T-slot plugs and 20 amp appliances?

|
| |> <SNIP> |>> |>> The legacy T-slot outlet was an ungrounded outlet that had the T-slot
|>> hole |>> for both conductors. I still occaisionally see them around on very old |>> wiring. The intent was to be a single product usable for either 120V or |>> 240V circuits. You can see the risks it exposed. It would not be |>> allowed |>> today, and may not have ever been technically allowed. |> |> I think I just replaced on of these. Are you saying that it was desighned |> to be wired ether to a 120v curcuit (using the standard vertical " | | " |> plug) or a 240v curcuit (using a "- -" plug)? |> |> Is a "- -" plug standard for 240v? if so what amprage? |> |> Just curious (mine was definatly a 120v 15a curcuit |> | | | | There is a 120v/20A plug that looks like | -- , this is what they are | talking about. The standard 120V/15A plug has | |, and the 20A version has | | -- (or -- | ) configuration.
If the plug does NOT have a ground pin, then "| -" and "- |" are just the same thing turned 180 degrees. It represents 240V 20A ungrounded. It has a designation NEMA 2-20. A NEMA 2-20P plug will mate with a NEMA 6-20R outlet. It will also mate with a NEMA 5-20R which can be a problem for an appliance that could be a hazard operating on a lower voltage. There is a NEMA 1-20 for 120V 20A ungrounded. It has a vertical blade/slot and one with a short angle on it. It will mate with a NEMA 5-15R/5-20R combination, but not with a NEMA 5-20R-only that is designed to not accept NEMA 5-15P (and not with any 240V outlet configuration).
A more interesting receptacle configuration is the NEMA 14-15R. It accepts both a NEMA 14-15P as well as a NEMA 6-15P. The NEMA 14-15R is a NEMA 6-15R with an added "-" blade above (for ground pin down) the other "- -" blades to add the neutral conductor. I have not seen this manufactured anywhere.
You can see a NEMA 14-15R example in these illustrations for simplex and duplex configurations:
http://phil.ipal.org/usenet/aee/2008-05-29/fourfaces.html http://phil.ipal.org/usenet/aee/2008-05-29/twelvefaces.html
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snipped-for-privacy@ipal.net writes:

Interesting. I never knew that existed. I have a duplex recepticle that has a 5-15R on the top and a 6-15R on the bottom. Since the neutral has to be there anyway, they could have added the extra pin easily to the bottom outlet. But as you mention the 14-15R is either rare or nonexistent. (my duplex outlet itself is oddball)
BTW a "face" you don't have is a 347V 15A outlet. It has one horizontal "eye" and one slanted "eye" like the 7-15R. I wonder if it (and the 277V 15A 7-15R outlet) are also merely theoretical or are there devices that actually use them.
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On Fri, 30 May 2008 13:00:36 +0000 (UTC) Michael Moroney
| snipped-for-privacy@ipal.net writes: | |>A more interesting receptacle configuration is the NEMA 14-15R. It accepts |>both a NEMA 14-15P as well as a NEMA 6-15P. The NEMA 14-15R is a NEMA 6-15R |>with an added "-" blade above (for ground pin down) the other "- -" blades |>to add the neutral conductor. I have not seen this manufactured anywhere. | | Interesting. I never knew that existed. I have a duplex recepticle that | has a 5-15R on the top and a 6-15R on the bottom. Since the neutral has | to be there anyway, they could have added the extra pin easily to the | bottom outlet. But as you mention the 14-15R is either rare or | nonexistent. (my duplex outlet itself is oddball)
That duplex is still manufactured by at least Hubbell and Leviton.
| BTW a "face" you don't have is a 347V 15A outlet. It has one horizontal | "eye" and one slanted "eye" like the 7-15R. I wonder if it (and the | 277V 15A 7-15R outlet) are also merely theoretical or are there devices | that actually use them.
That would be a NEMA 24-15R. The 24-20R is a mirror image of it. I have seen the 7-15R duplex in the Leviton catalog.
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Michael Moroney wrote:

I've got one of those; I've also seen a 20A version, with a 5-20R and a 6-20R.

