Receptacle Roundup X: SmartPlug/EEL

And now for something partially different: boat-marina connectors (literal shore power).

Boats are vehicles- they just happen to pitch and heave, in water, possibly salty.  When docked, they plug in; there’s no reason to fire up the engine to watch TV or cook.  There’s no sensible reason to fire up a generator, either, as grid power is more efficient than a small generator by a few times over.  In recent years, two new shore-power connectors have emerged: Smartplug and EEL (Easily Engaged Locking, from Marinco).  How did the watercraft industry handle their chance at a vehicle-specific connector?

p105044dSmartPlug goes straight in, unlike the existing NEMA Twist-LockTM standards.  The 120V, 3-prong model carries 30 amps, while the 240V uses 4 to carry 50A.  Both then have metal latches on the sides of the outer sleeve; the weather door on the receptacle side then folds down on the plug, forming a third latch.  Inside the outer sleeve is a rubber seal; the actual contacts are then recessed inside the inner body.

p105036dWhat’s the point of all this?  As before, recessed contacts keep your fingers out of there; the chances of rainwater getting in are also reduced.  The chances of you bending pins from abuse are close to zero.  A locking connection then reduces the chances of gapping and arcs due to wave action.  Arcs from bad connections cause heat, which causes smoked connectors and the occasional boat fire.  SmartPlug’s wide pins and slots further reduce the odds of gapping, and can take more heat if it somehow still occurs.  If it still heats up, the connection has a thermal switch to kill the power at a certain temperature.  Feeling safe yet?

Hmm, three prongs carrying 120V/30A, and four prongs carrying 240V/50A.  That sounds like… NEMA TT-30 and 14-50, used by RVs.  Boats are pretty much RVs that rock instead of roll, and have similar electrical devices and amenities.  Marinas, too, are pretty much RV parks that are always wet, instead of sometimes, and have similar customer demands.  Why wouldn’t their connectors bear similarities?

Marinco’s EEL is conceptually similar; there’s an increase in sealing throughout.  It’s still a twist-to-lock standard, though, and is backward-compatible with the existing equivalents (NEMA L5-x and L6-x).  For shore power, the NEMA Ls had a threaded outer collar for sealing.  Unskilled boaters could cross-thread the plastic collars, or… not bother to use the seal at all.  The key difference with EEL is that the sealing collar goes from threaded to clamshell, built-in, which is both faster and more intuitive than a separate, non-bayonet lock.  This clamshell helps shield the blades from abuse, but isn’t as extensive as SmartPlug’s sleeving.  EEL doesn’t have the bombproof pins or thermo-switch, either.

The boating industry has responded to these multiple innovations with a resounding… meh.  Marinas don’t particularly want to change their receptacles (at cost), and boaters feel no compulsion to upgrade with little marina support… since marinas feel little boater demand.  The designers weren’t stupid; EEL was kept backward compatible, so you could carry an EEL cord and still use “regular” marina pedestals.  Meanwhile, SmartPlug users can buy a cord with a SmartPlug end for their boat side, but a regular end for the dock side.  Then you won’t burn up your boat, though there’s still the risk of burning the marina pedestal.

Thus, I won’t declare these standards to be failures.  Insurance companies like them just fine, and may give you a discount for your diligence.  Like the Tesla Roadster connector, you can (and probably should) carry adapters anyway with these standards.  Boat owners already use Y-cables to adapt between L5-x and L6-x, and to tap multiple outlets.  The fact that a format war is technically going on simply means you have to double-check before hitting “add to cart.”

SmartPlug/EEL ground

You won’t find these standards on the highway, sure.  But you can go to a boating outlet and get them for your house.  You’ll enjoy the safety and rain benefits, particularly if you park your trailered boat in the driveway, too.


One thought on “Receptacle Roundup X: SmartPlug/EEL

  1. Pingback: Receptacle Roundup XIIb: Japanese Level 1 | cableflux

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