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Old 11-22-2017, 08:13 PM   #1
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Internally Shorted 30Amp Power Pedestal Plug

Back in late Sep we were camped at the US Naval Academy FAMCAMP. The sites are all wooded, gravel, and fairly level. There is electric & water, but no sewer hookup.

On about the 4th day of camping I decided to disconnect power & water and go to the dump site to dump my black & gray holding tanks. I turned off water at the pedestal and turned off the circuit breaker at the power pedestal. When I turned to go to the RV and disconnect power and water, I noticed the power cable connector plugged in the side of the RV was angled down at about a 60 degree angle.

I thought that was more than a bit odd, and after I spun the power cord locking ring, the power plug connector would not disconnect from the connector on the outside of the RV. I eventually pulled hard enough to get the plug out; however, the hot terminal pin on the RV connector had fused to the hot pin on the power plug. Pulling the plug resulted in me pulling the hot pin out of the connector on the side of the RV.

Long story short -- the connector on the power pedestal had shorted internally and a surge burned my 20' power cable the length of the hot wire in the cable and caused the hot pin in the RV connector to fuse to the hot pin in the cable connector. I had to get an RV mobile repair to bring me a new cable and replace the connector on the outside of my RV. The FAMCAMP host had Navy maintenance replace the connector on the power pedestal. I have filed a claim with the Navy Tort office.

And here is something hard to believe -- I had my surge protector plugged into the shore power plug and it never detected the surge or popped off.
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Old 11-22-2017, 08:28 PM   #2
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Wow!
I guess you're lucky that the damage was pretty limited.
Is there any way to test your surge protector? If it malfunctioned: I wonder if there's any responsibility for your damages, that the manufacturer will pay for?
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Old 11-22-2017, 08:39 PM   #3
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Bob -- I have a claim in against the Navy since it was their power plug that caused the problem.

I agree with you -- the surge protector should have -- well done what its name-sake says -- protect against a surge. It is the $90 Progressive Industries portal protector. Think I need to invest in a better one.
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Old 11-22-2017, 08:41 PM   #4
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Wow! I wouldn't have thought that possible. That takes a big load to get arcing enough to burn that way. And there's no damage to any of the internal circuitry or electronics? You're lucky to have caught it when you did!
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Old 11-22-2017, 09:22 PM   #5
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Usually electric connections get hot when there isn't a very good connection: All the current is forced through the small connection point heating it up.

I had a coworker with a bad charge cable on their EV with a similar problem. In his case the pins didn't fuse but the heat did melt the plastic of the plug on the car:
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(The problem there was that the cable connector used wasn't rated for the 30A his car charged at. He still had to get the plug in the car replaced--twice! before he solved the problem)

Did they check the plug at the pedestal when they changed it?

I ask because usually the melting happens at the point of the problem, not 20' "downwind" of it (and I wouldn't put it past Thor to have something wrong there at the camper connector).

I also would suspect your surge suppressor didn't trip because this was probably a longer term event than it is setup to handle (surge suppressors are designed for that lightning hit, not a minutes long event).

Ah I can see that if the neutral line in the pedestal shorted to ground something like this could happen as your pin at the RV might have been the weakest link, however.
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Old 11-22-2017, 11:11 PM   #6
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Originally Posted by JamieGeek View Post

.....cut.....

Did they check the plug at the pedestal when they changed it?

I ask because usually the melting happens at the point of the problem, not 20' "downwind" of it (and I wouldn't put it past Thor to have something wrong there at the camper connector).

I also would suspect your surge suppressor didn't trip because this was probably a longer term event than it is setup to handle (surge suppressors are designed for that lightning hit, not a minutes long event).

Ah I can see that if the neutral line in the pedestal shorted to ground something like this could happen as your pin at the RV might have been the weakest link, however.
I'm not following the scenario you are describing. How would a short between neutral and ground at pedestal cause the motorhome's plug to overheat?

I agree with your first statement that a short at pedestal would cause overheating there for the most part, but I'm wondering why it wouldn't trip the breaker. I must be missing something here.

