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Old 05-11-2016, 05:06   #1
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Shorepower meltdown.....

Can someone give me some ideas of how this would have happened to my shorepower plug. Several months ago the same thing happened on the dock side. I replaced the plug. But this looks even more concerning.

Thanks
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Old 05-11-2016, 05:12   #2
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Re: Shorepower meltdown.....

Resistance causes heat. Bad or corroded connections cause resistance. Let's see how many words others can use to expand the above concept.
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Old 05-11-2016, 05:14   #3
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Re: Shorepower meltdown.....

Sorry went to stupidland on getting the picture attached.
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Old 05-11-2016, 05:15   #4
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Re: Shorepower meltdown.....

Quote:
Originally Posted by Geek_Guy View Post
Can someone give me some ideas of how this would have happened to my shorepower plug. Several months ago the same thing happened on the dock side. I replaced the plug. But this looks even more concerning.

Thanks
No photo.not enough info
but wildass guess from what you say .... you have replaced the ends on an old cord that is overheating. get a new cord
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Old 05-11-2016, 05:51   #5
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Re: Shorepower meltdown.....

Quote:
Originally Posted by Geek_Guy View Post
Can someone give me some ideas of how this would have happened to my shorepower plug. Several months ago the same thing happened on the dock side. I replaced the plug. But this looks even more concerning.

Thanks
The simple answer is: Bad connection = High resistance = Heat

Your burnt boat end here likely "looked ok", but caused the dock end to go south... Then fully toasted after you replaced the dock end... Kinda like patching a leaky garden hose with duct tape... The next "worst hole" is going to leak more...

Perfect candidate for a smart plug retrofit... Your boat receptacle is toasted, and is likely going to fry another boat end OR new cord in short order...

https://www.amazon.com/SmartPlug-B30...b_title_sports
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Old 05-11-2016, 05:56   #6
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Re: Shorepower meltdown.....

Quote:
Originally Posted by Geek_Guy View Post
Sorry went to stupidland on getting the picture attached.
As others have said, corrosion is the culprit. Corrosion causes the surface of the blades in the connection to become irregular such that contact is only made in a tiny area. With all the amps trying to get through that tiny contact area, resistance generates heat which exacerbates the situation. Changing the plug alone will not solve the matter once the receptacle has been damaged as the contact surfaces within will have eroded. One must replace both the plug and the receptacle. With that, and by giving the blades of the plug a periodic coating of "NoOx" or similar grease, one can prevent corrosion due to the blade's unavoidable exposure to moist, sometimes salty, air. On our boat, I periodically pull the plug, wipe the blades clean give them a good shot of WD-40, wipe again and then polish the individual blades with a bit of 800 grit Emory cloth before recoating with NoOx.

FWIW...
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Old 05-11-2016, 06:05   #7
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Re: Shorepower meltdown.....

Yes, as others have said corrosion can create high resistance, high temps, and burning. But, that's not the whole story.

The ubiquitous 30A marine connectors are a very old design and cannot reliably handle a 30A continuous load. They're really rated for around 24A. If you try to pull more than that and if the connections are not shiny and perfectly clean and mated, you're gonna have a meltdown.

Additionally, the wire connections inside the connectors suffer from "copper creep", and need to be tightened periodically.

Over the years I've seen literally dozens of such meltdowns in my marina and in client's marinas.

To prevent them:

1. be sure your connectors -- and those on your boat and on the dock pedestal -- are clean and tight; and

2. be careful not to run continuous loads more than about 24-25A.

Bill
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Old 05-11-2016, 06:35   #8
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Re: Shorepower meltdown.....

^^^^^ ^^^^^
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Old 05-11-2016, 06:51   #9
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Re: Shorepower meltdown.....

The previous posts got the answer but to elaborate just a bit.

- The overheating definitely due to a bad connection, 99.99% certain due to corrosion.

- When you have this problem you can't just replace the receptacle or the cord (or the plug on the cord) you have to replace both.

- 100% you need to upgrade to the Smartplug but NOTE: due to what's on the dock you can only upgrade the receptacle on the boat and the plug on the end of the dock cord that plugs into the boat. Smartplug sells a cord configured this way or you can just replace the boat side plug on your existing shore power cord if it's otherwise in good condition. Guarantee this will solve at least the boat side of the problem and if there is a problem it will be on the dock and not on your boat.
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Old 05-11-2016, 06:53   #10
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Re: Shorepower meltdown.....

I had this happenand replaced twist lock with Smart Plug.

Look to this article by Maine Sail.

http://www.pbase.com/mainecruising/installing_a_smart_plug

Rob
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Old 05-11-2016, 07:39   #11
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Re: Shorepower meltdown.....

failure to twist lock the plugs can do this. must twist the plugs in socket to lock them.
9 times out of 10, this is the case, a s folks donot realize the plugs have a twist locking mechanism for completion of the circuit.
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Old 05-11-2016, 08:16   #12
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Shorepower meltdown.....

Whether you go with a Smart plug or not, be sure the blades are clean and keep them greased with silicone or another grease to prevent corrosion.
I went with a Smart Plug as if the Dock pedestal catches fire I won't be happy, but if the boat does, I'll be a bit more upset.
Usually this kind of thing happens either in mid Summer where I am as that is when current is highest. Did you just start using heat?
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Old 05-11-2016, 08:18   #13
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Shorepower meltdown.....

What sold me more than anything on the Smart plug is its thermal disconnect, if it gets hot, it disconnects power prior to burning up.
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Old 05-11-2016, 09:01   #14
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Re: Shorepower meltdown.....

Besides replacing the plug, if the wires are black and not shiney copper the wires are also corroded. I had to cut 6 feet of the cord, last time I replaced the end. As others said they are really a 20 amp cord with short (very short) duration for 30 amps.

So you can't run a water heater, an electric heater and battery charger, etc all at the same time.
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Old 05-11-2016, 09:38   #15
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Re: Shorepower meltdown.....

As previously mentioned, corrosion causes resistance which causes heat.
What was NOT mentioned is heat causes further resistance, which causes further heat.

I bet you can guess where that leads...
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