Why is my shore power plug melting?

[alien_scones]

While I'm having fun replacing the brakes, the camper is parked in my driveway.

Its plugged into a 25 foot 30 amp extension cord, which is plugged into a 30 amp plug outside the house.

The camper AC is running, almost nonstop. It's 100 degrees outside and the inside AC is set for 80.

The extension cord female end looks even worse.

Suggestions?

Thanks

[Racebug]

bad connection. either male or female end of that plug.

[Brentw]

Connections in ( most likely female side) are not snug enough to the blades. If possible reduce some of your load, fridge/ HWT on to propane.

[jbryant]

Check all connections making sure when you plug in it is tight. Make sure that AC is all that is on. With the camper plug and the extension cord you get less amps. Air and heat cause it to melt as well as excessive amp draw on a long electrical cord.

[sourdough]

Is either plug, or both, loose when they plug in? That sure looks like arcing. How old, worn, are the components? Another thing from the pic; is that an aftermarket 30A cable? What is the gauge of the wire in it? It's been many years since I had a 30A cable in my hand but that sure looks smallish making me wonder if the size of the extension cord is causing an issue. Have you used this same cable before in the same conditions you have now? If so, then it again points back to the connections. Do you have an EMS? If not, you should invest in one - they are a great diagnostic tool.

[JRTJH]

Originally Posted by alien_scones

...
Its plugged into a 25 foot 30 amp extension cord, which is plugged into a 30 amp plug outside the house.

The camper AC is running, almost nonstop. It's 100 degrees outside and the inside AC is set for 80.

The extension cord female end looks even worse.

Suggestions?

Thanks

I think you actually have two issues going on. First "was" (now is) loose, arced connections. The condition of the hot lead in your photo shows arcing and a poor connection. You're going to get a voltage drop across that terminal in the plug which will cause an increased amp load which just makes it deteriorate faster. It will, in the not too distant future, short out and stop working. Whether it's tomorrow or next month is anybody's guess....

Now, the second issue, and probably the root of what started the first issue is the total length of the wiring (shore power cord/extension cord). Your trailer shore power cable is probably 25-30' long and you're using a 30' extension cord. That's roughly a 60' run of 30 amp cable (very near or over the maximum run) with a connector in the middle and one on each end, any or all of which may have that arcing/burned connector. With the starting load of a typical RV air conditioner in hot weather, you're probably loading the cable with more demand than it can carry. With the arced terminal, the voltage drop will likely cause an amp load increase that will melt the wiring where it connects to the pin in that plug. I'd suspect that with the air conditioner running that plug is so hot that it would burn your hand if you tried to hold it without a glove.

The fix? Cut that end off the cable and install a "quality" 30 amp replacement plug. Marinco is the brand I use, but there are many other brands that are just as good. Don't buy the $3.99 discount store brand..... It might work, but IMHO, the quality of the pins is such that they just don't last and in a week or two, they will look just like your photo.

Ultimately, try to eliminate the need for the extension cord. If you can park the trailer closer to the outlet, don't use the extension cord. If you can't, then possibly find a 50' power cord so you don't have the "plug in the middle"..... Along with that, try to eliminate all the trailer electrical load that you can. Turn off the electric element on the water heater, run the refrigerator on LPG, and avoid using the microwave with the A/C running. Even though you don't blow the circuit breaker, you're at/very near the maximum 30 amps. Reducing the power consumption will reduce the load through that pin, helping preserve the replacement plug and prevent it from overheating and melting the plastic like this one.

[flybouy]

As many have stated loose connection=arcing=carbon build up=high resistance=higher amp draw=heat=fire. Don't use it, replace with quality plugs and when stripping the wire back for the new plug discard any discolored wire that the heat has effected.

[alien_scones]

Thanks again for all the informative replies.

Should I fill these replacement plugs with dialectic grease or silicone to attempt to waterproof them, or will that only cause them to smoke more/ burn faster when it comes time for these to melt?

