TECHNOLOGY
Courtesy of SmartPlug Systems LLC
The SmartPlug’s designers addressed all of the major and some
of the minor shortcomings of the twist-lock connector. With the
adoption of this new design, shorepower-connector-induced fires
could become a thing of the past.
plug. Recall that when the original twist-lock connector
was introduced, Franklin Roosevelt was president, a first-class postage stamp cost 3 cents, and federal spending was
a mere $6.8 billion. Ken believed the time was ripe for a
change in shorepower connectors.
The SmartPlug’s design and construction address
nearly every shortcoming of the old twist-lock connectors.
Most significantly, the SmartPlug does away with the
semicircular-shaped blades, as well as the twist-lock
design, which, while innovative in its day, is no longer
necessary to achieve a secure connection. Instead, the
SmartPlug utilizes straight blades whose contact areas
are significantly greater than those of the twist lock,
and, when the male plug is fully inserted in the female
receptacle, the two locking mechanisms automatically
engage. A unique sleeve design adds support to the
connection. Unlike the locking ring on the twist-lock
connector, it’s impossible to engage the SmartPlug’s locks
without full interface of the male and female components.
The straight blades have 20 times the contact area of the
curved, twist-lock blades. And they are so much more
efficient at conveying current that even when the 30-amp
plug was tested to 100 amps, there was no measurable
increase in heat generation.
With the SmartPlug design, water entry into the plug
and blade area is dealt with by utilizing a triple seal
arrangement. All of these seals are important; however,
the compressed face seal is especially significant, because
it prevents water from entering the blade contact area. If
water enters a shorepower connection when high current
is present—when air conditioners or water heaters are
operating, for instance—it nearly always causes high
resistance and excessive heat. Even if no current is present,
the long-term result is an accumulation of resistance-inducing corrosion. Add salt to the mix, and the process
is accelerated. The SmartPlug’s seals help to prevent
this; the twist-lock design incorporates no such seal.
All this talk of resistance and overheating may lead you
to wonder about preventative measures. Some expensive,
high-tech, whole-vessel monitoring systems incorporate
shorepower inlet temperature sensors, and at least one
company offers a less expensive, stand-alone option for
shore inlet temperature monitoring with an automatic
disconnect feature. But what message does this send?
Should monitoring and control systems really be
necessary for a simple receptacle? Because of its overrated
current-carrying ability, it’s unlikely the SmartPlug will
ever overheat, but if it does, the vessel-side receptacle
incorporates a thermostat that will break the connection.
The originator of the SmartPlug set out with one
mission in mind: to design and manufacture the safest,
most reliable shorepower connection system possible,
using only the finest materials. Not surprisingly, SmartPlugs
cost three to four times what twist-lock connectors cost.
But can you put a price on fire prevention?
As this was written, the SmartPlug was undergoing UL
Marine equivalency testing by IMANNA Laboratories, an
independent, USCG- and ABYC-recognized test facility.
The folks at SmartPlug Systems were confident they
would be awarded this prestigious seal of approval. In
addition, the company has been contacted by a well-known insurance carrier concerning possible discounts for
clients who opt to use SmartPlugs.
SmartPlug products can be adapted and retrofitted
to existing vessels and dock systems. So far, 15 marinas
have made a commitment to adopt the SmartPlug
system for their docks. A variety of 30-amp, 120-volt
SmartPlug components are available now, and a full line
of 50-amp, 120/240-volt products is scheduled for
release this summer.
As mentioned earlier, I’ve seen countless overheated,
burned, and charred shorepower connectors and at least
one boat destroyed by a fire caused by a shorepower
cord. It’s quite possible that such failures and fires will,
with the adoption of the SmartPlug system, become a
thing of the past.
Steve owns and operates Steve DA’ ntonio Marine Consulting
( www.stevedmarineconsulting.com), providing consulting
services to boat buyers, owners, and the marine industry.
