Nema plug questions.

A couple of questions about the design of NEMA plugs:
What is the purpose of the small holes near the tips of the hot and
neutral blades in most, but not all, of the smaller straight blade plugs, e.g. 1-15, 5-15, 6-15, 7-15, 5-20, 6-20 etc? There's nothing in the receptacle which locates in them, and they reduce both the cross-sectional area and the surface contact area at just the point where the blades make contact with the receptacle. They don't seem to serve any useful purpose, and some plugs don't have them. Are they there for some historical reason? Wouldn't eliminating them provide better contact?
The ground pin on moulded-on 5-15 plugs is usually a thin metal tube, with the end domed over to form a test tube type shape. On re- wireable plugs, and on the larger ones, it's usually made from a flat strip of brass bent into a 'U' shape. Why the difference? Wouldn't a better contact be made if they wee all the same shape, rather than the contacts in the receptacle having to work with both shapes? Come to that, why not use a simple solid round or rectangular bar, as most other plugs in the world, except side contact types such as BS 196-1961 and German Schuko ones do?
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On Dec 22, 6:15 am, snipped-for-privacy@mail.croydon.ac.uk wrote:

I cannot tell you why they were used in the first place but they allow the installation of lock out tag out blocks on the ends of cords when servicing larger machines. -- Tom Horne
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On 23/12/10 19:57, in article snipped-for-privacy@c2g2000yqc.googlegroups.com, "Tom

Thank you to those who posted answers to my questions. I now have another one. On Ebay at the moment there is a strange receptacle. Both hot and neutral holes are 'T' shaped, like the neutral on 20 A ones; there is no ground, but the hot and neutral are shifted up to the position where they would have to be if there was one. What is the purpose of this thing? It's described as being for replacement purposes only, so presumably it's obsolete. It would seem to be able to take either a 1-15 120V or 2-15 240V plug, but why would you want such a thing? Surely you'd want to avoid plugging something into the wrong Voltage.
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My house still has a couple of such outlets, but the slots are centered. I never knew of the reason for the "T" slots. I've never seen anything with a 2-15 plug w/o a ground pin.
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?
"Michael Moroney" wrote in message writes:

My house still has a couple of such outlets, but the slots are centered. I never knew of the reason for the "T" slots. I've never seen anything with a 2-15 plug w/o a ground pin.
-------------------------------- I have seen these for "razor" outlets which can tale a horizontal (240V or parallel 120 V) plugs. They were 240V (in New Zealand) but took my camera battery charger without an adapter.
I have no idea of the rating but I expect that they could handle a dual voltage hair dryer (1KW?)
While these are not shown, the following is a good reference for travellers.
http://www.kropla.com/electric2.htm
Don Kelly cross out to reply
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On 4/1/11 02:18, in article TrvUo.37537$ snipped-for-privacy@newsfe01.iad, "Don Kelly"

At least here in the UK that would not be the case. These are the only type of outlets which are allowed to be installed in bathrooms, and if so installed they must contain an isolating transformer. Since it is a simple matter to tap the secondary winding of this transformer these shaver sockets are almost always dual-Voltage. They usually take Nema 1-15, Australian angled blades, two-pin 'Europlugs' which fit most European sockets except the UK but fit most of them badly, and British shaver plugs. I think they may also take the long obsolete British 5 2-pin plug, but I'm not sure.
I don't know the rating of the transformer, but it's certainly far less than 1 kW. They are only supposed to be used for shavers and electric toothbrushes. Adapters to fit shaver plugs into BS 1363/A 13 A socket must be fitted with a 1 A fuse, which is physically smaller than fuses of higher rating.
If you were wondering how we use hairdriers in bathrooms, we don't.
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Op 30-1-2011 14:12, Stephen Furley schreef:

Here in austria the transformer says 20 VA.
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Michael Moroney Inscribed thus:

WAG ! Adaptor socket for flat blade plugs. Take either horizontal or vertical flat blades. Maybe !
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Did they once use plugs with two horizontal blades for 120V (110V at the time) ? I've never seen any.
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Michael Moroney Inscribed thus:

