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Shore Power safety
Ok, this shore power plug is on my boat, but it is the same thing on the coach. My Marathon conversion has 2 of these M
arinco 125/250V 50 A receptacles. We have all heard about the problems they sometimes have.
On the boat, when I bought it, there was a small brown spot near one leg of the receptacle. I ignored it because it was working and did not look too bad. But upon closer inspection, it was very marginal, just look at the pic showing the internals.
All has been replaced now! I suggest everyone examine these every once in a while.
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11 Replies
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Good heads up Peter, I have a small brown spot on one of my cords and I’ll check it out. I have a smaller 15′ 50 amp that I use when able instead of the long one and the twist connection on the new cord is much tighter than the old one, so I assume the connection get worn over time.
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There are two things critical for good electrical connections and insuring the connections are safe.
The first is there must be tight terminal connections. Something such as a loose screw causes the connection to get hot and it usually creates the second condition which is resistance. Once a connection gets resistance across it from arcing or corrosion (such as dirty blades on a plug) heat ensues and as the heat builds the results can be like the photos.
Probably long before any physical damage appears there will be a little heat due to the resistance of a loose terminal or corrosion and you can feel the warmth. Not a bad way to sense the early stage of a bigger problem.
But don’t limit the thinking to shore power cords. That condition can be anywhere, including behind the switch panel so for the ultimate in safety it is a neat project on a rainy day to look for signs of loose or corroded connections.
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I carry an infrared heat gun for checking my tires and hubs at every rest stop. The same gun works great to periodically check electrical connections all over the bus. You will find any problems long before they start to discolor.
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Peter,
The problem with shore power cords on boats is all too common. I have had the same happen on two boats in the past. In most cases, the failure is due to the power cable becoming loose over time. The other failure point is that the plug and connector don’t make enough contact to support the current draw. The corrosive environment doesn’t helped. In the marine environment there is better mousetrap. Check out this connector and plug: http://www.smartplug.com/marine.html .
It is never good to add unnecessary plugs. I don’t understand why any converter in the last 10 years or so would configure a coach that would require the use of an extension cord. The use of extension cords adds 4 additional failure points PER WIRE. Marinco retracable power reels have been around for a long time. Today there are others available, as well. If my coach used an extension cord, I’d look for a way to install a power reel.
To someone else’s point, electrical connections should checked periodically for good connections. BTW, the marine industry does not allow single or solid wire electrical wiring. Their rationale is that solid wire will break under vibration well before multistranded wire of equivalent gauge. If makes be wonder why coaches haven’t followed the same rationale.
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My coach does not have soid wiring.
JIM
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Certainly the shore power cord on the coaches is not solid conductor. On my coach, and I assumed all others, the AC inside the coach is solid conductor. This is the wiring from the circuit breaker panel to all appliances or outlets. With solid conductor wiring it’s important that the connects be checked periodically and more importantly that the wiring has plenty of fastners to keep it in place, especially at the outley, appliance, or other termination point.
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The wiring for AC circuits in all coaches is NOT solid copper. That is absolutely inappropriate for the application for the very reasons you state about the need to regularly retighten the connections.
Coaches should have tinned, stranded copper wiring for 120/240 circuits.
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The wiring for AC circuits in all coaches is NOT
solid copper. That is absolutely inappropriate for the application for
the very reasons you state about the need to regularly retighten the
connections.Coaches should have tinned, stranded copper wiring for 120/240 circuits.
I believe thats what ANSI/RVIA specifys ..
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Mine went out this past summer, the replacement cost for the power chord was $4400.
Just to purchase a new recepticle (female end) and not the power chord complete, was close to $1300.
BCO
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Hmmm…you have me questioning what I thought to be true. So, I took the cover off the main AC panel and yes the wiring is solid conductor. I have seen the AC wiring going to/from the inverters on other converters and see that it too is solid conductor. For those that have stranded AC wiring, are you sure?
BTW, the stranded wire doesn’t need to be tinned, although that would be great. Tinned wiring is typically only required in harse marine environments. I guess if you park your coach on on the beach you might want tinned wire.
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Gil,
Trust me. I know exactly what I have had on three coaches.
Solid conductor wiring may be good for some applications, but as a former manufacturer of the power outlets we plug our RVs into I can tell you that the solid wiring used requires retorquing periodically and those devices are stationary. I cannot imagine why solid copper wiring would be used in a motorhome conversion application especially considering that when moving everything is trying to shake itself apart.
My 120 volt wiring uses crimped on terminals and not wire nuts so the connections are secure.
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