A Tight Connection

Photos by Chris Hemer

SmartPlug’s replacement for standard RV and marine shorepower cordsets and receptacles improves safety and convenience

When I was a fulltime RVer back in the early 2000’s, I remember the power in my motorhome began flashing and finally “blinked” out on a hot day while I was working on my computer and running the air-conditioner. Looking around for the issue, I glanced out a window and saw some smoke. There was no fire pit in the general vicinity so it quickly became evident that the smoke was coming from my rig or the one in the site next door.

As it turned out, the plug on the motorhome’s cordset melted and was smoking. No flames, fortunately, but the burnt and discolored plug was an uncomfortable sight. The cause of this failure, which I have seen many times as a technician and again on another personal RV, was resistive heating.

As seen in this comparison between the typical pins on a twist-lock (left) versus the SmartPlug (right), the SmartPlug establishes greater contact to maximize electrical transfer — the company claims a 20x improvement.

This thermal image of a SmartPlug and a typical twist-lock under load is quite telling. According to Smart Plug systems, the SmartPlug protects against overheating through its sleeve design and locking system, while its weatherproof seals maintain a dry connection. There’s still a fair amount of play with a typical twist-lock connection, which can lead to arcing. Photo: Smart Plug

The SmartPlug is very different from power cords that use twist-lock connections. First is the form factor: Instead of twisting in to secure the connection and then securing a fine-threaded (and fragile) plastic ring, SmartPlug just pushes straight in and locks itself in place using spring locks on either side. This reduces the wear on the pins inside the connection, keeping the connection tight without movement. Twist-lock connections also can become loose, weakening the connection, which can be the result of a plastic ring that does not keep the whole thing together — a common issue with 30- and 50-amp connectors.

Second, SmartPlug uses much heavier-grade pins that are also larger, providing a tighter connection. This upgrade by itself can reduce or even eliminate resistive heating.

Third, the SmartPlug connection is gasketed and, therefore, watertight — again, eliminating the corrosion that contributes to resistive heating. The system includes a snap-on protective cover on a lanyard to guard against moisture and damage to the open end of the cordset when not connected to the RV. Once closed, the SmartPlug receptacle on the RV is also watertight.

Fourth, the latest version also includes a second LED on the cordset plug that indicates shorepower polarity — which helps indicate whether you have a safe connection.

The SmartPlug is available in 30- and 50-amp versions as a replacement cordset end and RV side receptacle for existing cables, or as a complete cordset with easy-pull shorepower plug and softer insulation jacket that doesn’t stiffen in cold weather. Anyone who has had to deal with a standard 50-amp cord will appreciate the flexibility of the Smart Plug cable. In fact, RV Enthusiast Publisher Bob Livingston has been using the Smart Plug cordset for a number of years and said the difference is dramatic, especially in cold weather.

Kits start under $150 and go up from there. Expect to spend $400+ for the 50-amp cable and hardware kit in chrome. We installed a chrome SmartPlug 50-amp system on a 2015 Montana fifth-wheel, replacing a legacy twist-lock which, as it turned out, was broken inside from an over-torqued set screw.

Once disassembled, a broken screw for the L1 hot leg was identified. There was also a stray wire sticking out of the neutral terminal.

The unit is secured to the wall with user-provided screws. The holes lined up perfectly in this case, but may not always. The old gasket had discolored the fiberglass, but most of the area was covered up by the new receptacle.

The Smart Plug includes a reverse polarity LED on the connector, which can help prevent damage to to electric appliances and accessories.