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Avast, ye scurvy dogs!
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Discussion Starter #1
Dearest Sailheads,

My shore power deck connection is fried. See pic.

Can anyone tell me how this could have happened? Shouldn't the dockside or onboard circuit breaker have tripped before the connection melted down?

It's 30 amp and 125 v and has been plugged into shore power for about half of the 5 years it's been installed.

Thanks in advance!

Ed
 

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Lucky you didn't lose the boat or worse!
 
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That kind of overheating is usually caused by loose or corroded connections, corroded plug prongs etc. If you look at your shore power cord you will probably see signs of overheating where the prongs enter the plastic plug.

The breaker isnt necessarily going to trip unless the amp draw exceeds the rating of the breaker, or the wire shorts to ground. Overheating can happen without drawing excessive current.

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It's a good idea to clean your prongs with a wire bruish, and spray socket and plug with something like DeOxit which lubricates and protects electrical connections.
 

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Consider yourself lucky, Probably bunged the end of the cord too. Happens frequently. Replace both units with the best most expensive new fangeled gizmos available. Dang the expense, there's a lot at stake. Somebody will clue you as to brand name.
 

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Your shore power plug is based on ancient, but accepted, technology. They fail often and are a leading cause of boat fires. You are lucky your whole boat didn't burn. Switching to a Smartplug would fix it.
 

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Dearest Sailheads,

My shore power deck connection is fried. See pic.

Can anyone tell me how this could have happened? Shouldn't the dockside or onboard circuit breaker have tripped before the connection melted down?

It's 30 amp and 125 v and has been plugged into shore power for about half of the 5 years it's been installed.

Thanks in advance!

Ed

How it could have happened? One of the conductors (prolly the ungrounded by the look of it) developed an "intermittent" connection, which then began to arc and create carbon, which continued to increase the "closed" circuit connection impedance. Eventually, the impedance and resultant voltage drop became high enough that for the load current, sufficient electrical energy was converted to heat, to melt and burn the plastic.

Why the breaker didn't trip? The total circuit impedance was low enough that the current through the high impedance connection, was lower than the breaker rating. In your case, the breaker would not trip if 30 A was sustained forever. However, if 50 Vac was dropped at the high impedance shore power connection, that's 1500 W, certainly way more than enough to melt plastic. Under normal circumstances the voltage drop across a shore power connection should be less than 1 Vac.

It is wise to check cords and connectors after every use for signs of discolouration. At first sign, investigate, as just a slight discolouration may be due to actual burning on the other side.

Also investigate any case of low AC Panel voltage reading. If it is normally 120 Vac, and today it is 108 Vac, ensure it is not because of a bad connection.

Shore power connectors have an ALF (Average Life Expectancy) of about 15 years, and cords about 5.
 

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The wire that shorted out(black) is very green with corrosion i would bet the receptacle either leaked between the hull or it is in a high condensation area. Was this marine grade tinned wire?
 

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Avast, ye scurvy dogs!
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Discussion Starter #10
Great stuff, folks. I really appreciate it. I'll add one more item to the "Inspect Regularly" list.

Thanks!

Ed
 
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