I've never come across a combo unit like this one... Coincidentally, I do have a couple old Hubbell duplexes that are a T-slot outlet combo with a configuration for the other outlet that looks similar to this one... Hubbell had all kinds of odd stuff back in the day!

-Randy

I don't know why Hubbell would make something like this with a...
/ \
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...slot configuration rated at 120V and 15A when there was already an accepted NEMA standard established for this. I found it at my old cottage in the boathouse. Maybe it was once used for some strange appliance. Anyone have any ideas?

[This message has been edited by MattE (edited 07-10-2004).]

Matt,
I've found these in some odd places... The Hubbell duplexes I described above were in an old 1900's house we razed the old system out of... Most common place I seem to find the single ones were in the FAU closet of old 1940's & 50's houses. My old elementary school I went to had some really strange stuff (Sierra Nema 5-15/6-15 duplexes in the bathrooms!) But each classroom had a single 5-15 recept & one of the style above in a 2G box.. always right next to the door.. & one step up of the same in the cafeteria.. I've no clue what the purpose of alot of things in that place was for!

-Randy

Here's the one of the Hubbell duplex's



edited to add image..

[This message has been edited by Lostazhell (edited 07-10-2004).]

MattE, that's quite a find. The “crowfoot”/parallel-blade all-in-one combination is curious, and as NEMA wiring devices go these days, looks like a combination of NEMA 1-15R and 10-20R, but these days, the 10-20R configuration is for ‘non-grounded’ 3-pole 3-wire 125/250V 20A service. Maybe a 1940s mutation for earlier 120V-grounded portable equipment? I think NEMA 5-15R and other “U-ground” devices were a mid-/late-1950s iteration.

The “small crowfoot” (NEMA 10-20R) illustration is…

At that time, differentiation between a current-carrying neutral and an equipment-ground conductor did not exist in wiring devices. Out west, 10-20R was the predecesor to 3-pin NEMA 6-15R/6-20R for grounded 240V, cord-connected window air conditioners starting in the mid 1950s. 240V {up to 3.8kW} portable electric heaters [probably as early as 1930-40s] typcailly used a NEMA 2-20R 2-pin 2-wire, NO-equipment-ground configuration, and occasionally 2-30R {up to 5.7kW.}




[This message has been edited by Bjarney (edited 07-11-2004).]

Had those on the farm. They were used in the barn where a standard 5-15 U-grounded recepticle would have been installed.
The farm was wired in 1952.

I have a collection of those, and have been using them for speaker connections at one time, and as 12VDC power.
Also, the plates for that particular one are identicle to the NEMA sigle recepticle.

Originally posted by Bjarney...


Now that you mention it, I think it might have been used for an older water pump that needed grounding. The boathouse where this was found is also where the pump has always been located. The cottage was wired in the late 40's. I guess this was some early design by Hubbell for equipment that needed grounding, but was forgotten once grounding became standard in the 60's.

Thanks to everyone who posted!

The "How & Why" of the different receptacle configurations is something I find quite fascinating.

On the pics elsewhere of receptacles with two T-slots (look like they'll accept a 1-15 or 2-15 plug), in what sort of locations and during what time period were these installed?

Scott,
In your posted diagram of the 10-20R specifications, what's that reference to an "Optional notch" all about?

Paul,
I've come across the T slot outlets more or less anyplace you could put an outlet in older homes dating from the late 1800's to about the early 1960's.. The house I grew up in was built in 1958, & peculiarly, all the switch controlled outlets were T slot, while the rest were standard Nema 1-15.. I've personally never come across one of the T-slots wired to 240V, even though some of them show a dual 120/240V rating.. I've also come across old 1-15 outlets which show 250V ratings!

Then there's the really odd versions that basically function the way a T-slot would...



I've only come across a handful of these..

-Randy

Paul, apparently it mates with the "10-20P" plug, but I have no idea what purpose it serves.

Randy--

those tandem-paralell recepticles, do you know what they would have been used for, ive got one up here in my room/office below a window cut into the baseboard, and it reads 240v, i was thinking it was for an old window ac or somthing along those lines, but the only dp breakers in my panel is for the range and dryer, and neither of those are tapped off anywhere along their run, or in the panel

thanks
Rob

Randy, I also have many old NEMA 1-15 recepts with a 240V rating, and one of those really odd ones which function just like the T-slot type. Something interesting about all of these old recepts with a dual rating is that they are rated for only 10A at 240V. So if one of these were wired for 240V then wouldn't it need a 10 amp fuse or breaker? Has anyone ever seen a 10 amp fuse in an old panel? (...most likely in a fuse block with 2 of these 10A fuses for the 240V.)

Another thought...

Maybe an old version of the NEC would solve the mysteries surrounding these old recepts, blade configurations and ratings. I know someone must have an old version of the NEC of Canadian electric code book.

Here’s a really strange old current tap. I found this in an antique mall last weekend here in Michigan and couldn’t resist it for $2.00! I collect pre-1900 light bulbs and other turn of the century electrical items and thought this would make a neat addition to the collection. If anyone could shed some light on the funky 4 prong pattern I would be interested in learning more about this thing. I thought it was the same pattern as the plugs shown elsewhere in this thread but I now see it’s a little different…

Tim Tromp
BulbCollector.com

Kilok—

30 seconds with an ohmmeter would answer a lot.

[Notice the tandem-blade pair is not aligned too well.]

Tim,
Nice find there I see what you're referring to as far as the slots not being aligned straight... but my guess would be it was intended to function at the outlets I posted earlier... As far as what that function would be, I'm guessing code wise, they weren't too particular about a 120V plug fitting a 240V outlet & vice versa.. & these outlets could be used for either! Is there any markings on this regarding manufacturer, ratings, etc?

