Talk:NEMA connector

Upside down 5-15

I'd question the rationale in the paragraph:

"It is customary in the U.S. to install 5-15 and 5-20 receptacles with the ground pin down. This is to ensure that a loose cord remains grounded even if its two prongs no longer contact the line voltage. As a safety measure, however, many receptacles are now installed "upside down" (with the ground pin up.) In the case of a metal object falling onto a dislodged cord, the foreign object is less likely to straddle two conductors, possibly avoiding a short circuit."

As I understand the practice, the goal is to make it less likely that a metal object falling between the plug and socket will touch the live blade without first touching the ground pin. A short circuit, which would trip the circuit breaker, is a more desirable outcome than a live bare metal object that someone might come in contact with. --agr 11:28, 14 June 2006 (UTC)[reply]

In every diagram of NEMA connectors I've seen, the ground pin is on the top. The NEMA standard document (available in PDF format here: http://www.nema.org/stds/wd6.cfm) shows the ground pin on top. Leviton has a nice diagram of all the pin configurations showing ground pins on top here: http://www.leviton.com/sections/techsupp/nema.htm

I agree that the reason for having the ground pin on top is to prevent conductive objects dropped between the plug and receptacle from contacting a live pin. The loose cord explanation for having the ground pin on the bottom doesn't entirely make sense, since the ground pin's primary purpose is to ground any internal shorts and trip the circuit breaker. With the plug loose enough so the live pins no longer contact, there will be no reason to protect against internal shorts, since there will be no internal voltage. The ground pin is longer so it is the first pin to contact, so any internal shorts will go directly to ground upon insertion. I believe, in all seriousness, that the reason it is customary in the U.S. to install these receptacles with the ground pin down is because people like to see the "smiley face". I don't know if the NEC specifies one way or the other. --Rich 02:35, 20 July 2006 (UTC)[reply]

I think a part of the reason the connectors are installed "ground pin down" is the mnemonic attraction: the earthed safety conductor faces the earth. I also wonder if there was a hang-over effect from the earlier ungrounded recepticles. That is, was it conventional to install these with neutral leftwards and hot rightwards? That would certainly explain keeping that convention when 5-15 connectors came around.

Atlant 11:35, 20 July 2006 (UTC)[reply]

If there is a reason for installing them ground down, I think it must be anthropomorphic. They look like faces. I'll admit that's why I prefer to install them that way. Rich is correct that the NEC does not specify.Yak99 00:10, 23 April 2007 (UTC)yak99[reply]

6-20

"The 20 A plug has the neutral pin rotated 90 degrees, and the 6-20R receptacle may have a T-shaped hot hole, to accept both 6-15P and 6-20P plugs"

i didn't think american 240V wiring had a neutral so both holes are hot. Plugwash 02:13, 24 June 2006 (UTC)[reply]

Nearly all wiring has a neutral, without neutral, there is nothing reliable to refrence the 240 volts to. 48v 03:40, 11 July 2006 (UTC)[reply]

Ok i could have phrased that better, in US wiring 240V basically means both hots so in a socket that supplies only 240V (e.g. the nema 6 series we are discussing here) there won't be a neutral. Plugwash 20:43, 11 July 2006 (UTC)[reply]

So I presume that by 'both hots' you mean that there are two seperate 110 volt legs which makes plenty of sense. My question is this: what are the 110v legs refrenced to if there is not neutral?

There is a neutral in the supply system just not at the socket, relative to neutral the two hots are the same magnitude but 180 degrees out of phase with each other, so equipment that needs 120V is connected between one hot and neutral (and uses a 1- or 5- series plug), equipment that needs 240V is connected between both hots and not connected to the neutral (and uses a 2- or 6- series plug) equipment that needs both (e.g. cookers, clothes driers etc) is connected to both the hots and the neutral (and uses a 10- or 14 series plug). Plugwash 23:24, 11 July 2006 (UTC)[reply]

Ahh. That makes much more sense. Thanks for explaining! 48v 23:45, 11 July 2006 (UTC)[reply]

Separate?

Many of these sections could be expanded into their own articles including common useages, regions, histories etc. Should we consider seperating this article into many smaller articles which would be easier to expand? 48v 03:40, 11 July 2006 (UTC)[reply]

The article isn't really big enough to need it yet but when it becomes so just split out long sections and replace them with a shorter summary and a main article link. Plugwash 21:05, 11 July 2006 (UTC)[reply]

Long winded

My word, this article does babble on. One picture would truly be worth 1000 words - we could then condense the text to "NEMA connectors use different combinations of pin widths, orientation, and dimensions to furnish connectors that are unique to a particular voltage, current capacity, and grounding system" or words to that effect. Put on my to-do list, I'm sure I can redraw from CEC and NEMA to save a ton of space here. --Wtshymanski 17:46, 21 July 2006 (UTC)[reply]

Hear, hear! [But I can't help noticing that it's been nine months since you wrote that. What's keepin' ya? :-) ] 24.6.66.193 19:23, 18 April 2007 (UTC)[reply]

Busted. But I've been fighting off the kibibytes and remodelling a bathroom...it's been a busy year. --Wtshymanski 21:46, 18 April 2007 (UTC)[reply]

Just remember: Black goes to black, white to white, and always use GFCIs ;-).

