Why NEMA 1-15?

[mbrooke]

Why did this becomes the dominant design standard?

https://www.reddit.com/r/electricians/comments/pcvss1

And not this?

https://www.reddit.com/r/electricians/comments/pdds69

There is a lot wrong with the prior having caused countless fires and electrocutions.

 

[hbiss]

Found in an older home. Why the extra horizontal opening on each side?​

That was a "combination" 120 and 240 (actually 110/220 back then) receptacle. It could be wired for either voltage and it will accept either plug. Unfortunately there was no way to keep a 110 volt plug from being plugged into it when it was wired for 220.

The bottom one is likely NEMA 10-20, 125/250. Two hots, neutral and no ground.

-Hal

 

[mbrooke]

That was a "combination" 120 and 240 (actually 110/220 back then) receptacle. It could be wired for either voltage and it will accept either plug. Unfortunately there was no way to keep a 110 volt plug from being plugged into it when it was wired for 220.

The bottom one is likely NEMA 10-20, 125/250. Two hots, neutral and no ground.

-Hal

The bottom is not a NEMA-10-20 since its rated 10/15 amps vs 20 amps.

But its rather telling that NEMA thought the EGC slot was good enough to act as a neutral...

 

[hbiss]

But its rather telling that NEMA thought the EGC slot was good enough to act as a neutral...

Well OK, similar to the 10-20.

There were few receptacles with EGC slots back then. So why wouldn't they use that spot for the neutral?

-Hal

 

[mbrooke]

Well OK, similar to the 10-20.

There were few receptacles with EGC slots back then. So why wouldn't they use that spot for the neutral?

-Hal

The pre NEMA 10/15, NEMA 10-20, NEMA 10-30 and NEMA 10-50 are all based on the same design, just increasing in size with current.


The EGC on Hubbel design came standard, where as EGCs were an obscure option on the NEMA design.

The EGC on the round grounding pin on the NEMA designs has a high probability of being compromised and much to high an R2 to be used as a neutral. And, if it has to high an R to be used a neutral, it ought not be used a ground either.

Grounding is an after thought on every NEMA receptacle, where as with the Hubbel design grounding was an integral characteristic.

 

[grich]

You can find plenty of the bottom receptacle in Australia.

OZ power plug

In the Wikipedia page, there's a link to a Hubbell patent for an Edison screw adapter to that plug, with a screw terminal to attach a grounding pigtail.

P&S still has the pictured receptacle in the catalog.

 

[yuhong]

AFAIK the bottom one was originally designed by Hubbell, and it is no coincidence that Australia decided to adopt it.

 

[mbrooke]

AFAIK the bottom one was originally designed by Hubbell, and it is no coincidence that Australia decided to adopt it.

Australia I think got it right.