Rob,
Even though you don't have a 2 pole breaker for the outlet, doesn't mean someone didn't connect it to both phases via 2 - 120V circuits someplace.. I'd test it with a meter to see what voltage is present..
The left outlet in the pic I posted is labeled "Magnus" "10A 250V" on the face.. but it was connected to 120V (the original service that I changed out was 30A 120V in that house!) Under a window in the baseboard, I'd make a wild assumption that it was an original general use outlet, since the baseboard is where they seemed to put all the outlets back in these days.. As far as for an A/C unit... I'd bet the extinction of this outlet style was likely some time before A/C was around...

Matt E.
We quite frequently use Nema 5-15 outlets rated for 15A 120V on circuits using 20A breakers.. Code allows this as long as there are more than 1 outlet.. (A duplex satisfies this) If you're only installing one single outlet on a 20A 120V circuit.. It must be Nema 5-20 per NEC 210.21(B)(1)
I'd love to get my hands on a wiring guide or some type of electrical code book from back in the era this stuff came from.. To think the code book back then was probably no thicker than an average magazine!

-Randy

Me too! I bet the codes were extremely simple, e.g.:

"Wire, for circuit conductors, shall be used."

"Fuses, for circuit protection, shall be permitted."

I could think of other ersatz codese but I'll spare the rest of the world.

There are some old configurations over this side of the Big Pond that might confuse current generations as well.

Here's an old adapter, or line-tap as you might call it:

pauluk,
How many different configurations are in that thing??? I'm guessing 3?

-Randy

A lot of the 'T' plugs & sockets similar to the NEMA 2-20 pattern have found their way onto caravans & campervans for 12VDC power. The packet for the plugs rates them as "32V @ 15A". These plugs are also rated for 110VDC. The words 'extra low voltage' are marked on the plugs, matching extension cord sockets & surface sockets.
There are a couple of other plugs that are a mystery to me. In Australia, one manufacturer (Clipsal) offers a 2 pin parallel plug the same as a NEMA 1-15P configuration. It is rated at 250VAC @ 10A. I guess this was for electric clocks that were connected onto lighting circuits. This plug does fit into a NEMA 5-15R socket.
The second mystery plug/socket combination are the 3 pin plugs with two round pins (for active & neutral) & a flat earth pin. These are rated at 110V @ 10A. These are also an Australian made device. How much 110V gear made it into Australian homes to warrant manufacture this pattern of connector?. (I can get photos if people are curious on these connectors)
Finally, I have measured a three pin socket to see if the ones used in Australia, New Zealand, New Guinea & other South Pacific countries are the same dimensions as the NEMA 10-20R shown in this post. The one pictured is bigger that our sockets in distance between pins & pin size.

Randy,

It's actually designed for the two different configurations (grounding and non-grounding) of our old 5-amp plug standard.

Whereas an NEMA 1-15 plug will fit a 5-15 receptacle, for some peculiar reason the grounding version of the old British Standard 546 plug was designed with the current-carrying pins on a slightly wider spacing than the 2-pin non-grounding version.

The 2-pin, non-grounding plug fits the outlets on the side of the adapter, or into the two middle holes on the front:


The 3-pin, grounding version of the plug fits the bottom holes on the front, with the earth (ground) pin at the very top:


So at any one time this tap can be used for either three non-grounding plugs, or one grounding plug plus two non-grounding types on the sides.

Paul,
I can see that being a solution for those who feel it necessary to bust the ground pin off of nema 5-15 or 5-20 plugs, to make it fit into an ungrounded outlet!
Suprised nothing like that has been thought of here.

-Randy

I have seen older kitchen/bath fans that had the fan motor inside the duct; a short cord & plug went from the motor to a receptacle in the wall of the duct.
Here's the connection: the plugs/receptacles in these fans were of the "y" type that your mystery receptacle would fit (in addition to a "standard" plug).
I believe that what you've found is a replacement receptacle for one of these fans.

Remember- NEMA patterns are not all that old; nor are they mandatory even today. One of my greatest challenges is getting the customer to SHOW ME THE PLUG that is intended to go into the receptacle he want me to install! Then, if the plug is non-NEMA, my next challenge is getting the parts house to put away their NEMA cards!

I have a plug that fits this outlet. It's one of those nasty round ones that are hard to remove from the wall socket. The ground pin is longer than the other two and is marked "ground."


I can post a picture if you want.

I ran into several of these 120V "crow foot" receptacles this summer in the concession area of an old drive-in theatre built in the late 1960s. They originally served popcorn machines, heat lamps, milkshake mixers and cotton candy machines. The new replacement appliances wouldn't plug in.

Welcome to the forum Tim. And yes please, photos of old electrical gear are always welcome here!

These old 120V crowfeet recepts seem to be quite rare. That one in the pic is the only one i've ever come across. I've never seen a crowfoot plug marked for 120V 15A that would fit into that recept... I'm surprised that these were in some place built in the late 60's... I thought they were only used way before that.

 
Comparing MattE’s “universal” boathouse plug to Hutch’s “universal” Siberian plug [in ../Forum9/HTML/000689.html] makes the NEMA 1-15 seem timelessly intergalactic.

[img]http://6L6.net/localuser/bjarn/ecn.matte'scrowfoot.jpg[/img]




[This message has been edited by Bjarney (edited 09-27-2004).]

I have a female crow-foot cord-cap (made by Leviton in the good ole USA, so that should give you an idea of how old it is) that is marked both 120 volts, 15 amps and 240 volts 20 amps.

It fits a standard 10-amp Australian/Chinese plug.

Mine are all Hubbel brand. Thinking, I have one that is somwhere between that one and the 50A type until recently used on range recepticles, I think 20A 250V.