A good plug should not overheat unless more than 30 Amps flows through it. I'm not seeing how that would happen right off the bat. Why wouldn't RV or pedestal breaker trip first?
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Old 11-22-2017, 11:35 PM   #7
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Chance -- the maintenance folks from the Navy Public Words verified that the plug on the pedestal was bad (all kinds of arcing and melting around the hot pin). They replaced the plug on the pedestal.

Jamie -- electrician from Navy Public Works said basically what you are saying. It was a long term event. There was significant arcing and melting evident in the box where the plug was mounted on the pedestal.

When I noticed the power plug drooping down after I had opened the CB on the pedestal, there had still been power on the RV. The A/C was running, converter was operating -- basicaslly there was no indication that there was a problem anywhere.

Here's another picture of the connection on the RV. You can see the melted plastic debris in the bottom of the connector. You can also see the size of the hole at the top where the hot pin that fused to the connector was. If you go back to the first pix I posted you can see that there was heat damage to the male plug end of the 20' cable on the connector that was plugged into the surge protector. So the overload affected the plug in the pedestal, the plug on the 20' cable that was plugged into the surge protector, and also the opposite end of the 20' connector, and the connector on the outside of the RV.

Aside from damaging the connector on the outside of the RV, there was no other electrical damage done to the RV -- wiring, transfer relay, converter, etc. I suspect that had I not shut off power when I did, the 20' cable connector would have continued to droop down as the fused hot pin would eventually become disconnected from the RV wiring. At that point there might have been a larger short on the back of the RV connector, and that surge might have caused a whole lot more damage.

Glad I caught it when I did. The cost was $170 for a new RV connector and 20' cable, $117 for the mobile RV dispatch and labor.
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Old 11-22-2017, 11:35 PM   #8
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As Jamie pointed out corrosion could certainly cause a connection to get very hot, without tripping the breaker. Essentially you have a load, say 25 amps on a 30 amp circuit, which would not trip the breaker, but if corrosion causes it to only be able to flow though a very small contact point, you now have a situation of drawing too much current through too small a contact point. Electrical fires start from this very condition all the time, but do not trip breakers in time, because the current draw does not exceed the breaker capacity.
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Old 11-22-2017, 11:36 PM   #9
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Ed all I can say is WOW!!! Glad you were there and the damage was limited!
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Old 11-22-2017, 11:36 PM   #10
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Forgot to attach other pix.

And Laco's description I think is exactly what was going on where the two connector pins were fused. The contact point between the two pins had become very small.
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Old 11-22-2017, 11:55 PM   #11
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When you were hooking your power cable up to the box; did you happen to notice anything that looked... unusual?
I guess that a better question to ask might be if there's anything specific that someone should be looking for, when hooking up the electric?
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Old 11-23-2017, 12:51 AM   #12
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Quote:
Originally Posted by Chance
I'm not following the scenario you are describing. How would a short between neutral and ground at pedestal cause the motorhome's plug to overheat?
I was merely speculating that the short to ground would provide an additional current path from the pedestal through the RV and back out into ground (possibly lower resistance causing more current to flow). Of course that probably wasn't the case especially since he was running the A/C so it could merely have been a few bad connections causing all the current to run through them heating them up.
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Old 11-23-2017, 12:58 AM   #13
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Chance -- the maintenance folks from the Navy Public Words verified that the plug on the pedestal was bad (all kinds of arcing and melting around the hot pin). They replaced the plug on the pedestal.

....cut....
No doubt, but in what order did the failures occur?

A pedestal failure shouldn't affect your RV the way it did as far as I know, but a failure at the RV connection that shorts can then overload the cord and pedestal, causing damage there before breaker may trip; particularly if breaker at pedestal was bad. Often accidents/failures happen when multiple things happen concurrently.
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Old 11-23-2017, 01:04 AM   #14
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Tonight on engineering disasters...
LOL sorry..watch those shows now and then and it always is many things all happening in concert that causes the failure.

Chance is thinking along with what I was thinking: Over time it is possible that your RV connection got corroded or deteriorated in some way that reduced that one pins contact causing the same amount of current to go through a smaller and smaller connection point until it started warming up enough to melt everything causing what you had.

At the point that it melted it could have caused the problems in the pedestal (and not the other way around).

