Shore Power - Hidden Danger

[Just Dreamin']

A real time hazard to be aware of!
This past Friday I converted my shore power system from the current twist and lock receptacle to a SmartPlug System. Extremely easy, took about 45 minutes including time for a t-storm to pass through the marina. The kit included all necessary items to make the conversion as effortless as possible with the hardest part being threading the old shore power cable into the new connector. Not sure why I finally decided to make the conversion other than after research I liked the theory and safety aspects. As my good friend , Jeff Marcum, on The Get~Aweigh, told me I just wanted something to do on the tug. 😀
Now for the heart of this post. After shutting down power by tripping breaker at shore box and unplugging the power cord I went to remove the boat side inlet receptacle - so far so good came out very easy. Started to remove the hot-neutral-ground wires and found I could not remove either the black hot wire or the white neutral. Clipped them off and proceeded to install the SmartPlug Inlet Receptacle. Finished project, connected shore power and all worked great. Happy.
Took the old inlet receptacle and started surgery. It was certainly an eye opener and something which really scared me - a catastrophic failure in the making? Not only was the neutral wire glazed in place from heat but the hot wire was down to less than 75% wire remaining. See photos. To see larger view click on photo.

The whole shore power system is one which at least in my case was - it works no worries. I would inspect all visual contacts and blades each time I disconnected and all was good and shiny not showing any indication of over heating. However, what was going on internal to the receptacle is something we do not see or, again, in my case one area I never looked at.
This may become a winter check item as to remove the boat receptacle, inspect and replace is about a 10 minute job. No sealer to contend with, 4 screws and a rubber weather gasket.

 

[South lake]

And now I have a project added to my list. Wow. Those photos tell the story. Thanks for sharing Mike. I remember Baz posting about making a similar upgrade and this shows why it makes sense.

 

[baz]

Mike: My question is of course.... what on earth caused that scary eye opener ?

1) Was maximum current being drawn at some time in the past ?
2) What appliances have you been using on the boat when on shore power ?
3) How long has the stock boat-side shore power been installed for ?
4) What brand/make/length of shore power cord have you been using ?
5) What is the state/condition of the dock-side shore power receptacle like ? You've seen one end and surely the other end needs to be examined now.
6) Have you been coiling the shore power line onto itself or stretched out in a line ?
7) Have you used more than the standard 50' cord ? ...such that you've connected two 50' cords ?
8) Suggest you also check the SmartPlug connector on the boat and on the boat-end shore power line as well.
9) Maybe the original shore power cord is in some way defective; maybe then replace with a complete new Cordset supplied by SmartPlug.
10) Has the connection to the boat's shore power receptacle been under any stress in the past ? ; such as being pulled at an angle, stretched out due to boat's movement at the dock, screw cap not firmly tightened or being tripped over.

I will be converting my shore power corset to be a Smart Plug product soon after our new R-27 is delivered.

 

[captstu]

The problem Mike and Judy discovered is very common. I think it is caused by the fact the twist lock plug is used in Marine contact don't make 100% contact and less the twisted clockwise very tightly.

The smart lock plug has a double safe mechanism that make sure it's all the way in and locked in the place. Wherever it is on your priority list to change out your twist lock for smart lock, move it up higher.

 

[baz]

The problem Mike and Judy discovered is very common. I think it is caused by the fact the twist lock plug is used in Marine contact don't make 100% contact and less the twisted clockwise very tightly.

From the two photos it appears that the wiring failed in some way and not the pins being in loose contact due to screw cap not being secured enough.... but it really is unclear why it failed so badly with heat and loss of wires.

The smart lock plug has a double safe mechanism that make sure it's all the way in and locked in the place. Wherever it is on your priority list to change out your twist lock for smart lock, move it up higher.

I thought one of the Smart Plug products provided some form of temperature alert at the connection, but don't see that listed anywhere now.

 

[captstu]

I've seen a few of these failures. - I'm guessing about the pins being the cause since the rubber at the pin base melted. But, your post makes me think it was the wire connection that heated first. Just a guess.



Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[NorthernFocus]

...From the two photos it appears that the wiring failed in some way and not the pins being in loose contact due to screw cap not being secured enough.... but it really is unclear why it failed so badly with heat and loss of wires...

Heat related failures often cause so much damage, discoloration, etc, that the root cause is often hard to determine. But heat around electrical contacts is nearly always due to high resistance or arcing. So either corrosion or the terminals were never properly tightened during original installation. Or both.

I have the same vintage R25 and have had to correct a lot of electrical issues at least some(and I suspect all) of which were clearly from original assembly. It seems Ranger was experiencing growing pains back then. At least judging by many changes they made on the R27 it seems they learned a lot with the early 25s.

 

[knotflying]

Several issues can cause the problem. A poor connection at the screws is definitely a problem. And I am talking about the maile connector mounted on the boat. They should be clean, tight and protected with dielectric grease or corrosion block. Clean contacts, even on the Smart Plug are important. Also, clean contacts at your pedestal connection is very important. Fires often happen at the pedestal.

 

[Jake]

Several issues can cause the problem. A poor connection at the screws is definitely a problem. And I am talking about the maile connector mounted on the boat. They should be clean, tight and protected with dielectric grease or corrosion block. Clean contacts, even on the Smart Plug are important. Also, clean contacts at your pedestal connection is very important. Fires often happen at the pedestal.

Can the corrosion block be applied to all the surfaces including all the electrical contact points?

 

[Fowlnest1]

Had similar problem with burn marks on shore power cord.Mentioned to dealer and was in formed the reason was I had not twisted cord enough to lock.Bought new power cord.Same thing.Dealer removed receptacle and found factory had not secured wiring.

 

[knotflying]

Corrosion Block can be put on anything prior to corrosion forming. It will not remove corrosion. It is especially good on wires, as it works its way up the inside of the insulation. On the contacts for the shore power at the boat connection I would be more inclined yo use dielectric grease sparingly. The problem I have with grease is that it can collect dust and dirt. I keep my smart plug connected at the boat all the time, so there is a small chance of collecting dirt and dust. I created a small rack under the gunnel to wrap my cord on and it is out of the way, connected and ready to go to shore power.