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What you
should know about
Shore Power Connectors
Fires that occur at the dock are often caused by shore power connections. High resistance at the connector, coupled with a steady load over a long enough period of time can create significant heat. This increases the resistance even further. Eventually, a high enough temperature is reached to melt the wire insulation and/or the plastic core of the shore power connector. Then it shorts, causing fire. The wires are already so hot and resistance is so high that even when they are shorted there may not be enough amperage flow to trip the shore side breaker. So current keeps flowing, feeding and spreading the fire deeper into your boat.
These are some of the conditions you can check for in your shore power connectors:
► Cord should not be run directly from the boat to the dock without being secured to the vessel. If they are, the plug will be tugged every time the vessel moves, resulting in damage to the connector. At the dock end, attach a string or other support to the cord near the connector to provide strain relief.
► Ideally, connectors should not be
located such that cords can be kicked or stepped on. If this is not the case on
your boat, and you cannot easily relocate the connectors, provide some means of
tying the cord down to the deck or to an adjacent rail or fitting so it won’t
be damaged by an inadvertent kick – as well as to protect the inadvertent
kicker!
► Side to side movement of the cord plug will stress the connector, and moisture entering the connection can allow corrosion to occur, increasing resistance, and causing heat/fire. To prevent this, every cord should have a securing nut, and it should always be tightened when hooking up.
► Improperly tightened screws attaching the wiring to the connector can cause an arc and generate heat.
► Failure to turn off any loads within the boat (such as a running electric heater, water heater or refrigerator) prior to plugging in or unplugging the cord can cause an arc, pitting the contacts. If this happens enough times a carbon film will form, creating a bad connection that will generate more heat.
► Like many other components, shore
power cables have a limited life and should be replaced well before they give out entirely. Just
plain age and corrosion can lead to resistance/arcing/heat.
The bottom line is to keep
the lock nuts tight, secure the cord to the vessel before running it to shore
and inspect the connector and the plug end every time it is connected or
disconnected. On connectors with white plastic centers, a little bit of
discoloration around a contact is a probable indication of much more serious
problems inside the connector. It’s better to err on the cautious side, and if
anything appears to be failing, replace the connector and the cord at the same time.