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Old 31-07-2009, 09:01   #1
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Burnt Power Cords

I keep burning up shore cord ends, and the outlets. They never throw breakers at the shoreside hook up or on the boat. Which leads me to believe that there are arch spots or something in the cord ends that are producing resistance thus heat. But I can't see any problems spots. The next thing would be to spilt the AC load center with two cords. But before cutting new inlet sockets into the boat and buying spitters I thought I would ask the experts!!!!!!!! And if splitting the circuits up would you use a 50 amp to two 30 amp cords, or just split off with a 30 amp to two 30amp cords. The main on the boat is a 30 amp

Denny and Diane
Lagoon 37
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Old 31-07-2009, 10:02   #2
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Burning up shore cord ends, and connectors, is pretty common. Unfortunately. Three causes:

1. Overloading -- trying to pull too much current;
2. Poor maintenance, leading to corroded or loose connections; and
2. Overspecification of 30A connectors.

Overloading can occur because of failure to understand that a 30A circuit cannot be expected to deliver 30A continuously. Rather, they should not be loaded more than 24A or so, even when new and shiny. Now, 24A isn't much, if you count air conditioning, refrigeration, battery chargers, hot water heaters, and all the other heavy loads. Often, as well, boats aren't wired in such way as to keep you out of trouble, either. I lived aboard a houseboat for many years which -- straight from the factory -- was wired in such way that you could try to pull 90A thru the 30A connection!

Poor maintenance. You need to pay attention to your shore cords. Make it a habit of touching them near the power pole and where they attach to the boat whenever you leave or come aboard. You'll be able to spot heating that way. Keep them water tight. Do your best to keep them clean and make sure they are making a good connection at each end.

Overspecification. IMHO, 30 amp cords are way overrated. They can't carry that much current continuously, even when new. Their configuration is such that they very shortly deteriorate. If you add a splitter so that you get two 30A connections, you in one way add some capacity, but you also add a potential danger: the only CPD protecting those two 30A cords is the 50A breaker on the dock, meaning that you could pull 50A thru EACH of those cords before the circuit breaker on the dock would think of tripping. This could get you into real trouble.

If you have the option, you'd be much better off with one 50A shore cord leading to a 50A connector on the boat (same physical size as the 30A one). From this inlet, you could have two honest-to-god 50A 120VAC circuits, i.e., much more than you could get from two 30A cords. To do this, you'd have to upgrade your wiring on the boat from the inlet to the panel(s), using AWG6 wire instead of the AWG10 wire which you most likely now have. And, you'd have to upgrade the main breakers to 50A.

The conversion isn't cheap (connector and shorecord prices are astonishingly high), but it's definitely the way to go if you have the $$$ and the desire to never again worry about having enough onboard power :-)


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Old 31-07-2009, 10:13   #3
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The voltage difference between the dock outlet and the boat will tell you at what point you are starting to draw too much current.

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Old 31-07-2009, 10:39   #4
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At best, that's a rough indicator and very hard to calibrate. For example, a typical 50' AWG 10 shorecord would show a 3.5 volt drop at the end of the cord with a 30A load. On board, the drop actually might be greater due to unusual resistances in the inlet connection, poor wiring, etc.

Bottom line, though, is that the problem isn't due to the size of wire used in 30A shore cords. Rather, it's due to the poor connector design.

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Old 31-07-2009, 11:01   #5
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if you are talking about the plug getting burnt, I have not had a problem since I added strain relief
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Old 31-07-2009, 13:29   #6
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It's a pretty common problem living aboard in winter and running a small elect heater. I've had to change many an end before and the copper looks pretty bad when I change them. I usually would change an end once and then buy a new cord. I would not go to 50 amp... the cords are very expensive and some marinas only have certain (large) slips with 50 amp service. Most people go to two 30 amp services in lieu of 50 amp. A 50 amp, 50 foot Marinco cord retails for $794 and can be found for $470 bargain huh! a 30 amp retails for $125 and can be had for $74... sometime you can get them for $39... get the picture? Never mind if your Paul Allen or Bill Gates... option 1 will fit your boat just fine....

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