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120 AC twist wire nut melted


ok-rver
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I am struggling with the shore power GFCI at my storage bay tripping when I plug in to it. That will be another post. While researching for a bad connection, I pulled the cover off the J-box between the output of my power cable reel and the start of the house wiring. The wire from the reel is the very thin many wires connected to the 6 or so ~12ga twisted wire bundle that feeds the transfer switch. The black lead, blue plastic nut had melted and fallen into the bottom of the J-box. The cone shaped wire that screws on to the wires (inside the wire nut) was still wrapped around the two conductors. Insulation has gotten hot enough to distort. the wires were rigid from heat.  I was able to feed addition wire into the J-box, cut back the wires to good copper and reattach. I will be coming up with a better connection type before I apply 50 amp to these circuits again. My thermal gun feel apart several months ago.  I will be buying a new better gun and will check many of the connections throughout the MH once I have service again. Also posting about the shore power GFCI which has become a 12 hour search for the tripping source.

The metal J-box would "probably" keep the heat from causing something to catch on fire. At some time, the wires might have come in contact with the metal box, been direct to ground and tripped the breaker. We were on 50 amp for 5 days over the last two weeks and never had an issue. Voltage on my Aladdin display were very close when I looked. 

HRS elec cable burn 1.JPG

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Wire nuts are a poor choice for any connection for your main power cord. All a #12 wire too small, minimum size for 50A power cord is #6 wire.

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I believe the cord reel is #6.  The house wiring has 5 or 6 solid copper wires twisted into a bundle with insulation around all of the wires. they look to be 14 ga or 12 ga for each wire. The bundle should be rated for the 50 amp service.

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Wow, scary picture. I've noticed that whenever I stop by the local auctions there is always an ample number of burned out RV hulks ranging from travel trailers to luxury liners. I have read that about 50% of RV fires are electrical related. 

I worked in the silicon forest for many years. In the industry, most generally, engineering specs prohibit the use of wire nuts on conductors larger than #12 and then only on lighting circuits where the current draw is low. Bolted connectors are available for every wire size, are vibration resistant, and much safe in every respect. After seeing your picture I am going to redo every connection in my RV and eliminate all wire nuts. I also plan on upgrading to arc fault circuit breakers. The technology contained in the circuit breakers represents a truly dramatic increased capability in detecting arc faults and preventing heat generated electrical fires. 

Edited by Gary Cole
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20 hours ago, ok-rver said:

I believe the cord reel is #6.  The house wiring has 5 or 6 solid copper wires twisted into a bundle with insulation around all of the wires. they look to be 14 ga or 12 ga for each wire. The bundle should be rated for the 50 amp service.

Where is this bundle of wires you’re talking about ???  
Are you talking about multiple strands inside a stranded wire (as opposed to solid wire)?

like others said, replace those wire nuts with something better!

cheers

Walter

Edited by wamcneil
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Congratulations on a good find,  and thanks for the picture.

In the picture above It appears to be a connection of two cables of the same size to me.   One has different insulation causing it to appear slightly smaller.

However I don't see any #12 wires except for grounds.     I'm inclined to think the wire nut was never tightened properly.      

Repairs definitely need to be made with better connectors.

 

 

 

 

 

 

 

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On 8/24/2021 at 5:58 AM, wamcneil said:

Where is this bundle of wires you’re talking about ???  
Are you talking about multiple strands inside a stranded wire (as opposed to solid wire)?

like others said, replace those wire nuts with something better!

cheers

Walter

You got me thinking about wire nuts. I didn't realize there were other options. I stumbled on a connector called Wago Nuts. They seem pretty solid however I didn't see any rated above 10AWG. What do you propose for wire as heavy as 6AWG? I am more that interested. 

A nice write up here https://homeefficiencyguide.com/wago-vs-wire-nuts/

 

Regards

Ken

 

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I was following this post but believe the issue was not the wire nuts problem but the wiring at the power source 50 amp pedestal. The OP may have installed a 50 receptacle himself or found a campground with improper wiring. Simply stated both 120V legs were on or in the same phase making the white neutral wire carry a 100 amp loading. When both 120V legs are on different phases and each leg in providing the same amount of power the neutral is carring No current in a 240V properly wired situation. Putting 100 possible amps through a marginal although properly wired connection a fire hazard.

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1 hour ago, jfbolkovatz said:

 Simply stated both 120V legs were on or in the same phase making the white neutral wire carry a 100 amp loading.

I would agree except his white wires appear to be ok.  It's the black wire connection that is burned,  right where the wire nut screws on.

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If one placed both 120 V legs on one side of the circuit breaker the 2P circuit breaker would still trip at its rated amperage , 50 A for example, when overloaded therefore preventing the neutral from being overloaded.  All the breaker sees is the heat generated by its bi metal strip (small frame breakers). Or if it has instantaneous trip capability a fault going to ground. It doesn't know how many wires there are or what size. However the picture shows what is clearly a series fault. A fault which is not going to ground. An inverse time/instantaneous trip, or fuse for that matter, has no capability of detecting a series fault except in a few very limited circumstances. Unfortunately series faults are responsible for the huge preponderance of electrical related fires. There is a new generation of circuit breaker available when as I understand can detect both types of faults. Some even combine GFCI detection. I mentioned that type earlier in the post. Not to familiar with how they work at the moment. 

