Strange Plug and Receptacle

[mbrooke]

Can anyone tell me anything about this plug or the accompanying socket? It looks like it was semi popular at one point being use on equipment, in buildings as a standard receptacle and even listed in several old electrical books going as far into 70s. No in-depth description however.

Also interesting in that this combination is listed as being polarized but apparently there is a duplex version which swaps live and neutral. Equipment drawings also seem to display an indifference to polarity relative to each other. ie two competing standards as to which side is hot and which was supposed to be neutral.

https://imgur.com/jzgwlVi

https://imgur.com/xwzaaTc

https://imgur.com/76KEy1A

 

[mbrooke]

Polarity swap:

https://imgur.com/a/6Gp9Eju

 

[mbrooke]

From an ANSI symbols book:

https://imgur.com/a/TM08MjF

110 volts indication:

https://imgur.com/a/BYH02ot

 

[ramsy]

Lookup NEMA 10-20, and NEMA 10-50

 

[LarryFine]

 

[SSDriver]

They used to be pretty standard on large wall/window air conditioners. When used with 240v they often did't have an EGC. You can still buy them, McMaster has them in stock.

 

[mbrooke]

Lookup NEMA 10-20, and NEMA 10-50

Don't think its a NEMA 10-20, to small. But it sure is interesting that a NEMA 10-15 doesn't exist.

 

[mbrooke]

View attachment 2554039

Why is there no 10-15P?

 

[retirede]

It looks like the standard configuration used in Australia, it it’s been 10 years since I’ve been there, so not sure.

 

[ramsy]

Why is there no 10-15P?

Same reason legacy NEMA 10–30 outlets for 3-wire 230v Electric dryers are replaced by NEMA 14-30 outlets. NEMA 10 series is missing the grounding prong when neutral is used for control circuits.

 

[jeff48356]

They used to be pretty standard on large wall/window air conditioners. When used with 240v they often did't have an EGC. You can still buy them, McMaster has them in stock.

Yes, I believe that used to be called a "crow foot" receptacle. Most commonly used for 240V air conditioners in the 70's.

 

[norcal]

That obsolete configuration is what the current plug/receptacles used in Australia, & New Zealand are based on, the domestic ones used to be rated 20A 250V, they were changed to the current rating of 20A 125/250V.

 

[Frank DuVal]

Yes, I believe that used to be called a "crow foot" receptacle.

Yep, standard Crows Foot plug/receptacle. I'm surprised you have not seen them before. Very common on small 220 volt (yes, I said 220, since it is an old design ) single phase tools, like table saws, AC units, air compressors, pumps installed before the 80s.

 

[mbrooke]

Same reason legacy NEMA 10–30 outlets for 3-wire 230v Electric dryers are replaced by NEMA 14-30 outlets. NEMA 10 series is missing the grounding prong when neutral is used for control circuits.

Right, but you could ground through the neutral until 97. NEMA 10-15 dropped out the race before that.

 

[ramsy]

yes, thank you for refreshing my memory, 3-wire outlets for dryers are only allowed to be grandfathered on older properties and appliances.

 

[jeff48356]

yes, thank you for refreshing my memory, 3-wire outlets for dryers are only allowed to be grandfathered on older properties and appliances.

I always recommend to all my customers that they upgrade to 4-wire when they have 3-wire electric dryers and/or ranges. I explain that the 4-wire design is much safer than the old 3-wire. Since many people are afraid of electricity, most will go ahead with the upgrade. The only time I don't mention it is when upgrading will be difficult (such as finished walls or in homes without basements).