Receptacle Roundup VII: Miscellaneous NEMA 6

Well, odds are you won’t pull up to these outlets without you actively trying.  But this is Receptacle Roundup, not Receptacle Slipthrough.

L to R: NEMA 6-30, 6-50, L6-20, L6-30

L to R: NEMA 6-30, 6-50, L6-20, L6-30

There are two oddball sockets remaining in the NEMA 6-x series, higher-powered but much rarer.  6-30 delivers 30 amps of current at 240 volts, and 6-50 gives, well, 50A.  Both are for equipment and large power tools rarely seen in the home.  Those are both straight-blade standards; an “L” prefix in L6-20 and L6-30 denotes Twist-LokTM connectors, usually seen in industry.

6-30 is sometimes seen for big air conditioners- but not often.  The issue here is that really big loads don’t move much and should be hardwired into the building, while small loads want to use the common plugs.  6-30 then, isn’t the nice Mama Bear, it’s a neglected middle child.  Most homes have either central air, hardwired, or window units, with the smaller plugs.  By the way, it superficially resembles NEMA 6-15 but can’t be inserted mistakenly.  If you bring one plug anywhere near the other outlet, it becomes obvious they won’t go.  6-30 is enormous by comparison.

6-50 is also rare; the application it seems to have settled into is powering arc welders.  There are plausible reasons why someone would move a big tool around, specifically a welder, yet this tool needs ferocious power.  Since 240V is as much voltage as most general sites get, that means high currents.  If you find a 6-50 in your home, it’s because a previous owner geeked out on tools.  Again, it resembles a more-common plug (NEMA 5-15) at first, but it’s actually huge, and can’t be cross-fit accidentally.

The locking connector standards, on paper, don’t seem that applicable to vehicle charging.  Most EVs have some sort of programmed lockout, preventing driveaways while plugged in.  In any case, the little tabs on the plugs are not going to withstand motorcycle torques, let alone some of the bigger electric cars.  And yet, there are advantages.  You’re more likely to see L6-20 or L6-30, since industrial users want locking plugs.  The penalty of accidentally shutting down work equipment can be high, and industrial sites have carts and forklifts that can accidentally snag cables.  Since industrial users like them, L-connectors are more common than you might expect, and also tend to be well-built.  That’s hardly a guarantee, of course.  If road vehicles suddenly adopt these, manufacturers might sell skimpy units.

That’s road vehicles, then.  One application that took to L6-x is marina connections- the literal “shore power.”  RV parks don’t offer locking plugs much, I guess since an RV would still rip a plug out either way.  Boats, on the other hand, might bob at their moorings a significant amount without being adrift.  Another application is server rooms, with racks of servers, so their online services won’t drop out.  An L-plug goes from the wall, to the power hubs in the racks; the individual computers may tap into the hubs using standard NEMA 5-x plugs, or possibly smaller L-plugs for the heavy-duty units.

L6-x is common enough to have attracted some EV support already.  The Y-cords, used to create 240V power from two 120V outlets, typically end with an L6-20R on the last leg of the Y.  Possibly related, the 240V upgrade (for vehicle connectors originally sold as 120V) ends in an L6-20P.  You’re expected to buy adapters for various outlets, to L6-20.  These adapters and pigtails existed already, for industrial equipment.  But if you do the Y-cord trick, you can plug the upgraded vehicle cord directly into your Y.

L-plugs might be sturdier, but not to the level of SAE J1772.  Nor are any of the above plugs weatherized (other than optional GFI).  Marinas and boaters simply slip a rubber boot over the plug end, while the marina end may have a door that lowers over the receptacle and plug.  As with RV parks, the door inherently sheds rain downward, away from the connectors and cables.  And yet, neither marinas nor RV parks are deathtraps (the occasional B-movie aside).  This, despite RVs being outside… and boats, in salt water.

Similarly, all these plugs use “ground” as their neutral (return) line.  There is no true ground to act as a safe discharge, as current is already being carried there.  A lot of current.  All these use the same wiring (+120V, -120V, neutral/ground), which is why they’re all called NEMA 6-x.  The household 14-30 and 14-50 standards were given separate grounds and neutrals when they were revised in the ’90s.  And yet, these 6-x connectors have persisted for decades, without being withdrawn by builders, contractors, or NEMA itself, and without a notable death toll.  SAE J1772 also uses 120/120/neutral with no true ground, though of course it has additional safety features.

If you encounter any of these receptacles, well, more power to you (literally and figuratively).  However, I wouldn’t go preparing for N6-x charging capability unless I knew ahead of time that one of these outlets would be present somewhere.  I certainly wouldn’t install one of these, unless I knew there was some kind of circumstance already.  There are other, competing connectors that are as good as these or better.

NEMA 6-30/-50 Plus
-Existing standard like NEMA 5-15
-Cheap to purchase, installs just like existing NEMA 6-15 or -20
-More power than standard 5-15
-240V, which is preferable for car charging
-Designed to avoid confusion with other connectors

Minus
-Rare
-240V technically riskier than 120V
-Direct plugging (wall-to-vehicle) at 240V technically violates electrical codes
-No true ground; use of ground line as neutral is less safe
-Multi-hour charging still not fast enough for highway stops

Neutral
-A billion people use 240V every day
-Not any more (or less) weather- and vandal-proof than 5-15
-SAE J1772 doesn’t have separate ground and neutral, either
-May actually be more power than many vehicles can accept
-240V not strictly necessary for 2-wheelers
-Plugs getting a bit large (more a problem on two wheels)

NEMA L6-20/-30 Plus
-Existing standard like NEMA 5-15
-Cheap to purchase, installs just like existing NEMA 6-15 or -20
-More power than standard NEMA 5-15
-240V, which is preferable for car charging
-Already found in industrial applications
-Some EV support already, from accessory vendors
-Usually built to higher standards than non-locking connectors

Minus
-Still not seen curbside, for EVs
-240V technically risker than 120V
-Direct plugging (wall-to-vehicle) at 240V technically violates electrical codes
-No true ground; use of ground line as neutral is less safe
-Multi-hour charging still not fast enough for highway stops
-Unusual round connectors may look similar to the untrained

Neutral
-A billion people use 240V every day
-Not any more (or less) weather- and vandal-proof than 5-15
-SAE J1772 doesn’t have separate ground and neutral, either
-May actually be more power than many vehicles can accept
-240V not strictly necessary for 2-wheelers
-Plugs getting a bit large (more a problem on two wheels)

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2 thoughts on “Receptacle Roundup VII: Miscellaneous NEMA 6

  1. Pingback: Receptacle Roundup IXa: Tesla Roadster | cableflux

  2. Pingback: Receptacle Roundup X: SmartPlug/EEL | cableflux

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