Overheating shore power cable, surge protector

[bpaikman]

1. First noticed an indicator light on the surge protector that warned overheating. Everything else was green (50 amp)
2. Inspected and found indications of overheating (slight warping)
at the shore power plug,
and each end of the 120 foot 50-amp extension cable,
and the surge protector
.... no indication of overheating at the house outlet. where we plug in when loading RV.
3. electrician came out and inspected it found a loose prong on the shore power plug from the RV. that prong corresponded with every plug that showed heat damage. He believes that is the cause of all the trouble. However he did tell us it was a very hot day.. that's a black cable lying out there in the sun. He thought it might still work. indeed, it was working fine at the time. No alarms in the coach ....we were running 2 ACs on a 95° day with 100,000% humidity.
an electrician for the same company is coming out tomorrow to replace the plug with the loose prong. They think everything else will be all right. In other words tomorrow when we are loading for our 3-month trip we could start running the refrigerator and air conditioners, using the same heat damaged extension cord. (we have already replaced the damaged surge protector).
4. What do you think? Do you think that prong caused all that melting? The damaged places are warped, with no black.
after he replaces the shore power connection plug, we should be good to go for a trip. What we are wondering is could we still use the extension cord and New surge protector.
We cannot replace the connections on each end of the extension cord at this time ..because some parts have to be ordered and we are due to leave Tuesday.
In an abundance of caution, we're considering running the generator to finish loading. But we're worried about the neighbors.
this guy is a professional electrician that works for large company in town, but he only did a visual inspection and to him it looks fine. we're just very leery of a possible electric fire.

 

[TheLooks]

I agree with your electrician, but I would either feel the connections or use a laser temp device for awhile to make sure and set a baseline. Maybe write the temps down for reference.

 

[bpaikman]

I agree with your electrician, but I would either feel the connections or use a laser temp device for awhile to make sure and set a baseline. Maybe write the temps down for reference.

that's a good idea.

 

[GTS225]

120 feet of "50 amp" cord is an awfully long run. Do you know what gauge the wire is? Gauge and length determine what the cord is capable of withstanding.
Cord connectors will overheat things as you describe. The screw terminal inside the connector gets a little loose over time, there's a bit of voltage drop, but the current demand stays the same. Things get a little warm, the connection loosens a bit more, and it ends up being a vicious circle, until you experience what has happened.
A new connector, (both male and female), will most likely fix things. You might loose a couple inches off that cord.
You might try to relieve your current draw by running just one A/C unit until you can get both cord ends swapped out.
Be safe.....you don't want a fire at 2am in a campground 1300 miles from home.

Roger

 

[Rich W.]

50 amp RV cables are typically 6awg and for a 120’ run at 50 amps at 120v allowing for a 3% drop you should be running 4awg. That may be the cause - see what your electrician thinks about that.

 

[bpaikman]

50 amp RV cables are typically 6awg and for a 120’ run at 50 amps at 120v allowing for a 3% drop you should be running 4awg. That may be the cause - see what your electrician thinks about that.

We had the cord built by this company - it wasn't cheap. And it has worked fine until this week.

 

[bpaikman]

120 feet of "50 amp" cord is an awfully long run. Do you know what gauge the wire is? Gauge and length determine what the cord is capable of withstanding.
Cord connectors will overheat things as you describe. The screw terminal inside the connector gets a little loose over time, there's a bit of voltage drop, but the current demand stays the same. Things get a little warm, the connection loosens a bit more, and it ends up being a vicious circle, until you experience what has happened.
A new connector, (both male and female), will most likely fix things. You might loose a couple inches off that cord.
You might try to relieve your current draw by running just one A/C unit until you can get both cord ends swapped out.
Be safe.....you don't want a fire at 2am in a campground 1300 miles from home.

Roger

6 gauge

 

[bpaikman]

We had the cord built by this company - it wasn't cheap. And it has worked fine until this week.

50 amp RV cables are typically 6awg and for a 120’ run at 50 amps at 120v allowing for a 3% drop you should be running 4awg. That may be the cause - see what your electrician thinks about that.

yes my husband has discussed all this with company that built cord and they selected that gauge.

 

[Wemustrv]

I do not think I would run with that cord at all. That loose prong is a recipe for disaster. Not only is heat an issue that means there is a variation in power supplied and could effect the many items inside. You are literally playing an electrical fire. You may want to shed all the loads off that leg to reduce demand and heating effect.

