Game Changer

This new SmartPlug

is just that

A recent Boat U.S. marine insurance report stated 11 percent of their fire related claims originated within the vessel’s AC power system, with the majority of these occurring at the boat’s shore power inlet. To address this and other shortcomings of the standard twist-type AC shore power plug and inlet, SmartPlug Systems, LLC has developed a new shore power delivery system that may set a new industry standard.

Rear view of the disassembled plug showing the unique internal cord strain relief clamp.

Barring failure of some owner-installed MacGyverism, overheating due to loose or corroded connections is the primary cause of shore power component failure. Corrosion in the standard twist-type connection typically occurs due to moisture entry at the plug/inlet connection, while arcing (which in turn leads to pitting, scorching and heat build-up) can be attributed in part to the shape and small contact area of the connector pins.
Another factor is the movement associated with a loose plug connection, a problem that can be exacerbated by tripping or stepping on the cord or vessel movement while at the dock.
SmartPlug engineers have devised a four-stage approach to defend against overheating. A new sleeve design and plug-to-receptacle locking system ensures the body of the plug (rather than the pins) bears the weight or tension of the cord, reducing movement and a tendency to work free.  To reduce arcing and corrosion, pin contact area is increased by more than 20 times and protected by three weatherproof seals.
Finally (and perhaps best of all) the inlet contains a built in thermal overload that automatically cuts power if the connector reaches 200˚F and restores it when the temperature drops to 120˚F, a feature that I find is worth the price.
The company’s 30-amp inlet and connector retrofit kit sells for $225.00, fairly reasonable when considering the features provided by the SmartPlug. A 50-amp inlet and connector, as well as cordsets, are in development for summer 2010 release.

Installation

To install the new plug, simply cut off the existing cord plug and wire the new SmartPlug as per the provided directions, or hire a certified marine electrician. The direction sheet for both plug and inlet are simple and contain photos (the company’s website also has handy installation videos). You’ll need a wire stripper or wire-stripping pliers and a Phillips-head screwdriver. Disconnect power at both ends before beginning and make sure your internal connecting wire is in good condition–a bright copper color.
The plug is fitted with color-coded terminals. Insert the matching wire until its insulation butts up against the plastic of the connector.
The SmartPlug inlet is designed to fit the same opening and screw hole footprint as the existing twist lock inlet on your boat with little or no modification required. I had to do some minor trim work and re-drill two screw holes, but this was likely due to the make and age (1970s-vintage Taiwanese sailboat) of the inlet. Make sure you use the rear mounting gasket and seal the screw holes with caulk.

Pros, cons, and observations

The SmartPlug is a well-built unit. All external metals are marine-grade 316 stainless steel, the electrical pins are nickel-plated brass, and the plastics are constructed of UV and heat resistant Valox 553U resins.
The straight pin design of the SmartPlug eliminates fumbling about in he dark to get the plug in. Push the plug (which only goes in one way) straight in until the side levers ‘click’ and then snap the locking cap down to lock it in place. The plug also incorporates a very clever internal cord strain relief clamp.
As to the cons associated with the SmartPlug system, even with one installed on your vessel, a twist-type plug (or adaptor) will be required to connect to shore power when cruising. Although this isn’t a clean break from the twist-type connections, it does provide the benefits of the new system at the vessel end. If you own the dock, a 30-amp dockside outlet can retrofit your existing pedestal.
From a design standpoint, the only issue I really have is that the length of the plug body coupled with the placement of the release tabs doesn’t provide the best grip while un-plugging–your hand tends to slide down to the cable when pulling.
I thought that including a power indicating LED would be a neat feature. Mentioning this to the manufacturer’s rep at the Miami boat show, he indicated it was in the works.
The SmartPlug is a well-designed unit that offers a number of improvements over the twist-type AC plug, however attempting to replace a system so firmly entrenched is a daunting task. In my opinion, the additional safety features and increased weatherproofing alone provide incentive enough to upgrade.