Bzzzzzzzztt!!!

That's the sound I heard outside my boat at about 9 PM Friday night as the AC power went completely dead. My first thought was, "I hope my fire extinguishers all work..." I grabbed a flashlight and went out to check the shore power box.

My shore power cord had shorted out. Wasn't cut or anything, just old age. The insulation on the individual wires had broken down. I found a lump further down the cord from the short and cut it open to see what it looked like. Here are the pics:



The part that concerned me was the breaker on the dock box did not trip. Wondering why...

Oh My...

Oh My, considering I know my Marinco shore power cord is 11 years old this month, I think I will be getting a new one. Thanks Mark, glad it didn't turn out worse.

Scary

Good thing you were there!

Yikes! No idea how old mine is - came with the boat. And several of the old zombie boats on the dock have cords like that disappearing into the tarps. The chances that anyone would be there to witness a stochastic zott seem remote.
I wonder if that could have been caused or accelerated by some past stress, such as a yanking event on the cord... ?

My guess would be a chronic bend in the chord. Especially coming in that location.

I routed this scary thread and pictures over to a very well regarded surveyor that I know.
Her comment:

"Thanks for sharing that. Way too common!
The breakers seldom trip because the arcing typically keeps building heat and increasing resistance as the heat builds. I have seen bilge pump wiring completely flash off the insulation due to rotor lock and the ammeter showed a current flow of less than 3 amps! "

Yikes.
Perhaps it's good to replace our ancient shore power cords...
:0

Loren

Now I'm worryuing about my bilge pump wiring...

I wonder if that could have been caused or accelerated by some past stress, such as a yanking event on the cord...?

Click to expand...

I couldn’t see any evidence of stress, like sharp bending or abrasion, of any kind. My theory is that it was just age-related (sun/weather exposure) and maybe some moisture intrusion due to breakdown of the outer insulation or through the connector somehow. The 2” piece that I cut open showed deterioration of the fiber strands that run alongside the conductors, crumbling of the conductor insulation and evidence of the “black wire” type of corrosion I have seen on other un-tinned wire.

Basically I think the insulation on the conductors deteriorated to the point where it allowed an arc to occur.

This cord also came with my boat 5 years ago, and was likely in use for at least 5 years prior to that. Seeing what the inside of the cord looked like convinced me to never buy a used shore power cord at a swap meet...