This was the second incident of a shore power cable fire I personally saw this season. The first one was on a friend's Egg (Glory). The cable connector burnt itself beyond recognition (probably water intrusion); the second is what I am about to describe here. I took the above photo while I was at the Montauk Yacht Club on Sept 16, 2001. The photo was taken of the 50 AMP shore power cable on an older 40' Uniflight Aft Cabin Motor Yacht docked at her seasonal berth. No one was on board when the fire occurred over the weekend. I believe there were at least two factors that led to this fire; receptacle location, and, poor maintenance. I will attempt to explain how, in my opinion, this fire occurred.

Location: The poor location of the shore power receptacle; on the starboard side, aft, outboard was the main cause of the fire. A proper shore power connection is made when the plug is inserted and slightly twisted to make contact, but the contact is maintained when proper support of the plug in the receptacle is made by the plastic screw ring. I could not see a support ring when I took this photo. (It might have melted away, but my guess is…that it previously broke, and since it was hard to screw on while hanging over the side, it was never replaced.) As you look at the photo, try to visualize how you would maintain good plug-to-receptacle contact on this boat. The piling shown in the photo might have contributed to the cause. The dock is fixed (no finger pier) and the boat is able to ride up and down with the tide, wind, and wakes possibly dislodging the plug causing a poor connection. Note the space between the plug and the boat's connector. This plug was not touched before the photo was taken. (Although I did disconnect the other end on the pier before I notified the marina and took the picture.) Poor Maintenance: By locating the shore power connector over the side, it is an area that is impossible to maintain especially since there is no finger pier. The maintenance should consist of keeping this area free of salt and moisture that cause corrosion. Keep in mind that whenever saltwater evaporates, it leaves the salt behind. Later, just humidity causes the normally insulated surfaces to become conductive. A slow trickle of currant at first, then as the surface gets hot and burnt, carbon tracking occurs. The whole plug becomes a conductor and heat between prongs cause a fire. You are probably wondering why the circuit breaker didn't trip. Well, my guess is that as the above scenario played out, the trickle current wasn't high enough at first to trip the breaker. But 49 amps tracking across the normally insulated plug surfaces between the prongs for a period of time started it to burn.

Lessons to be learned; here are a few that come to mind:

1. Each time you connect or disconnect the shore power cable, look at both ends for signs of discoloration (overheating), corrosion, or bent prongs including the permanent connector on the pier. When signs appear, get it repaired before reconnecting.
2. Always use the plastic screw ring (female end) whenever the connector is connected to the receptacle. On the male end, that usually doesn't have a plastic screw ring, use an external strain relief (short piece of rope) to prevent the weight of the cord or careless people from slightly dislodging the plug.

 

3. In looking at the above photo, imagine water (dew) running down the power cable and into the end of the plug. You can see from the sharp bend that the seal was compromised and probably contributed to the cause of the fire. So, make sure there is a good seal on both ends of each connection. Water intrusion (salt) is a major cause of shore power cable fires.
4. Clean both plug surfaces with alcohol and a cotton swab to remove accumulate salt and corrosion. (BE SURE TO DISCONNECT BOTH ENDS OF THE CABLE BEFORE START OF WORK). DO NOT WORK ON THE SHORE POWER PLUG RECEPTACLE ON THE PIER. If it looks poor (signs of melting around the male prongs), notify the marina to have it replaced. It has ruined your shore power cord (plug); you will have to replace your cord because of their connector.

5. Before storage, spray with a moisture dispersing spray to minimize corrosion while stored. Also, keep the connectors plugged into each other to ensure that they are not damaged and to minimize exposure to the environment.

In closing, in my opinion, aside from the careless attention to spilled gasoline, and since your shore power cord passes so much power and receives so little attention, the power cord is "an accident waiting to happen" on each of our boat's. Mainly because they receive no maintenance from boater's, they have a very high failure rate. So beware.

Submitted by:

Joe Impellizeri

Sand Dollar

If you desire, send email comments to: Impeljr@aol.com.