# Reason behind this code requirement



## Pharon (Jan 20, 2014)

Looks like it was first added to the 2002 NEC. No idea why, though.


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## 480sparky (Sep 20, 2007)

Pharon said:


> Looks like it was first added to the 2002 NEC. No idea why, though.


It was added to the 1937 NEC.


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## Pharon (Jan 20, 2014)

Just found this:

*Recessed plugs and plates*

_Can you give me an example of the meaning of the last sentence of 110.12(A) Unused Openings? Why shall metallic plugs or plates be recessed 1/4 inch from the outer surface?_

This requirement is applied only where metallic plugs or plates are used with nonmetallic enclosures. The requirement is to prevent inadvertent contact with an energized surface. While the requirement does not specify surface-mounted enclosures only, I believe this was the intent. The definition of enclosure does not include junction or outlet boxes. An example of the intent of this requirement would be a surface-mounted nonmetallic panelboard where the possibility of the metal plugs or plates becoming energized by contact with an energized conductor located in the panelboard is present. The metal plugs or plates would not be grounded (because the panelboard is nonmetallic) and would remain energized, presenting a shock hazard. Recessing the metal plugs or plates would help in preventing inadvertent contact with them.

http://www.ecmag.com/section/codes-...-overload-protection-electric-motors-and-more


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## Pharon (Jan 20, 2014)

480sparky said:


> It was added to the 1937 NEC.


Where was it in the 1999 NEC then? Because it wasn't in 110-12.


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## macmikeman (Jan 23, 2007)

Was there even such a thing as a non metallic electrical box back in 1937?


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## 480sparky (Sep 20, 2007)

macmikeman said:


> Was there even such a thing as a non metallic electrical box back in 1937?



Bakelite.


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## 480sparky (Sep 20, 2007)

pharon said:


> where was it in the 1999 nec then? Because it wasn't in 110-12.


370-18 .


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## BBS (Aug 19, 2009)

> Where metallic plugs or plates are used with nonmetallic enclosures, they shall be recessed at least 6 mm (1⁄4 in.) from the *outer* surface of the enclosure.





Pharon said:


> ...where the possibility of the metal plugs or plates becoming energized by contact with an energized conductor located *in* the panelboard is present.


The word of the rule and the explanation from ecmag seem contradictory.
Wouldn't a rule-compliant install, recessed into the the panelboard away from the *outer* surface, result in the plug being closer to the conductors *in* the panelboard?

The equivalent CEC rule is a bit more straightforward:


> 12-3024 Unused openings in boxes, cabinets, and fittings
> Unused openings in boxes, cabinets, and fittings shall be effectively closed by plugs or plates affording protection
> substantially equivalent to that of the wall of the box, cabinet, or fitting.


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## RIVETER (Sep 26, 2009)

Pharon said:


> Just found this:
> 
> *Recessed plugs and plates*
> 
> ...


I did not go to the link but I read your reasoning. Your's makes sense in a way but if someone is going to inadvertently stick a finger into an opening, or a depression they will go in AT LEAST, a quarter of an inch. It makes more sense to just not use a metal closure. Besides, apparently, the article "forgets" about the need to bond ALL metallic components of an electrical system.


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## papaotis (Jun 8, 2013)

good point, although a little rediculous


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## RIVETER (Sep 26, 2009)

papaotis said:


> good point, although a little rediculous


Your sentences should start with a capital letter.:thumbsup:


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## papaotis (Jun 8, 2013)

although i was very good at spelling, punctuation and most aspects of the english language i just dont care so much anymore jfyi! and wtf does it matter. so gfy!:laughing:


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## RIVETER (Sep 26, 2009)

papaotis said:


> although i was very good at spelling, punctuation and most aspects of the english language i just dont care so much anymore jfyi! and wtf does it matter. so gfy!:laughing:


I am right there with ya. i luv acronyms


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## BuzzKill (Oct 27, 2008)

regardless, water exposure? 
they wanted a tight fit and thought 6mm was better than 5mm..?


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## woodchuck2 (Sep 18, 2009)

So if you are correct then what we may see soon in the NEC is a requirement to have those plugs/plates bonded inside. Be an excuse for a money maker. Yes, it would be for safety too but what are the chances?????






Pharon said:


> Just found this:
> 
> *Recessed plugs and plates*
> 
> ...


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