ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades History of the Australian plug

I quote from Sec. 1991 of the 1951 NEC Handbook, comments:


I assume the earlier crowfoot receptacles (like today's NEMA 10 devices) did not have the "ground" contact bonded to the yoke.

The comment continues:


The editor, Arthur Abbott, and his successor, Frank Stetka, were still waiting as of 1959 for this UL change to take place. I don't know when it finally happened, as my '62 and '65 books are not Handbooks. It was a non-issue by '68 (and of course forgotten today).

[This message has been edited by yaktx (edited 01-05-2006).]

[This message has been edited by yaktx (edited 01-05-2006).]

Isn't that what we call the "contour plug" in here?


So what about appliances with those contour plugs? I guess they're not sold like that over there?

I'm assuming these were the precursor to the T-slot... I've found these oddities in turn of the century houses and buildings... this one shows a sole rating of 10A 250V




Then there's the T-Slot/Aussie combo I found in a 1920's liquor store.. Made by Hubbell




On the back it doesn't mention anything about grounding like the combo unit PaulUK posted above... It just shows "2 wire terminals" and "3 wire terminals"

Randy,

Is there continuity between the vertical pole of the crowfoot and the mounting strap?

I've never seen one of these referred to as a "grounding" receptacle in old catalogs and textbooks. They are always described as "3-wire polarized", but they seem to have been used the way we use a NEMA 5-15 today. How was this one wired when you took it out?

About 90% of housing stock in my area is postwar, so I don't see as much of this kind of stuff. I have been hunting for a receptacle like the one in the first photo, which does look functionally equivalent to a T-slot. (The parallel slots don't appear to be polarized.)

The crowfoot shown does appear to have about the same blade spacing as the 1-15, and we already know that a 1-15 plug can be mangled to fit an Aussie receptacle, so this must be the parent pattern. (Of course, this may be a later iteration.)

Interesting that we had this pattern way back in the '20s, and we could have gone with it and had grounding receptacles from the beginning, as Australia and New Zealand have. But no, we had to wait 40 more years, and now, forty years after that, there are still millions of buildings out there with ungrounded receptacles. Oh well, more work for us, right?

Oh, Randy, another thing:

How do you manage to find 70+ year-old devices that aren't covered in 50 coats of paint?

yaktx,
Regarding the crows foot outlet, there's no continuity to the mounting yoke from the vertical pole, The way the outlet was wired was a little different, and I'm not sure if it was acceptable at the time or not... The T-slot outlet was wired typical, but the crowfoot outlet was wired 240V between the angled blades and the neutral from the T-slot looped up and over to the vertical blade of the crowfoot... I took it out and replaced it with a Nema 5-20 duplex and split it for 2 dedicated ckts.

The outlet in the first pic is from a house built in 1900 in Compton, CA.. It's the only duplex of it's style I've ever seen (So of course I had to recommend it be replaced )There isn't any polarity to it, although it's worn to the point that a polarized plug will insert into it. I have a few of the single style ones from the same house and a couple others built in 1898 and 1903 (I got some snazzy pushbutton switches from those houses also )
Just for the sake of it, I tweaked an old 2 prong plug with a pair of needle nose a little bit and it fit into the crowfoot plug just as if it was made for it, showing the blade spacing is close, if not exactly the same.

It is interesting to think of having grounded outlets waaaaay back in the day, but compared with our modern NEMA 5-15, 5-20, etc... there is one thing of signifigance, and thats the fact of the ground pin being longer than the current carrying blades... Ensuring that the plug has grounding contact made before making energized contact.. (Now if we could make some foolproof way of keeping 5-15's from being installed without a ground wire )
Yeah, we still have millions of homes lit with knob and tube, and other ungrounded systems.. "More work for us..." Job security

Randy

PS... the outlet on the top didhave 50 coats of paint on it... 2 words, "Goof Off"

Folks,
Not looking to detract from the very good Original post by Aussie, but this was mentioned in a recent Break-In magazine (Amateur Radio magazine).
I will type it out verbatim so that there is no confusion if I try and "edit" it.

That comment came from Gary Henderson, ZL2TNH.

Hmm, longer pins, I would never have thought about that.

{Sorry about the thread-jack Aussie}

{Message edited for a couple of typo's



[This message has been edited by Trumpy (edited 01-06-2006).]

Many thanks for that excellent explanation.

This is another of those issues where things start to make sense once you get the history behind it (and I'm a firm believer that in many technical fields we should be teaching newcomers not just current standards but also enough of the historical development to give them an understanding of how we got to where we are today).

It's easy to look at these varying connector configurations today and say we could have come up with a more standardized system, but the T-slot recepts. would have been a quite logical arrangement to adopt at a time when both parallel and tandem-blade plugs were in use for the same voltage.

Re: Aussie vs. Chinese plugs:

While I can come up with several reasons for avoiding Chinese stuff altogether, I can't help feeling that this is over-reacting somewhat. Is one whole extra millimeter on the length of the pins really going to turn a safe connector into a shock hazard?

I think it's over-reacting, but then again...the pins on our plugs sometimes vary in length by a millimeter or two.

Some are slightly shorter and some are slightly longer.

All depends on the provenance of the plug and also I guess how much rubber is deposited around the pins (in the case of a molded plug).

Some replacement plugs usually have slightly longer (and thicker) pins. They help stay in the socket better.

A millimeter? Considering that there is quite a variance in the actual molded rubber or plastic design with different cordset and different cord cap manufacturers, I can't see an extra millimeter on the blades being more of a shock hazard than a slimmer designed plug....

Besides, aren't most people smart enough to kinda get the idea you aren't supposed to touch the shiny metal things as they disappear into the wall outlet? (ok.... I might be stretching that )