problem on the road.

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Old 04-07-2013, 12:56 AM   #8
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We don't have our RV yet, but I'm just wondering if on yours is the cord strapped, clamped or supported by anything other than the box connector? If it's just held by that plastic cord fitting, it will turn inside the box knockout and move the connections. Solder is not an connection approved by the electrical code, but it would sure be tempting for me to put a touch of solder about an inch down from the wire tips and still maintain a good copper to copper for the wire nut. Also, tape the wires together for each wire nut. That way when they move, they move together and not independently within the wire nut. Neutrals and grounds are the most important to maintain as they will cause the most damage if they fail; problems in the hot feed are quite obvious since things just don't work. In the meantime, keep covers on and your connections in their boxes.
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Old 04-07-2013, 08:58 AM   #9
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The power cable for the trailer is clamped down to the floor of the trailer with 2 loop clamps. As far as I could tell, pulling out the cable to plug it in, had not affected anything with the box connector. As a matter of fact, thebox connector was a bear toget out, even thoughit was plastic.
I did nottape thewirenuts together but I did use an old linesman trick and wrapped electrical tape around thewirenutand wire in thetightening direct. This prevents the wire nut from loosening.
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Old 04-08-2013, 11:38 AM   #10
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Had the same type of problem in a junction box for one of the slides. Our fireplace (which is a heavy amp user) was on this circuit. We ended up replacing the length of wire that runs between the frame and slide junction boxes as it had melted about 6 inches. We also opened every other junction box to check the wire nuts and re-tape all the nuts/wires.
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