I've only seen the ones with vertical blades for power usage ! I've seen similar sockets in bathrooms that will take several types of plug, usually for things like electric shavers. The plugs I've seen with horizontal blades have been for telephones, mainly in Eastern Europe.
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On 2/1/11 22:16, in article ifqtco$prg$ snipped-for-privacy@news.eternal-september.org, "Baron"

The shaver sockets are made to take various plugs, round pins for most of Europe, shorter fatter round ones for the UK, parallel flat ones for the USA and angled flat ones for Australia.
For normal mains sockets in the USA vertical blades are 120V, horizontal ones are for 208 or 240V. That's for 15A; for 20A the hot blade is as for 15A and the neutral one is rotated 90 degrees. 20A sockets have a 'T' shaped slot for the neutral blade, so they can accept both 15A and 20A plugs, but I've never seen one with two 'T' slots like the one I was asking about. Angled blades are 277V (phase Voltage on a 480V three phase supply), and in theory one horizontal and one angled is for 347V (phase Voltage on 600V supply), but I've never seen one of these.
Those are the only ones that I can remember; if I need to know 30, 50 or 60 A ones, or three phase ones etc. then I have to look them up.
http://parkwaymarina.com/nemachart.htm
That's just the straight blade ones; there are rather more of the locking type. Thank goodness I'm in the UK; things are much simpler here.
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Stephen Furley wrote:

What is the item number on Ebay?
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For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!
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On 2/1/11 19:51, in article gLKdnYYnzKvcSr3QnZ2dnUVZ snipped-for-privacy@earthlink.com,

230566259249
The box shows it as being 125 V 15 A, so I can't see what the horizontal parts of the slots are for.
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That looks fairly modern, unlike mine which appear to be ceramic.
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Stephen Furley wrote:

The outlet is marked, Made in Mexico. I don't see any UL markings on it. Nema 15R is a two wire polarized receptacle. I'm not sure that was made for the US market.
--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!
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Leviton devices have been made in Mexico for many years now. The description explicitly states it is not UL listed.
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On 3/1/11 02:26, in article ifrc4k$qin$ snipped-for-privacy@pcls6.std.com, "Michael Moroney"

As far as their receptacles are concerned, the older ones seem to be made in the USA and the newer ones in Mexico, which suggests that this strange one is not that old. Their lampholders, the main product of theirs that I use, seem to be made in China.
I collect lamps and lighting equipment and have quite a lot of American HID lamps of various types. Many of them are quite different to the ones we have here in Europe, which is why I need strange (for this country) things like E39 and position oriented lampholders, and why I am probably one of the few people in England to have 1 kVA worth of 277 V 60 Hz. power available at home.
What exactly is the significance of the UL marking? Do things have to be so marked to be used in the USA?
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AFAIK
Underwriters Laboratory approval markings were required to be used in the USA. In Canada it was CSA (Canada Standards Association), only. Now the UL comes with several smaller letters beside it to clarify which country it is approved in. cUL or ULus or cULus (both). Also the governments have both decided to accept reciprocal companies marks for approvals, so that the USA accepts standards from CSA also.
Note UL and CSA are private companies and not affiliated with either government.
As far as their receptacles are concerned, the older ones seem to be made in the USA and the newer ones in Mexico, which suggests that this strange one is not that old. Their lampholders, the main product of theirs that I use, seem to be made in China.
I collect lamps and lighting equipment and have quite a lot of American HID lamps of various types. Many of them are quite different to the ones we have here in Europe, which is why I need strange (for this country) things like E39 and position oriented lampholders, and why I am probably one of the few people in England to have 1 kVA worth of 277 V 60 Hz. power available at home.
What exactly is the significance of the UL marking? Do things have to be so marked to be used in the USA?
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On Mon, 3 Jan 2011 13:32:31 -0500, "Josepi, the Clueless Moron"

Utter nonsense. UL is a private organization. They have no special powers under US law.

As such, at least in the US, they have no spacial legal standing. There are other listing agencies, though isting isn't even al requirement under US law.
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Holy smokes. I cleaned out my bozobin and noted two things immediately 1) you still can't read. 2) you are still a moronic troll
<PLONK>
wrote:>AFAIK

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