I have seen a 7-15R, but I cannot remember where. I've never seen the 347V version, but then I don't think I've ever seen a 347/600V installation.
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snipped-for-privacy@ipal.net writes:

I still have a couple of these, and for a long time I wondered about the intent of the T slot. House was built in 1940.
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On Fri, 30 May 2008 12:39:37 +0000 (UTC) Michael Moroney
| snipped-for-privacy@ipal.net writes: | |>The legacy T-slot outlet was an ungrounded outlet that had the T-slot hole |>for both conductors. I still occaisionally see them around on very old |>wiring. The intent was to be a single product usable for either 120V or |>240V circuits. You can see the risks it exposed. It would not be allowed |>today, and may not have ever been technically allowed. | | I still have a couple of these, and for a long time I wondered about the | intent of the T slot. House was built in 1940.
I'm guess they are installed in place. If you ever decide to replace them in the wall, keep the original devices. They could be valuable antiques.
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snipped-for-privacy@ipal.net writes:

FWIW,I just saw an old (1946) Sylvester/Tweety Bird cartoon and it showed one of these T slot duplex outlets. What was odd was the outlet faces were rotated 90 degrees, which I've never seen in a real outlet.
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On Wed, 4 Jun 2008 15:52:24 +0000 (UTC) Michael Moroney
| snipped-for-privacy@ipal.net writes: | |>The legacy T-slot outlet was an ungrounded outlet that had the T-slot hole |>for both conductors. I still occaisionally see them around on very old |>wiring. The intent was to be a single product usable for either 120V or |>240V circuits. You can see the risks it exposed. It would not be allowed |>today, and may not have ever been technically allowed. | | FWIW,I just saw an old (1946) Sylvester/Tweety Bird cartoon and it showed | one of these T slot duplex outlets. What was odd was the outlet faces | were rotated 90 degrees, which I've never seen in a real outlet.
I don't follow what kind of rotation this was. There are some possibilities that I can imagine:
1. The whole duplex was rotated, making each of the two outlets left and right of each other. The ends of the T's are up and down.
2. Each of the 2 outlets was independently rotated, while remaining one above the others. The ends of the T's are up and down.
3. Just the T's themselves are rotated. That would look weird.
4. A combination of rotating the duplex and rotating the outlets. This would have left and right outlets, but leaving the ends of the T's sideways as they were before.
See also:
http://phil.ipal.org/usenet/aee/2008-06-04/want.html
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snipped-for-privacy@ipal.net wrote:

In an old book on wiring I saw a picture of a duplex outlet used for DC - it also had a T-slot but had the t and straight slot arranged vertically. No ground pin, of course. I've never seen anything that described standards for DC wiring - I suspect any books on that would be before WWII at least.
Bill ( Just when did Toronto have DC distribution, any way? I know DC hung on in a small way in New York until just a few months ago - but I was never aware there was much DC central station power in Canada. )
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| In an old book on wiring I saw a picture of a duplex outlet used for DC | - it also had a T-slot but had the t and straight slot arranged | vertically. No ground pin, of course. I've never seen anything that | described standards for DC wiring - I suspect any books on that would be | before WWII at least.
And a book that old would very likely be unrelated to today's standards on safety.
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snipped-for-privacy@ipal.net writes:

I'm not sure I understand what #3 is, but what I meant is #2. The outlets are one above the other the way most are currently, but a normal flat blade (120V) plug would go in with the blades horizontal, one above the other.
Like this:
| ---
--- |
| ---
--- |
I think I saw another outlet like this in another cartoon but mounted horizontally, thus like #4. It was a while ago that I saw that.
Another odd one we had when I was a kid. A combination outlet/faceplate that had 5 two blade outlets in a normal duplex box size. Yes they all (barely) fit! You could only plug the smaller lamp cord plugs in if you wanted to use them all. I wish I kept it when the neighbors renovated the place (we moved next door). This just had the vertical slots, no T slots. Obviously no ground pins (no room!).
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Michael Moroney wrote:

