All items-- receptacles, connectors, and caps-- are listed by part # under either voltage rating:
15 Amps. 125 Volts--Polarized
15 Amps. 250 Volts--Polarized
5281 and 5282 are both listed as 125V devices. Whatever the 250V device looked like, it's not shown (presumably like today's 6-15).
Apparently the 20A u-ground devices did not exist until after 1960, and the 30 and 50A devices came in the late '60s.
What I want to know is how many of these were installed. I've never seen one. Three-wire receptacles for grounding were required by the '47 NEC, but the earliest reference I've seen to the 5-15 device is in the '51 NEC Handbook. Even though these were available by '52, how often did the Code actually get enforced? Washers and other appliances didn't start to have grounding plugs until the late '50s, I think. I've been in countless houses from that time period where the washer receptacle is a 1-15 with an ungrounded box.
I did work on a 1950 house last year that had a 15A grounding twist-lock behind the washer. Twist-locks from that era were not the NEMA standard devices we have today. I'm sure that receptacle never got used. The washer was plugged into a cheater, of course.
#153337 - 11/30/0609:53 PMRe: Missing Link? NEMA 5.5-15R spotted
I swear I saw one of these in the laundry room of an old house once... I did a double take and rubbed my eyes when I saw it! If I'm remembering right, I think it looked like a Bryant also.... I kinda wish I'd thought up a reason to get the H.O. to let me replace it now
#153338 - 11/30/0610:35 PMRe: Missing Link? NEMA 5.5-15R spotted
Have seen lots of 5-20's, the typical 20 amp t slot on the neutral, grounded outlet.
I take it there were no electric stoves or dryers until the late 60's?
Looks like you could fit a NEMA 6-15 plug into that receptacle.
I believe some of you have mentioned at one time washers required one of those austrailian looking receptacles?
Lostazhell you have one of them you got from that woman's house in Compton...it's a duplex outlet....top part has the aussie style configuration with ground, bottom is typical dual t slot receptacle with no ground....was that one in the laundry room?
#153341 - 12/18/0610:12 PMRe: Missing Link? NEMA 5.5-15R spotted
I have books from the '20s showing electric ranges, although I've read that they did not become common until GE invented the Calrod element in 1932. The 1936 GE Supply catalog shows the device now known as a NEMA 10-50, including a grounding version with clips that mount on the outside of the cap and make contact with slots in the wallplate. (The 10-50 may be even older than that, for all I know.) The 10-30 configuration was apparently created after WWII for dryers, which did not even exist until 1947 or so.
The exception to the normal rules of equipment grounding, in the case of ranges and dryers (which is expressed for grandfathered pre-1996 installations as 250.140 in the 2002 NEC) was first fully legitimized in 1947. In the 1940 NEC, the practice of grounding a range through the neutral required the special permission of the AHJ. It has been said that wartime shortages of copper persuaded AHJs to grant this permission more freely than in the past, and in 1947 the requirement for special permission was dropped.
Dawg, what I meant is that "U-ground" devices only existed in the 5-15 and 6-15 configurations in the '50s. The 5-20 devices were here by '64 at least, and the 30A and 50A U-ground devices came later.
I don't know what year the NEMA 14 devices were created, but Article 550 (mobile homes) did not enter the Code until 1965. Presumably the adoption of this article created a need for a three-pole four-wire device with a separate ground. I'm sure most stateside ECN members know this already, but the requirement to use NEMA 14 devices in buildings other than mobile homes is only ten years old.
(Again, the fact that the NEC did not mention mobile homes until 1965 in no way means that they didn't exist before that time. They just weren't regulated. The entire mobile home industry, one might argue, is another legacy of WWII.)
[This message has been edited by yaktx (edited 12-22-2006).]