 

[GTS225]

OK, the mfgr choose that gauge for the cord, but........... Have you ever reached down and unplugged your vacuum cleaner right after turning it off? Notice how the plug AND cord feels a bit warm? That's because manufacturers engineer things right to the safety margin. Can 6 gauge carry 50 amps?.....yes, but it's right at the margin. They save money over the manufacturing run that way, and the problems-in-the-making are yours to deal with and correct, if you're so inclined.
If that 6 gauge cord were only 100 feet, I'd feel better about it, but 150' is pushing things. That being said, I suspect the mfgr. calculated in (or out) a certain percentage on the assumption you would hardly ever be pulling 50 amps through the cord for 3 hours. (Nat'l Electrical code says anything over 3 hours is not "temporary".) To my brain, that's fudging things a bit, but I'm kinda opinionated.

Oh, and for the record, that 150 foot cord has to be considered 300', as the current has to travel out, and back, in order for it to do the work of operating your electrical system. That's where Rich W's voltage drop figures come in.

And Wemustrv is right to be cautious, but maybe a touch over-reactive. I think I would have ALL FOUR cord ends inspected at the very least. (Meaning the cord ends and receptacles, male and female.) That way, potential problems can be corrected or replaced right then, not when it starts showing heat damage the next time. (Tighten all the terminal screws, look for signs of heating, etc.)

Just me talking.....Roger

 

[Rich W.]

I agree with GTS - they probably didn’t base the wire gauge on using a full 50amps all the time for hours on end and you may not be - it would be good to measure the actual load. You can calculate wire size different ways with different parameters, but for 6awg at 50amps 120v continuous load I came up with 84’ max one way distance. Maybe they used 240v in their calcs.

 

[bpaikman]

OK, the mfgr choose that gauge for the cord, but........... Have you ever reached down and unplugged your vacuum cleaner right after turning it off? Notice how the plug AND cord feels a bit warm? That's because manufacturers engineer things right to the safety margin. Can 6 gauge carry 50 amps?.....yes, but it's right at the margin. They save money over the manufacturing run that way, and the problems-in-the-making are yours to deal with and correct, if you're so inclined.
If that 6 gauge cord were only 100 feet, I'd feel better about it, but 150' is pushing things. That being said, I suspect the mfgr. calculated in (or out) a certain percentage on the assumption you would hardly ever be pulling 50 amps through the cord for 3 hours. (Nat'l Electrical code says anything over 3 hours is not "temporary".) To my brain, that's fudging things a bit, but I'm kinda opinionated.

Oh, and for the record, that 150 foot cord has to be considered 300', as the current has to travel out, and back, in order for it to do the work of operating your electrical system. That's where Rich W's voltage drop figures come in.

And Wemustrv is right to be cautious, but maybe a touch over-reactive. I think I would have ALL FOUR cord ends inspected at the very least. (Meaning the cord ends and receptacles, male and female.) That way, potential problems can be corrected or replaced right then, not when it starts showing heat damage the next time. (Tighten all the terminal screws, look for signs of heating, etc.)

Just me talking.....Roger

we agree. We are replacing as we speak. Will keep it in mind about the using that cord for long periods of time. Fortunately? We live in a neighborhood where we would prefer not to annoy the neighbors so we don't keep the motorhome out in the front where we have to load it for very long. We take it back to the storage when we're not loading.

 

[bpaikman]

I do not think I would run with that cord at all. That loose prong is a recipe for disaster. Not only is heat an issue that means there is a variation in power supplied and could effect the many items inside. You are literally playing an electrical fire. You may want to shed all the loads off that leg to reduce demand and heating effect.

we replaced it

 

[bpaikman]

OK, the mfgr choose that gauge for the cord, but........... Have you ever reached down and unplugged your vacuum cleaner right after turning it off? Notice how the plug AND cord feels a bit warm? That's because manufacturers engineer things right to the safety margin. Can 6 gauge carry 50 amps?.....yes, but it's right at the margin. They save money over the manufacturing run that way, and the problems-in-the-making are yours to deal with and correct, if you're so inclined.
If that 6 gauge cord were only 100 feet, I'd feel better about it, but 150' is pushing things. That being said, I suspect the mfgr. calculated in (or out) a certain percentage on the assumption you would hardly ever be pulling 50 amps through the cord for 3 hours. (Nat'l Electrical code says anything over 3 hours is not "temporary".) To my brain, that's fudging things a bit, but I'm kinda opinionated.