I took out one that had 3 in one. I had never seen that before. No grounds of course. Eric
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|> Another odd one we had when I was a kid. A combination outlet/faceplate |> that had 5 two blade outlets in a normal duplex box size. Yes they all |> (barely) fit! You could only plug the smaller lamp cord plugs in if |> you wanted to use them all. I wish I kept it when the neighbors |> renovated the place (we moved next door). This just had the vertical |> slots, no T slots. Obviously no ground pins (no room!). | I took out one that had 3 in one. I had never seen that before. No | grounds of course.
Something like this?
http://static.zoovy.com/img/kyledesign/-/light_switchplates/whitedespardswitchesoutlets
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snipped-for-privacy@ipal.net wrote:

http://static.zoovy.com/img/kyledesign/-/light_switchplates/whitedespardswitchesoutlets
Yeah the cover plate was like that. Hell, I once had an outlet strip that had no slots at all, just 2 continuous grooves. Seemed sort of dangerous.. Eric
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Eric wrote:

They were, when they got old. They didn't hold the plugs tight, and overheated, like any other worn outlet. That crap was common on benches in TV & radio repair shops in the '60s & '70s.
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On Thu, 5 Jun 2008 02:04:31 +0000 (UTC) Michael Moroney
| snipped-for-privacy@ipal.net writes: | |>On Wed, 4 Jun 2008 15:52:24 +0000 (UTC) Michael Moroney
| |>| FWIW,I just saw an old (1946) Sylvester/Tweety Bird cartoon and it showed |>| one of these T slot duplex outlets. What was odd was the outlet faces |>| were rotated 90 degrees, which I've never seen in a real outlet. | |>I don't follow what kind of rotation this was. There are some possibilities |>that I can imagine: | |>1. The whole duplex was rotated, making each of the two outlets left and right |> of each other. The ends of the T's are up and down. | |>2. Each of the 2 outlets was independently rotated, while remaining one above |> the others. The ends of the T's are up and down. | |>3. Just the T's themselves are rotated. That would look weird. | |>4. A combination of rotating the duplex and rotating the outlets. This would |> have left and right outlets, but leaving the ends of the T's sideways as |> they were before. | | I'm not sure I understand what #3 is, but what I meant is #2. The | outlets are one above the other the way most are currently, but a normal | flat blade (120V) plug would go in with the blades horizontal, one above | the other. | | Like this: | | | | --- | | --- | | | | | | | --- | | --- | |
I do recall seeing an outlet oriented like that, but it was a single not a duplex. But a duplex would be entirely plausible as increased use of this new-fangled electricity took place.
| I think I saw another outlet like this in another cartoon but mounted | horizontally, thus like #4. It was a while ago that I saw that.
Mounting outlets horizontally, so one is left or right of the other, is common in Europe. I see advantages to it and would like to do that for my home. But I still want the ground pin on the up side, not left or right.
| Another odd one we had when I was a kid. A combination outlet/faceplate | that had 5 two blade outlets in a normal duplex box size. Yes they all | (barely) fit! You could only plug the smaller lamp cord plugs in if | you wanted to use them all. I wish I kept it when the neighbors | renovated the place (we moved next door). This just had the vertical | slots, no T slots. Obviously no ground pins (no room!).
I remember seeing something somewhat like that once. It had 2 very LONG slots and you could squeeze in more plugs if they were thin. No ground.
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On 5 Jun 2008 14:38:29 GMT, snipped-for-privacy@ipal.net wrote:

These are the same people who brought you the Acme rocket powered roller skates.
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snipped-for-privacy@world.std.spaamtrap.com (Michael Moroney) writes:

I happened to see a real but newer outlet like that (actually about 4 of them), older GFI outlets with one outlet above the others, but rotated so that the ground pins were on the left. The test buttons were between the outlets like other GFI outlets.
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| If you have a 20A circuit that has multiple outlets, you do not need the | T-slot recepticle. | | You need a t-slot recepticle when you install a dedicated 20A circuit. The | T-slot is a visual queue that the power in the wall will operate a 20A | device. If you actually have a 20A device, it must have a t-slot plug to fit | the recepticle.
Note that the above is equally correct for both 120V and 240V configurations.
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