Edited by Gary Cole
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My terminology of describing the twisted bundle may have misled some of you. This is a butt splice I found at Lowes good for up to 4 ga wire. The wire that is under the screw is the stranded wire coming from the cable reel, the same wire as used in the power cord going to the pedestal. the wire running next to the splice is typical of the red, black, and white used for 50 amp house wiring on my MH. This conductor runs to the transfer switch. The same type of wire runs from the generator to the TS and out of the TS to the house distribution panel for the 50 amp service. There are 5 or so individual copper wires twisted together inside a common insulation jacket. They are in the range of 14 or 12 ga. 14 ga is rated for 15 amps. 5 times 15 is 75 but bundled conductors are derated. Monaco "engineers" did the ground work and said what ever this is, it should be good for 50 amps.

Two issues with using the butt splice shown in the picture. 5/8" heat shrink will NOT slide over the splice. 7/8" fits but it does not shrink enough to be anywhere near tight enough around the individual conductor. With conductors coming out both ends of the splice, the splice becomes very long and would require tight bends in the conductors as they leave the splice to get them to fit in the J-box. Both of these are not good practice. There are connectors similar to the Wago that have parallel entry on the same side with an insulated splice. Most on these high current/voltage connectors have an antioxidant gel that the wire is pushed into under the screw to minimize what happened to the wire nut on my black conductor. They are available on eBay and Amazon. I will try my local electrical supply just to be able to handle the part prior to buying if they have them. I will post pictures and the part number when I buy and install them.

The load shedding system monitors for the two legs coming in to be out of phase to allow 50 amp service, otherwise it limit the current to 30 amp. I have only had the MH about 3 weeks. I would never wire a pedestal as two in-phase legs. The 5 or 6 pedestals we have plugged into have all shown 50 amp service on the load shedding monitor which tells me they were wired correctly, as a 240 system. When correctly wired, the red and black "cancel" each other's current out for which ever leg has the least current. The excess current flows to the neutral bus thru the white. I see 30 amp service on the shedding system when I am plugged into the 20amp GFCI at my storage bay. As the AC is off, I see no need to switch down to 20 amp. Only the black conductor wire nut showed any damage, I believe there was an issue with the tightness of the install or it came loss over time. I am only running thru the 20 amp GFCI until I get screwed splices in place on the three conductors. I hope this clarifies any confusion I may have caused.

HRS white 50amp tisted bundle.JPG

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On 8/29/2021 at 12:07 AM, Gary Cole said:

If one placed both 120 V legs on one side of the circuit breaker the 2P circuit breaker would still trip at its rated amperage , 50 A for example, when overloaded therefore preventing the neutral from being overloaded.  All the breaker sees is the heat generated by its bi metal strip (small frame breakers). Or if it has instantaneous trip capability a fault going to ground. It doesn't know how many wires there are or what size. However the picture shows what is clearly a series fault. A fault which is not going to ground. An inverse time/instantaneous trip, or fuse for that matter, has no capability of detecting a series fault except in a few very limited circumstances. Unfortunately series faults are responsible for the huge preponderance of electrical related fires. There is a new generation of circuit breaker available when as I understand can detect both types of faults. Some even combine GFCI detection. I mentioned that type earlier in the post. Not to familiar with how they work at the moment. 

Incorrect.  The double-pole breaker will allow 50a n EACH leg, so if the legs are in phase, there could be as much as 100a drawn through the neutral.
This is one place where parks and individuals who bypass permits and code inspectors should be held liable, and prosecuted.

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3 hours ago, dl_racing427 said:

Incorrect.  The double-pole breaker will allow 50a n EACH leg, so if the legs are in phase, there could be as much as 100a drawn through the neutral.
This is one place where parks and individuals who bypass permits and code inspectors should be held liable, and prosecuted.

Correct since for 120/240V service the neutral carries the difference of the the 2 hot legs amps. This is why the neutral wire is the same size as the hot wires as the maximum amps is 50A. If the 2 hot wires are connected to the same hot side of the transformer then the neutal can carry 100A and the wiring is not adequate.

The best term for 120/240V service is split phase which is a single phase center taped (neutral) transformer wiring.

120/240V 50A service is single phase but often referred to as each phase, 2 phase etc. Very often misunderstoof.

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Picked these up a Locke Supply in Tulsa OK. They had several sizes and also straight thru connections. With my discount, they were $8 each. Twist nuts are maybe $0.50 to Monaco so you see why they are not used. Ran 19 amps thru a combination of the red and black but all thru the white. Checked temperature with infrared gun and no change. Will pull cover off at a campsite connected to 50 amp service and recheck temperatures in the near future. I am comfortable with the new connectors. Middle picture, lower right ports are for wire. Upper left are access to the set screws. These had Allen set screws and made it very easy to tighten. It was a bit tight getting the 6 ga stranded wire into the 4 ga hole in clamp.

HRS elec con 69.JPG

HRS elec con 67.JPG

HRS elec con 65.JPG

My travel electrical bag did not have any copper crimp rings big enough for the ground. I will do that the next time I am in the J-box

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