[JRTJH]

Using dielectric grease on those screw contacts won't "hurt" but I don't know if it would help either. It would inhibit corrosion, but most terminals aren't subject to corrosion, so......

Remember, there are two types of "electrical grease"... One inhibits conduction, one increases conduction (has copper powder or another conductive substance mixed with the lubricant) so be sure what you're "slathering" inside the plug.

My thoughts, for what they might be worth, if you do want to apply dielectric grease, coat the terminals sparingly to prevent contact with moisture/air, but don't put a "big gob" in there, thinking it would seal the contacts. Once the plug sits in the sun, that grease will soften and start oozing out of any opening in the plug. That will make it a mess to handle, possibly leak in the carpet in your storage bay and would be hard to clean up. So, apply sparingly, if at all.

[xrated]

A couple of suggestions for you. On the female part, trim off the excess wire that is protruding past the end of the wire clamp....no need for it to be that long and it just pos it closer to the other wire in the plug body. #2. On the male plug...the cable clamp......loosen it up and slide the outer jacket of the cable completely under the clamp. Right now the clamp is clamping on the individual wires slightly. That a problem just waiting to happen

[sourdough]

Originally Posted by xrated

A couple of suggestions for you. On the female part, trim off the excess wire that is protruding past the end of the wire clamp....no need for it to be that long and it just pos it closer to the other wire in the plug body. #2. On the male plug...the cable clamp......loosen it up and slide the outer jacket of the cable completely under the clamp. Right now the clamp is clamping on the individual wires slightly. That a problem just waiting to happen

^^^^What he said!! Dielectric grease? VERY sparingly if at all would be right IMO. Might cause more issues than it helps.

The ends of the old cable look very eaten up. With that much damage what do the receptacle ends look like? They may be just as bad and require replacement. Also, are we sure that it is just the connectors that are causing the heat buildup or could there be something else causing it? What gauge is that wire in the cable? 12,14? Is it the only cord you use from the camper to the plug or is it an extension with another cord? Just don't want you to fix the obvious but miss an underlying problem.

[JRTJH]

While we're on the subject of electrical connections, I was always taught that it's OK to use the "push-pin type inserts" on the back of plugs for 14 ga, (15 amp) wiring, but to use the side screw connectors for 12 ga (20 amp) and higher rated wiring. It's "standard practice" to form a "U" of the wire, to maximize contact with the screw/plate in the connector. For reliability, I've always "tinned" multi-strand wire in any plug that I've replaced. Tinning reduces the potential for corrosion to "eat away" at the single strands, making the connection more durable and significantly increasing the ability to maintain high amperage loads in adverse conditions like are found in RV applications. YMMV.

[sourdough]

Ben, did you have any luck with the power cord repair?

I've thought, and worried, about your situation. I asked the question about the gauge of wire for a reason. I have seen and repaired many burned plugs, receptacles etc. My concern for you is this: I have seen burned "plugs" and I've seen burned "outlets". Usually you have two, the plug that plugs into the receptacle and the outlet if heating up badly. What you have shown, to me, is a "30A" extension cord burned up on both ends. Problematic - no thrown breaker.

To me, you either had a very old cord with very deteriorated ends AND receptacles or something else could be going on. To me, those ends of that cord look like you are trying to pull too much current through that extension cord (gauge?). It's frying the ends of the cord but not throwing a breaker because the gauge of the wire can't carry the load...it just burns up the cable/connectors.

You had not posted back and just wanted to throw that out there...should have in the first place but thought we might get a status. Hope all is well.

[xrated]

Originally Posted by JRTJH

While we're on the subject of electrical connections, I was always taught that it's OK to use the "push-pin type inserts" on the back of plugs for 14 ga, (15 amp) wiring, but to use the side screw connectors for 12 ga (20 amp) and higher rated wiring. It's "standard practice" to form a "U" of the wire, to maximize contact with the screw/plate in the connector. For reliability, I've always "tinned" multi-strand wire in any plug that I've replaced. Tinning reduces the potential for corrosion to "eat away" at the single strands, making the connection more durable and significantly increasing the ability to maintain high amperage loads in adverse conditions like are found in RV applications. YMMV.

