Shore power cords make an important and often unrecognized contribution to boating convenience. These flexible power cords make the connection between marina utilities and your vessel's power distribution system. Improper use and poor maintenance can cause serious injury or death, damage to vessels and unplanned repair costs.
Two of the most popular flavors of shore power are 30 ampere 125 volt (NEMA L5-30) and 50 ampere 125/250 volt (NEMA SS-2) terminal configurations. Overall, there are five receptacle and connector systems approved by the National Electrical Manufacturers Association (NEMA) for marine use. Plug terminal arrangements between the different systems vary in radius and terminal shape. They are designed to avoid mix ups between different types of plugs. The basic concept is to not force a plug into a receptacle. As long as the L-shape terminals of marine shore power plugs remain unaltered, it is hard to plug your boat into the wrong type of shore power. Forcing a modified 30 ampere 125 volt plug into a 50 ampere 125/250 volt receptacle can produce disastrous results.
Forcing the wrong type of shore power plug into a receptacle or using a makeshift plug can inadvertently allow current to enter the water. Alternating current leakage into the water will often not open protective circuit breakers and will endanger swimmers in the water and cause damage from electrolytic corrosion. Current leaking into salt water poses less of a problem that the same current being discharged into fresh water. Salt water is conductive and will carry current to earth ground. Fresh water is a poor conductor and leaking current will set up an electrical field around a vessel that is dangerous to swimmers. An amazingly small amount of current can paralyze a swimmer and cause drowning.
Observing shore power cord walking the docks at most marinas will turn up some truly nonstandard configurations. Here are some simple safety practices that should be applied to your vessel's shore power cord:
- Purchase a shore power cord that is UL-Marine listed
- Avoid using household or outdoor electrical extension cords to provide power to your boat
- Shore power plugs and receptacles have L-shaped or locking terminals. Be sure to twist the plug into the receptacle until it is fully locked into place
- The male end plug of a shore power cord should be molded on or have a weather proof seal in place to keep water out of the internal electrical connections
- Avoid the use of adapters. If an adapters is warranted, place it on the shore side of the cord connection
- Turn off the main circuit breakers on the dockside and vessel electrical distribution systems before plugging the shore power cord in between them
- Plug the female end of the shore power cord into the boat first and then the dockside pedestal. Reverse the sequence to disconnect them
- Avoid leaving a shore power cord plugged into the dockside power pedestal with the boat end unconnected. The free end can be accidentally kicked into the water creating a hazardous situation
- Check your shore power cord for cuts, exposed conductors, breaks, nicks, burnt plug or receptacle terminals, bent or broken plug blades, and corrosion
- Avoid coiling a shore power tightly on the dock, lay it out loosely or hang it up
- Keep electrical shore power cord connections clean. Use a corrosion inhibitor and cleaning product like LPS 1 greaseless lubricant monthly. Avoid products like WD-40 that leave a current resistant film on the cord contacts
- Shore power cords should not be spliced or have taps made into them
Shore power cords are simple to use and uncomplicated. A little care and caution will prolong their useful life and provide safe electrical service to your vessel.
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