Melting Marinco plug on my Honda EB3000 generator. - SailNet Community
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post #1 of 3 Old 08-18-2012 Thread Starter
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Melting Marinco plug on my Honda EB3000 generator.

I ran my Honda EB3000 generator this morning to charge my bank of batteries on my boat. Over the last day or so, I have had a problem where my Freedom 20 suddenly shuts off but restarts in a few seconds. When this happened, I went outside and checked the connection of the cord on the generator. All appeared to be fine and the problem stopped.
Today, I ran the generator again with no problems. When I was preparing to put it away, I pulled out the Marinco plug and found one of the contacts had started to melt on the plug on the cord.
A few years ago when I first bought our boat, I had a similar problem where the plug plugged into the boat. I replaced both fittings(cord and receptacle) and the problem was solved.
Any suggestions on what to do. Is the plug on the Honda side defective and if so, how can I check to see if it is? I have a spare cord(tough to get out here in Fiji) but am a bit hesitant to use it for fear of melting it too(last one I have) if the plug is indeed bad. It ran just fine today but tomorrow is another matter.
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post #2 of 3 Old 08-18-2012
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Re: Melting Marinco plug on my Honda EB3000 generator.

Well, that means that the electricity run through the plug generated heat faster than the plug could radiate the heat away. That happens for one of two reasons. Either there was more current than the plug could handle or there was high resistance where the plug's contact meet the receptacle.

Overcurrent situations happen when the load (i.e. your electrical system) is running too much stuff or has a short or a similar kind of fault. If this is what happened, then you also have a problem with the generator -- the circuit breaker should have tripped.

High resistance situations almost always come from one of two things. The plug was not properly seated and therefore did not have good contact over a large surface area, or else one or both sides of the connection offered high resistance because of dirt or corrosion that prevented electricity from flowing across the entire contact area. When normal electrical flow is concentrated in a small area of the plug, it works just like overcurrent situations but on a smaller scale and generates heat as a point source.

All contacts, both male and female, should be clean, free of corrosion, and dry. It's a quick check. Just eyeball the prongs and the receptacle every time you use the generator. Cables should be good for years of service. If they are dirty and corroded, you need a drier, cleaner place to store them. What about the cover of the receptacle on your boat? Does it keep the female plug clean and dry?
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post #3 of 3 Old 08-18-2012
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Re: Melting Marinco plug on my Honda EB3000 generator.

Any sign of burning, melting, or discoloration around the contacts on 30A Marinco connections means that one or both of the connectors should be replaced!

The problem can occur for several reasons:

1. The 30A connectors can't really take 30A continuous current. They are an old and terrible design, and should never be loaded more than 23-25A continuous. The Freedom 20 has a max draw of 21A, but Xantrex chargers have a high PF loss and draw could be higher. And, you can't run anything else while you're running the Freedom 20 with the batteries low, or you'll severely overload the connectors.

2. As noted above, connectors need to be kept very clean and tight. Care should be taken to ensure that the pins fully engage, and the plug is twisted to "lock".

3. "Copper creep" can happen as well, so periodically it is a good idea to take the connectors apart if you can and tighten the screw clamps on the three AWG10 cable connections. For molded connections this isn't possible, and the cord needs to be replaced, or the ends cut off and fitted with new connectors.

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