The 1947 NEC Handbook mentions a requirement for at least one receptacle in the laundry area to be a three-wire type, with the third wire reserved for equipment grounding. There is no elaboration on the type of receptacle required.
The 1951 Handbook has the same requirement, but has an illustration of a duplex receptacle and plug of the configuration that we now know as NEMA 5-15. I believe it can be safely assumed that this configuration (now standard throughout North America) dates to 1950 or 1951.
I recently did some work on a 1950 house which had a porcelain Hubbell twist-lock receptacle in the laundry room. I am sure this was installed to meet the 1947 Code requirement. I am 99.9% sure it has never been used!
American sparkies who are familiar with the NEMA straight-blade chart frequently mistake the NEMA 10-20 for the Aussie/NZ configuration, but this is incorrect. The pix Paul posted on this thread are of a different USA standard, one dropped before the NEMA chart was created. Like most T-slots, it is rated 125V 15A/ 250V 10A (probably the origin of the Aussie 10A standard), whereas the 10-20 has wider-spaced pins and is rated 250V 20A.
I still see 10-20 receptacles on occasion. Here in Texas, they were used for window air conditioners in the '50s. If the house was upgraded to central A/C, the window unit receptacle was no longer needed, and therefore was never upgraded to later standards.
BTW,
Woodhead still makes a line of devices in the 10/15A non-NEMA configuration that more or less matches the Aussie/NZ standard.
[This message has been edited by yaktx (edited 01-04-2006).]
[This message has been edited by yaktx (edited 01-04-2006).]
