According to multiple reports, most AC electrical fires occur at the boats shorepower inlet. To address this and other shortcomings of the standard twist-type boatside connection, SmartPlug Systems developed a new AC shorepower system that the company hopes will become the new marine standard.
Loose and corroded connections are most often the culprits when overheating occurs. Corrosion typically results when moisture gets in at the plug-inlet connection, while arcing-which in turn leads to pitting, scorching, and heat build-up-is partially due to the shape and small contact area of the connector pins.
Photos by Frank Lanier
SmartPlug engineers have devised a four-stage approach that addresses these issues and protects against overheating. The SmartPlug system can be retrofitted to an existing shorepower cords boat end. The new sleeve design and multi-point plug-to-receptacle locking system ensures that the body of the plug rather than the pins bears the weight or tension of the cord, reducing movement and loosening. To alleviate arcing and corrosion, the pin contact area is increased by more than 20 times a standard plug, and it is protected by three weatherproof seals.
The SmartPlug inlet also features a built-in thermal overload sensor that automatically cuts power when the connector reaches 200 degrees. Power is restored when the temperature drops to 120 degrees.
The SmartPlug is a well-built unit that carries a limited seven-year warranty. All external metals are marine-grade 316 stainless steel, the electrical pins are nickel-plated brass, and the plastics are made of UV- and heat-resistant Valox 553U resins.
The companys 30-amp inlet and connector retrofit kit sells for $225-a bit expensive, in our opinion, but reasonable when compared to the $100-$200 cost of a standard outlet and plug, particularly considering the added safety and waterproofing features of the SmartPlug. The SmartPlug meets rigorous Underwriters Laboratory Marine requirements (as tested by IMANNA Labs) and the American Boat and Yacht Councils E-11 safety standard, according to the company. It also is Coast Guard compliant.
Installation
To retrofit an existing, standard shorepower cord, users can simply cut off the existing boatside plug and wire the new SmartPlug following the provided directions. The SmartPlug inlet is designed to fit the same opening and screw holes of the legacy twist-lock inlet with little or no modification required.
Testers found the directions clear and easy to follow, and the only tools needed for the project were a screwdriver and a knife or wirestrippers. Installing the adaptor kit was a relatively quick and painless job.
The companys website also offers a comprehensive installation video: www.smartplug.com/learn.html.
Pros and cons
Having to line up the pins on a standard twist-lock connector can be a pain-its a minor pain, but a pain nonetheless-particularly at night when the boat is docked in some unlit portion of a marina. The straight-pin design of the SmartPlug eliminates this annoyance. All you have to do is push in the plug (which only goes in one way) until the side levers sound an audible “click,” and then snap the locking cap down to lock it in place.
The most obvious drawback of the SmartPlug is that a twist-type plug (or adaptor) is still required to connect to shorepower at the shore side. Although the SmartPlug isn’t a clean break from the twist-type connections, it does provide some benefits, including thermal protection and increased weatherproofing at the boat end of the setup.
From a design standpoint, testers liked the clever internal cord-strain relief clamp, but we had a minor issue with the poor grip provided by the SmartPlug when unplugging. The length of the plug body and placement of the release tabs means that hands, particularly wet ones, tend to slide down to the cable when pulling unless care is used.
Bottom line
The SmartPlug is well-made and offers several improvements over the standard twist-type AC plug; however, attempting to replace a system so firmly entrenched in the industry is a tall order for any company. The additional safety features and increased weatherproofing alone will likely provide many sailors enough incentive to upgrade, but its too early in the game to predict how well it will ultimately be embraced by the boating and marina community.
My old shorepower plug and cord had both seen better days, so, after reading an article similar to this, I bought the complete Smart Plug system for my 36 year-old Newport 30 – Mkll. It took about twenty minutes to install, and I’ve been very happy with it. My only complaint is that it was quite a bit more expensive than a comparable generic system. Of course, years ago, I used to investigate companies that sold dangerously unsafe counterfeit electronic devices that regularly caused fires, so I’m always willing to pay for quality. The Smart Plug is built like a tank, and locks in with a satisfying “clack!”, unlike my old unit with the repeatedly bent-straight-again blades. A good system that I’d recommend.
Yes, the SmartPlug provides improved electrical safety, however in their earlier days, the electrical cords provided in the complete units were garbage.
I purchased mine back in 2014. If they were left laying in the rain on a flat surface such as a boat deck, they became covered in mold after a year or two. Scrub all you want, but the stains from the mold would not come off. Mine cord now looks like a diamond back rattler. I was informed by the manufacturer that all cords went that way and the matter was not open to discussion. My 15 YO Marinco cord looked nothing like that.
Not impressed with the manufacturer AT ALL.
I love the smart plug and installed the retrofit kit on my existing 30 amp cable. Yes, you still have the less efficient twist plug at the shore end and it might spark a bit an even heat up, but that kind of electrical activity is well away from me and my boat. I also use a 3 ft smart cable to connect my Honda 2200 generator.
