NM cable required to be secured to box

[Uncle Bob]

In 2006 IRC, E3805.3.2 and 2005 NEC, 314.17 ©; "All permitted wiring methods shall be secured to the (nonmetallic) boxes"; with the exception of nonmetallic boxes that are not larger than 2 1/4" X 4" nominal.

In other words; the cable is required to be secured to the box.

Electric nonmetallic box manufacturers use various different methods of supplying a "built in" plyable self-securing tab openings.

I find that in most instances these tab openings are "knocked out" and, rendered useless.

Here is a picture of a box with the "self securing tabs" punched out;

(right click on picture to enlarge)



Are you inspecting and enforcing this requirement?

Uncle Bob

 

[north star]

^ ^ ^

Uncle Bob,



Judging by the number of views vs. the number of replies, I'm

guessing that not too many of us knew about it, or either, ...do

not require the conductors to be secured to the non-metallic

junction boxes.

Can you please post some pictures of the non-metallic junction

boxes with conductors that ARE secured to them, so that the

viewing audience can have a visual example of the "correct

installation".

Thanks!



^ ^ ^

 

[vegas paul]

North Star - if the electrician simply leaves the tabs alone on the box shown in Bob's picture, the cable is secured (by friction and the angle of the edge) and everybody's happy. The problem is, most electricians treat the tabs as knock-outs and rip them off with a set of pliers, thus negating the designed purpose of them.

 

[Mule]

Yes we are enforcing it. That looks like one of those old style hard plastic boxes that have the screw clips on the inside to secure the wires. It would be a lot of trouble to break the tabs off a blue box. It would be more trouble than what it's worth.

 

[SCBO1]

Like VP states the electricain needs to leave the darn tab inplace. Have you every tried pulling the NM cable back out, almost impossible, thats why the tabs need to be there. I have seen this before, and thought I would be petty, enforcing this.

Another box thats a beige color (molded material) has to be punched out but there is a gray clip inside the box that when screwed down holds the NM cable in place.

Sometime you see those on the floor, if you do start looking for the boxes not having the clip.

Support Uncle Bob an Right em up!

pc1

 

[Uncle Bob]

North Star,

"Can you please post some pictures of the non-metallic junction

boxes with conductors that ARE secured to them, so that the

viewing audience can have a visual example of the "correct

installation".

I went out Sunday and tried to get some good pictures; but, they just didn't show well.

There are many variations. The problem is that it is difficult to force the cable through the slot; and the installers give up and knock out the securing tab.

Here are some written descriptions of the tabs;

1. A "V" shaped tab.

2. A flexible push tab; which you can render useless if you aren't careful.

3. A knock-out with a flexible securing tab "inside the box".

If they read the manufacturer's instructions (fat chance); they can become good at releasing the tab without damaging it. It just takes some practice.

Sorry about not having good pictures,

Uncle Bob

 

[Mule]

Sorry about not having good pictures,

Uncle Bob

You're fired!!

 

[north star]

* * *

Demerits issued to our Uncle! ....slacker !!

* * *

 

[Robert Ellenberg]

Different question regarding the same code requirement. You would not usually be using much conduit in residential wiring but there are situations where you need it for either protection, support or raceways. It appears the requirements for cable support and raceways are the same whether using metal or nonmetallic boxes and/or conduit.

For a new design where I am working on the details, I have assumed that I could use the blue flex pipe as a raceway at several locations that are going to have the NM box buried under foam insulation and fish the NM sheathed cable through the flex and staple it to the framing where it exits the flex. However, this requirement that Uncle Bob has pointed out for the NM sheathed cable to be attached to the NM box itself or within 8" of it seems to eliminate my ability to do that. However, if I read the code correctly, there is no similar requirement for a metal box. So if I read the code correctly I could mount a metal box and run the blue flex pipe to it as a raceway and where it exits the pipe continue to support the cable with staples,etc. until it terminates.

I don't think there is an intent to treat a NM box with conduit connected to it (as opposed to the cable entering a box without conduit) differently than a metal one in regard to securing the cable, but unless some of you can point out something I am missing in reading the code, that is what it appears to state.

 

[north star]

~ ~ ~ ~

Robert,

Have you looked at Section E3806.3 in the `06 IRC?

E3806.3 Metal boxes, conduit bodies and fittings.

"Where raceway or cable is installed with metal boxes, or conduit bodies,

the raceway or cable shall be secured to such boxes and conduit bodies."