Either way the scary thing here is that none of us think twice about plugging in. You simply plug in and walk away--does anyone inspect the pins other than a cursory glance? It also is possible that the problem wasn't the pin but the socket--something that isn't easily inspect able.
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Old 11-23-2017, 02:52 AM   #15
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Originally Posted by bevedfelker View Post
....
I agree with you -- the surge protector should have -- well done what its name-sake says -- protect against a surge. It is the $90 Progressive Industries portal protector. Think I need to invest in a better one.
Well... not sure any surge suppressor would catch that...
I expect you didn't have a VOLTAGE surge... Or even an over/under voltage event - either of which your surge suppressor would have caught.

If amps had been exceeded at the pedestal, the pedestal breaker would have tripped... Assuming it was functional.... A bad breaker could have allowed too much current - still not an event a surge protector would trigger on.

As Laco said, sounds like the connector developed high resistance... Too much current then flowing thru small contact area generating excessive heat.

Which failed first? Could be either...
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Old 11-23-2017, 11:24 AM   #16
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So does anyone know how to clean your contacts the best way? I had a surge suppressor melt this way and I took some light sandpaper to the leg that was scored. Any other thoughts?
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Old 11-23-2017, 12:35 PM   #17
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Originally Posted by JamieGeek View Post

.....cut.....

Either way the scary thing here is that none of us think twice about plugging in. You simply plug in and walk away--does anyone inspect the pins other than a cursory glance? It also is possible that the problem wasn't the pin but the socket--something that isn't easily inspect able.
I do occassionally now, but only because I had a similar failure with an older rental motorhome that had gotten a lot of use (nearly 100,000 miles).

In that unit the power cable was hard wired at motorhome, and during travel the 30-Amp plug was to be connected to generator. At one campground when I unplugged from generator so I could connect to pedestal, one pin remained in generator plug.

I shouldn't have, but rigged it anyway to finish trip and get back home. Since then I sometimes check pins on male plug to make sure they are firm to touch (don't pull hard though which could damage it).
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Old 11-23-2017, 01:07 PM   #18
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I do occassionally now, but only because I had a similar failure with an older rental motorhome that had gotten a lot of use (nearly 100,000 miles).

In that unit the power cable was hard wired at motorhome, and during travel the 30-Amp plug was to be connected to generator. At one campground when I unplugged from generator so I could connect to pedestal, one pin remained in generator plug.

I shouldn't have, but rigged it anyway to finish trip and get back home. Since then I sometimes check pins on male plug to make sure they are firm to touch (don't pull hard though which could damage it).
Right but your use case is a little different: Since you're renting there you kind of are looking around because it isn't your camper so you are doing extra checks.

If it was your camper you may give it a once over at the beginning of the season and then not think twice about anything. Why would you/us? It worked before and no one else has touched it.
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Old 11-23-2017, 01:12 PM   #19
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So does anyone know how to clean your contacts the best way? I had a surge suppressor melt this way and I took some light sandpaper to the leg that was scored. Any other thoughts?
Spray the pins with contact cleaner and use a small stainless steel or brass wire brush and scrub throughly once or twice a year.
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Old 11-23-2017, 02:39 PM   #20
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Well... not sure any surge suppressor would catch that...
I expect you didn't have a VOLTAGE surge... Or even an over/under voltage event - either of which your surge suppressor would have caught.

If amps had been exceeded at the pedestal, the pedestal breaker would have tripped... Assuming it was functional.... A bad breaker could have allowed too much current - still not an event a surge protector would trigger on.

As Laco said, sounds like the connector developed high resistance... Too much current then flowing thru small contact area generating excessive heat.

Which failed first? Could be either...
I agree with GMC. When I was a young man I was a member of a volunteer fire department. We had a house fire started by a lose connection in the dedicated reciptical for a window air conditioner. It turned out that the hot leg became lose and arced to the connection for the load ie. air conditioner. The fuse didnít blow because the amperage draw was controlled by the amps being drawn by the air conditioner. If the hot leg had made contact with either the ground or neutral the amperage would have spiked and popped the breaker. But as long as the path to ground is limiting the amperage, a breaker or I suspect a surge protector will not engage to cut the power and heat will continue to be generated at the connection.

As long as we continue to rattle over rough roads I guess I need to add checking electrical connection to my propane connection check list. And I thought I would have nothing to do when I retired.
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