I replaced the old Hubbell twist-lock plug on my powercord with the SmartPlug (and of course also replaced the socket/inlet) – straightforward and well worth it in my opinion – a much more solid connection than the twist-lock. I had misplaced the supplied fitting to slide the rubber cable boot onto the cable, but was able to jury-rig a solution. Also important is to fully seat the two parts of the plug together before installing the screws (don’t use the screws to pull the two parts together).
I purchased in 2018 , power indicator stopped working in 2020. Smartplug stated water most likly infiltrate the housing and shorted out the circuit. They would not honor there warranty, due to water intrusion. Not so waterproof.
Otherwise , easy to use.
Well, PS has again confirmed it has no clue when publishing technical information.
>>The SmartPlug inlet also features a built-in thermal overload sensor that automatically cuts power when the connector reaches 200 degrees. Power is restored when the temperature drops to 120 degrees.<<
No, no it doesn't. ABYC doesn't allow auto-resetting circuit breakers and the Smart Plug doesn't have one. Do the homework, PS.
I bought and installed the 30 amp end kit when they first came out ! Mine has the shut off when over heated. that was before it got approval from ABYC. the guy that runs the electrical dept of ABYC is the same guy that invented the Hubbell twist plug for the Navy almost 60 years ago. talked about conflict of interest. ABYC has blocked any products put forward (60years) to replace the twist plug, at the same time guaranteeing that Hubbel receives his rewards ;-(
If you look at the twist plug on the tabs of the make end, they holes in the tabs, and on the female end the tabs with a half ball that fits into that hole on the male end, that is the only contact that the plug makes, it is no wonder that they arc and cause fires. Running 30 amp through that 1/8″ ball is like hooking a welder to fibre optics !
Hubbel held up the approval of the Smart for years, and the only way that ABYC ( HUbbel) would accept it was if they removed the over temp shut off. his theory was that if the plug restarted up it might leave the end live for someone to touch, thinking it was dead. It has an LED to show weather it is live or dead ! For a good accessment of the Smart plug check out www, howtomarine.com
I have my cord hard wired in to my boat. I unplug from the dock and leave the cord on the deck of my boat. If there is a bad connection it will be on the dock not on my boat.
There we go!!! I don’t leave the cord on the deck, I feed it into the hollow area behind the cockpit wall and hang the plug on an eye bolt with a carabiner. I have a bit of an issue with the screw on access cover and will replace it with a hinged door access when I locate the right one.
I read that the ends of the shore power cables must be molded on. If you cut the old plug off and connect the new plug, it is not molded on. This could allow for water intrusion and corrosion which could start a fire. You should buy a new cable with the smart plug molded on.
Yes, we can all buy new complete molded shore power cables for (at least) hundreds – the vendors should make a living :)… Or we can seal the new plug sleeve along the cable and inside with 4200/5200 for less than $5.
It is interesting that the overheat problems usually occur at the boat end. The power pedestals on shore have more or less the same connectors. Perhaps the locking ring is missing or not tightened properly. It might help to have some strain relief so that the weight of the cord in not applied to the connection and boat motion forces are not transmitted.
I apply dielectric (bulb) grease to the female sockets. So far, so good.
PS I second Bruce Weller’s comment. Aftermarket connectors are not waterproof.
I know my post isn’t going to change anything, but the American style shore power connectors design is prone to failures, no matter what is being used.
The socket contacts are poor at any case and do not provide an assured safe full surface to surface contacts, anyone can see it if opening the socket back side. The turning lock isn’t safe enough either as it can be left with less than a full turn.
The water sealing arrangement isn’t any better on the long run either, especially when the sockets are installed out of the cockpit, in many situations, on the transom or external deck structures – exposed to the elements and accidental mechanical impact.
My European born (Contest, by Contest Yachts, NL) boat came with the standard DIN type 30 and 50 Amp (goes by plug sizes up to 600A) – now IEC 60309-5 and IEC 60309-2 IP-67 water sealed standard for marine shore power boat inlet and shore power cable plugs and inlets – all are fully protected inside a cockpit dry compartment. I’m more than happy my (Boston) marina also provide such optional sockets on the shore power pedestals. Cruising worldwide, I have not yet seen better and safer shore power connectors.
And I’m not even speaking about the price comparisons, where the DIN/IEC components costs are about 80% lower.
The “SmartPlug” is almost certainly a safer and more reliable off-the-shelf design. My issue is the proprietary design on what should be an open standard. If the devices gain widespread use then the market will drive the cost even higher. I cannot support unchecked competition. Maintaining vigilance on my existing legacy connectors with the understanding that they are prone to failure with catastrophic consequences, not much different than, say, a shaft seal. or consider a future upgrade to an international connector as described by Nitzan, above.