Oh, and for the record, that 150 foot cord has to be considered 300', as the current has to travel out, and back, in order for it to do the work of operating your electrical system. That's where Rich W's voltage drop figures come in.

And Wemustrv is right to be cautious, but maybe a touch over-reactive. I think I would have ALL FOUR cord ends inspected at the very least. (Meaning the cord ends and receptacles, male and female.) That way, potential problems can be corrected or replaced right then, not when it starts showing heat damage the next time. (Tighten all the terminal screws, look for signs of heating, etc.)

Just me talking.....Roger

Yup, we did exactly that today

 

[Kevin D Pem]

For those that actually know what they are talking about!!
The electrician talked about temperature for a reason. Generalization can get an electrician in trouble, the reason for my first sentence!

When you suggest replacing wire maybe you should look at prices. Below is a chart, if you can understand it! Please remember these wire size charts are for 86 degree temperature, not the over 100 recorded by the poster.

Just because the wire is sized right at 86 degrees, it is not a one size fits all. At temperatures in the hundreds your cable is undersized so you should plan to either calculate max power for the temperature, and use less power, or increase cable size...(not a popular option).

It may be interesting for sake of argument to check the prices and weight of the cable, before suggesting the latter.

My recommendation is reduce the power demand in high temperatures!

SO Cable Selection Guide

temcoindustrial.com

 

[Rich W.]

My recommendation is reduce the power demand in high temperatures!

SO Cable Selection Guide

temcoindustrial.com

or cable length.

 

[Kevin D Pem]

or cable length.

Yes thhn, conduit, and pedestal! Is the right way to do this job.

 

[Rich W.]

It may not work for the OP’s situation, but I installed this:

 

[Wemustrv]

OK, the mfgr choose that gauge for the cord, but........... Have you ever reached down and unplugged your vacuum cleaner right after turning it off? Notice how the plug AND cord feels a bit warm? That's because manufacturers engineer things right to the safety margin. Can 6 gauge carry 50 amps?.....yes, but it's right at the margin. They save money over the manufacturing run that way, and the problems-in-the-making are yours to deal with and correct, if you're so inclined.
If that 6 gauge cord were only 100 feet, I'd feel better about it, but 150' is pushing things. That being said, I suspect the mfgr. calculated in (or out) a certain percentage on the assumption you would hardly ever be pulling 50 amps through the cord for 3 hours. (Nat'l Electrical code says anything over 3 hours is not "temporary".) To my brain, that's fudging things a bit, but I'm kinda opinionated.

Oh, and for the record, that 150 foot cord has to be considered 300', as the current has to travel out, and back, in order for it to do the work of operating your electrical system. That's where Rich W's voltage drop figures come in.

And Wemustrv is right to be cautious, but maybe a touch over-reactive. I think I would have ALL FOUR cord ends inspected at the very least. (Meaning the cord ends and receptacles, male and female.) That way, potential problems can be corrected or replaced right then, not when it starts showing heat damage the next time. (Tighten all the terminal screws, look for signs of heating, etc.)

Just me talking.....Roger

I have 47 years of experience with circuit breakers and electrical systems as well as sitting on NEC/ NFPA and UL code panels. This is not really overreactive. This is serious problem. See photos to see what bad connections and the heat caused by it can do. These are from my coach which due to a short to ground came close to burning my RV to the ground. The second photo it appears the cable is close to the turbo pipe it is just the angle. While this was not caused by a faulty plug it does show the heating effect.

 

[bpaikman]

For those that actually know what they are talking about!!
The electrician talked about temperature for a reason. Generalization can get an electrician in trouble, the reason for my first sentence!

When you suggest replacing wire maybe you should look at prices. Below is a chart, if you can understand it! Please remember these wire size charts are for 86 degree temperature, not the over 100 recorded by the poster.

Just because the wire is sized right at 86 degrees, it is not a one size fits all. At temperatures in the hundreds your cable is undersized so you should plan to either calculate max power for the temperature, and use less power, or increase cable size...(not a popular option).

It may be interesting for sake of argument to check the prices and weight of the cable, before suggesting the latter.

My recommendation is reduce the power demand in high temperatures!

SO Cable Selection Guide

temcoindustrial.com

we decided to reduce power and covered the cable that was not in the shade with whatever we could find it lying around to shade it