Exam question #2

[Chris13]

When using a NM KO plug in a metal box how far does it stick into the box? This is a question I could not come up with an answer from the NEC. 110.12A describes the opposite of what Im looking for. Any help would be appreciated!!

 

[Dennis Alwon]

Not sure what you are asking but art. 334 is for nm cable. Give it a look see and tell us what you found

 

[Chris13]

The question actually is referring to a plastic K.O seal in a metal box. Its asking for the depth that the plug sticks into the box.

 

[Chris13]

or how far it sticks out?? kind of a strange question im assuming something like 1/8" or 1/4"

 

[Little Bill]

Whose question is this, or who's asking it? Could you post the question exactly as written?

 

[augie47]

Sounds like a trick question. One could say 110.12(A) would not allow a plastic KO seal in a metal box.

 

[Little Bill]

Sounds like a trick question. One could say 110.12(A) would not allow a plastic KO seal in a metal box.

You may be partially right. I suspect that maybe the plastic seal might have been mentioned, but I suspect that they may have been referring to a plastic romex connector, which wouldn't have anything to do with what I think might have been the question.
I suspect the question might have been about the minimum amount of the sheath of NM cable that should enter the box past the connector. It just seems funny that the OP said the question was about NM cable and knock outs. This is my unpaid professional guess.

 

[resistance]

Sounds like a trick question. One could say 110.12(A) would not allow a plastic KO seal in a metal box.

I believe a NM seal is allowed in a metal box. 110.12(A) indicates: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.

 

[infinity]

I believe a NM seal is allowed in a metal box. 110.12(A) indicates: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.

Doesn't this say nonmetallic enclosures?

 

[WIMaster]

Whose question is this, or who's asking it? Could you post the question exactly as written?

Yes, if possible please post the question and possible multiple guess answers exactly as written.

This does sound like one of the trick questions on the WI masters of English and electricity exam.
It is multi. guess and some of the questions one needs to determine which is the "best" answer they want to hear as all the choices they give you may be right or all may be wrong, but which answer is "best". :rant:

 

[kwired]

When using a NM KO plug in a metal box how far does it stick into the box? This is a question I could not come up with an answer from the NEC. 110.12A describes the opposite of what Im looking for. Any help would be appreciated!!

I don't think most of the replies have understood the question.

Where do we come up with the question addressing NM cable? All it says is a NM KO plug? There are non metallic plugs that snap into standard raceway size holes, and are typically designed and probably listed for sealing holes in metallic enclosures. If it is listed for the purpose why should there even be any question of this nature?

A metal plug in a nonmetallic box is an entirely different issue.

If OP has accurate recollection of the question - it is a totally unacceptable question for exam purposes.

 

[infinity]

Since we're discussing a metal box with a plastic plug how do you get around the code section that Augie posted?

 

[Ponchik]

Sounds like a trick question. One could say 110.12(A) would not allow a plastic KO seal in a metal box.

110.12(a) says metallic plugs or plates with nonmetallic enclosures, it doesn't mention nonmetallic plugs with metallic enclosures.

these should be fine on metallic enclosures.

 

[kwired]

110.12(a) says metallic plugs or plates with nonmetallic enclosures, it doesn't mention nonmetallic plugs with metallic enclosures.

these should be fine on metallic enclosures.


View attachment 6774

The key part in 110.12(A) is "shall be closed to afford protection substantially equivalent to the wall of the equipment."

Then there is also a good chance the plugs you showed are a listed product and the listing includes closing holes in a metal enclosure. Without the listing they are not substantially equivelant to the wall of the equipment you are closing.

Good example of non listed plug that still meets 110.12(A) would be a metal enclosure with a metal bolt and fender washers closing a hole.

Potential violation may be stainless steel enclosure used because of corrosive environment and plugging the hole with a mild steel plug.