And also, of equal importance.....make sure the the end of wire loop is ALWAYS pointing in the clockwise direction as you tighten the screw. If you point the end of the wire in the counter-clockwise direction, as you tighten the screw, it will tend to make the loop open up and the wire not fully under the screw head.

[cavediver]

To follow up on what sourdough said breakers need to be sized to the wire . 15 amp 14ga.- 20 amp 12ga -30 amp 10ga. If you use to big of a breaker 50amp and your running 10ga wire your not protecting the wire. You can over draw the wire and not trip the breaker. The breakers are there to do one thing only, that's to protect the wiring. And not turn your RV into a toaster.

Jack

[flybouy]

All good advice on trimming excess wire, tinning the wire ends (that means soldering the bare wire) and the question on wire size. As it's difficult to judge the actual wire size from the photos the cable sheathing (the black outer part) should be impressed with the wire size and number of conductors such as 12/3 for #12 wire with 3 conductors. I have seen some non american made products "cheat" on wire size so if it doesn't carry a UL label be weary.

[alien_scones]

Tha is for everyones replies and concerns.

I redid both plugs with everyones concerns.

I redid the extension cord at home and the rv cable at the KOA in Tucumari NM while watching a mini haboob roll through.

The only melted ends were the ones I pictured. The other Male end of the extension cord and my female household outlet didn't have any scoring or melting.


This isn't the first time the RV plug has melted. It was replaced under the route 66 warrantee but I didn't ask why and they didn't tell me .

I added a sanding block to my landing kit. I'll sand each terminal before I plug it in.

My next question is what if the female plug is all messed up, carbonized and waiting for the next victim? Is there a tool or makeshift tool to sand/clean the female plug?

Btw, before I posted my question I genuinely tried to search for this topic here. Can anyone suggest better search terms to bring up this topic? I'm not the first one to experience this and I'm somewhat ashamed I couldn't find answers using the forum search feature

[alien_scones]

Originally Posted by flybouy

All good advice on trimming excess wire, tinning the wire ends (that means soldering the bare wire).

Both instructions (for the replacement plugs) said not to solder the connections. Again, I am in an area beyond my expertise. I thought about soldering the strands wires into a single, uh, core? Not sure if tinning and soldering are the same thing.

So, assuming what I've read so far, it's to solder the strands together but don't solder the wire to the connector?

[sourdough]

Don't worry about the lack of search results and don't feel bad for asking a question. We don't mind helping. I've had difficulty many times trying to find a post or thread I know I've read but can't get the right word or ??? to get there.

If you are repeatedly burning up the cable something is definitely wrong and the cable is apparently the "weak" link. That's not safe and something catastrophic could happen. If you have replaced the ends on the same cable that destroyed the previous ends I'm afraid you're going to have the issue again.

Do you know the gauge of the wire in that cable? If not, as a previous post noted, it should be imprinted on the cable itself. I'm still not sure of your connections, but, DO NOT stick anything into the female outlet to clean it unless power is disconnected. Your new plug should plug into the receptacle and be tight to very tight. If it just slides in and is any sort of loose replace the receptacle. And, check the size of that wire - I'm afraid it's your problem.

[SteveC7010]

Originally Posted by alien_scones

Both instructions (for the replacement plugs) said not to solder the connections. Again, I am in an area beyond my expertise. I thought about soldering the strands wires into a single, uh, core? Not sure if tinning and soldering are the same thing.

So, assuming what I've read so far, it's to solder the strands together but don't solder the wire to the connector?

You guessed correctly. Common definitions: Tinning is coating an item with solder. So tinning the end of a stranded wire bonds the strands together. You could also tin a solid wire, but that would usually be in preparing to solder the wire to something else. Soldering is joining two or more items together. They could be two wires or one or more wires to a terminal, etc.

A side comment: whenever possible I prefer to crimp and solder when using crimp terminals of any type. I know this means abandoning the plastic insulator, but I'm a huge fan of heat shrink tubing.