The dock hand at the last marina I was at must have shorted my plug. The cord works but would you use this cord?
Scorched Plug
- Thread starter Sailgunner
- Start date
No. See the attached links.
Hall of FAIL – Marine How To
Shore Power – SmartPlug vs. 1938 – Marine How To
Hall of FAIL – Marine How To
Shore Power – SmartPlug vs. 1938 – Marine How To
Ditto Dave's answer. That black stuff is an early warning that something is wrong in the circuit. Was that plug at the dock pedestal or the boat? Ours is at the dock with the cord socket at the boat. I'm still confident of the original style of shore power cord rather than the smart plug. To each his own. I've attached a strain relief on each end of the cord so that any boat movement will be absorbed by this relief. I also cleaned up the shore power circuit on our boat just to stay on top of these matters. Both cords for our boat remain free of any scorching or discoloration. That was not always the case; another story.
The plug is replaceable and not terribly difficult to mount to your existing cord. If however you need weather/waterproofing that's generally an entire new cord replacement. Our dock receptacles are weather proofed by the enclosure.
That's part of the problem. Usually it's just the plug that fails due to a bad connection.
It appears the smart plug is for the boat side of the cord, not the dock side. I ordered a new male plug.
It is. My point was that once you needed a new end anyway, you could turn the cable around, cut the bad end off and put the SmartCord (boat) end on, and swap the inlet.
How is it that the dock hand did this?
I have 2 30 amp twist lock inlets on my boat. They are perfectly fine after 9 years of use at many dozens of marinas while cruising full time. The reason...I NEVER exceed 20 amps per cord. The design should be de-rated to 20 amps. The boat came with several burnt cords which I suspect were loaded well over 20 amps to run AC's for extended periods, I replaced them and have had no issues since.
I have 2 30 amp twist lock inlets on my boat. They are perfectly fine after 9 years of use at many dozens of marinas while cruising full time. The reason...I NEVER exceed 20 amps per cord. The design should be de-rated to 20 amps. The boat came with several burnt cords which I suspect were loaded well over 20 amps to run AC's for extended periods, I replaced them and have had no issues since.
I doubt the dockhand did this, I think he just noticed it.
Where's Maine Sail when you need him? I'm sure he would have several well found theories about how this happened. In the meantime I'd suggest some of the following theories:
1. The plug has been gradually failing for a long time. It was only the last time it was plugged in that the failure became noticeable.
2. The current draw on the cord has been pushing the limits of a 30 amp circuit for a long time and the evidence finally became visible.
3. The pedestal at the last marina the OP visited has some significant wiring issues.
The good news is that the fail happened at the pedestal end, not the boat end. With a failure at the pedestal the dock will burn down, but not the boat.
One way to reduce the risk of burnt cords is to avoid plugging into the pedestal when equipment is turned on in the boat. Especially hot water heater, ac, or space heaters. If high loads are on, there will be arching as the pos. and neutral probes are inserted in the pedestals receptacle. Not a problem at first, but over time the residue from the arcing will build up and cause high resistance, and heat. Not only on your plug but also in the female receptacle.
Corrosion on the contacts probably caused this. That, or the plug was not sufficiently inserted/twisted into place. If it was a high-amp load, I'd expect 2 conductors to be burnt/melted. In either case, the contact heats, that leads to heating the cable's wires attached inside the plug. The insulation around the wires melts, and when it melt back along the cable, they will be bare where they touch each other. SHORT CIRCUIT! FIRE! I just bought that smart plug set at the boat show. 30 amp, 177$.
Bingo!!! Heritage nailed it. I failed to mention it in my post. Thank you heritage for your sage advice.
A practice that I learned many years ago from a marine electrician, after purchasing Belle-Vie, was to shut off the main breaker on the boat BEFORE unplugging/plugging shore power. Our dock pedestal does not have a breaker switch. If current is flowing when you unplug/plug the cord at either end that can cause some arching, and over time result in weakening/burning the spade contact points. Shutting off the flow of electricity needs to be your first step.
Probably caused by a worn out pedestal receptacle. Once the contacts inside the receptacle lose their spring tension grip on the male prongs of the cord cap electrical arcing begins. Take a look at the pedestal receptacles throughout your marina and you will probably see that similar scorch marks on the receptacles are quite common. Marinas typically never replace these until they become totally inoperable.
While this is one part of it, and a best practice that one should always do, it is by no means a preventive measure against the twist-lock receptacles losing spring tension, corroding or over drawing the receptacle and creating high resistance.
Arcing can certainly lead to an earlier high resistance failure, but loose spring tension, high amperage use, and corrosion would be the leading causes I see. I would say that over 80% of the burned up cord ends I see have no signs of arcing burns at all...
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,141
I do not understand this thought. Dock on fire, dock burning down, boat tied to dock. How does the boat escape the fire?
You guys identified the issue. The dock plug under load when being unplugged. Turn off the boat. Before you unplug. Shut down the dock circuit breaker, if you have one, before removing plug. Notify the marina of service need on dock pedestal. Cautionary notice will help you recover boat cost should pedestal fail.
I like the science of the “smart plug”. I switched.
Available right here. https://shop.sailboatowners.com/prod.php?7066
A little tongue in cheek. If the plug starts a fire on the boat, the boat is by definition on fire. If the fire starts in the pedestal, there is a chance that someone will notice and put it out before it gets to the boat or the boat will get moved.