Atlant 12:12, 19 April 2007 (UTC)[reply]

nema 2 series dangerous.

it was claimed in domestic ac power plugs and sockets in content now moved to unusual and obsolete plugs and sockets that the 2- series connectors were dangerous. I can't see any danger in using them with 240V class 2 equipment other than the slight risk of connecting a 240V appliance to 120V (which would most likely just result in the appliance not working) would anyone like to comment on this? Plugwash 17:20, 15 September 2006 (UTC)[reply]

Are 5-15 connectors allowed on 20A circuits in the USA

if they are why do people bother with the 5-20 T slot in kitchens?

if they are not why is the 5-20 T slot (which also allows a normal domestic plug to be connected to a 20A circuit) allowed? Plugwash 11:51, 15 September 2006 (UTC)[reply]

Yes, 5-15 receptacles are allowed on 20 amp circuits. For example, most North American GFCI outlets use 5-15 pinning but are rated at "20A pass-through".

I'm not sure I understand the second half of your question, but I'll make some observations: You'd certainly want kitchen convenience outlets to accommodate 5-15 plugs because most of the loads in the North American world have that connector, even pretty hefty electric cooking loads like table-top broilers and big coffee makers. On the other hand, accommodating a 5-20 plug is a nice feature and cues the user that the circuit is a 20A circuit, even if there are very few domestic loads with a 5-20 plug. (I've only seen 5-20 plugs in industrial environments.) If I were to rewire my kitchen again, I'd probably install 5-20R T-slots for that reason.

Atlant 13:45, 15 September 2006 (UTC)[reply]

5-15 receptacles are allowed on 20A circuits as long as there is more than one receptacle on the circuit. In some jurisdictions, a 5-15 duplex counts as more than one receptacle, in others, not. Where I live, if you have just one receptacle on a circuit, it has to be a "single" receptacle, and it has to be a 5-20R. A 5-20R on a 15A circuit is not allowed anywhere.Yak99 00:14, 23 April 2007 (UTC)yak99[reply]

why do air conditioners get special treatment?

are they in some way more dangerous than other large portable loads (such as portable heaters) or is it just a case of them gaining more attention because there are in more common use. —The preceding unsigned comment was added by Plugwash (talk • contribs) .

Probably because they're inherently wet during operation (from condensate) and often wet from precipitation.

Atlant 23:04, 15 September 2006 (UTC)[reply]

Weird image...

Is there a reason the GFCI pic is a line drawing? I thought we only used them for sex acts? 68.39.174.238 20:21, 10 October 2006 (UTC)[reply]

Feel free to replace it with a photo provided the photo shows all the relavent features reasonablly well. Plugwash 20:00, 11 October 2006 (UTC)[reply]

links to diagrams

Given that the NEMA standard is available for free download, are the other links necessary? (Argument for: the NEMA link isn't a direct link; it requires that you agree with a simple license.)

Jordan Brown 08:13, 26 February 2007 (UTC)[reply]

Furthermore, it's a very large file that contains painstakingly intricate blueprint-style drawings intended for product designers. Simple, straightforward diagrams aimed at ordinary people would be preferable, such as the ones found here:

http://www.frentzandsons.com/Hardware%20References/twistlockplugandreceptacle.htm

http://www.frentzandsons.com/Hardware%20References/plugandreceptacleconfiguratio.htm

24.6.66.193 05:01, 21 April 2007 (UTC)[reply]

like, NEMA10, eh???

"In Canada, the use of NEMA 10 devices was discontinued much earlier (if it was ever permitted at all), so NEMA 14 devices are more common there."

Um, so were they ever permitted? or were they not? It's got to be one or the other, eh? --carlb 05:24, 6 March 2007 (UTC)[reply]

terminology

Perhaps a brief discussion about the meaning of words like "plug" "socket" "receptacle" "connector" etc. It seems different words are being used to describe similar things, and the same word used to describe different things. So, first off, these words need to be defined, and a standard usage needs to be adopted so as to not be so confusing. 143.127.3.10 21:08, 5 June 2007 (UTC)[reply]