Also, ...please , please, please, do not staple the conductors too tightly to

the wood framing elements. In this AHJ, I see a lot of instances where

the electrician has stapled the conductors so tightly to the framing that

the conductors cannot move around some. The staples are supposed to

be used as a guide only, and not like "super glue" to hold the conductors

in place. They also try cram as many conductors under that one staple

as they can. Please consider the heat dissipation factors when installing

the conductors. Thanks!

~ ~ ~ ~

 

[Robert Ellenberg]

Northstar--Thanks for the reply. I am aware of the stapling issue. My first real summer job in high school was as an electrician's helper and they drilled into my head to install staples very carefully and not to tight to the wires.

As to section 3806.3, the cable OR the raceway must be secured. In other words, I read it that if the conduit is secured to the box, the cable entering it does not have to be. But if it were plastic, that's different, even with conduit if I read it right.

 

[Uncle Bob]

Robert,

Maybe this will help with metal boxes;

2005 NEC, 314.17 (B) (too long for old man to type); but, yes the cable and/or conduit must be secured to metal boxes.

Hope this helps,

Uncle Bob

 

[raider1]

Northstar--Thanks for the reply. I am aware of the stapling issue. My first real summer job in high school was as an electrician's helper and they drilled into my head to install staples very carefully and not to tight to the wires.As to section 3806.3, the cable OR the raceway must be secured. In other words, I read it that if the conduit is secured to the box, the cable entering it does not have to be. But if it were plastic, that's different, even with conduit if I read it right.

There is no difference between using a mteal box or a plastic box that is listed for use with ENT (The blue smurf tube).

You are permitted to run NM cable in ENT into a plastic ENT box and secure the NM cable within 12" of where it exits the ENT provided that the sheath continues into the box at least 1/4" and there is a smooth fitting intalled on the end of the ENT where the NM cable enters.

334.15© In Unfinished Basements and Crawl Spaces.Nonmetallic-sheathed cable installed on the

wall of an unfinished basement shall be permitted to be

installed in a listed conduit or tubing or shall be protected

in accordance with 300.4. Conduit or tubing shall be provided

with a suitable insulating bushing or adapter at the

point the cable enters the raceway. The sheath of the

nonmetallic-sheathed cable shall extend through the conduit

or tubing and into the outlet or device box not less than

6 mm (1⁄4 in.). The cable shall be secured within 300 mm

(12 in.) of the point where the cable enters the conduit or

tubing. Metal conduit, tubing, and metal outlet boxes shall

be connected to an equipment grounding conductor complying

with the provisions of 250.86 and 250.148.

Chris

 

[Robert Ellenberg]

You all seem to be saying what I thought the intent was but I haven't seen code wording to match that intent and that is what I am searching for.

The above reference quoted by Raider1 refers to exposed basement walls and this will end up a concealed location. "secured" is not a term that I can find defined but I believed it to mean a clamp. Does having conduit attached to the box meet the requirment of "securing" the NM sheathed cable? If not, look back again UB's code quote that started this thread and tell me how you meet it with conduit coming into a NM box.

 

[raider1]

If not, look back again UB's code quote that started this thread and tell me how you meet it with conduit coming into a NM box.

You can not run conduit into a "NM Box". The design of an NM box is such that only a NM cable can be run into the box.

On the other hand using a plastic box designed for ENT would be legal.

There is nothing in 334.12 that prohibits NM cable from being installed in a raceway provided that the cable does not exceed the conduit fill requirements.

The example of 334.15© that I showed does not prohibit the installation of NM cable as specified where it is concealed. That section just permits this install for exposed work.

Chris

 

[Robert Ellenberg]

Raider1--Thanks for bearing with me. I am a builder/designer, not an electrician or code official.

Your response above seems to indicate that what you are calling a "NM Box" is a box designed for NM cable, regardless of whether it is plastic or metal. However, I can't find them defined anywhere and an example of boxes that take either would be Carlon's plastic handy box with an internal NM clamp and knock outs or a box with only knocks out with a cable clamp installed in it.

However, your explanation is exactly how I thought it was interpreted, I just found some of the wording to not be very clear.

Thanks again.

 

[raider1]

Raider1--Thanks for bearing with me. I am a builder/designer, not an electrician or code official.Your response above seems to indicate that what you are calling a "NM Box" is a box designed for NM cable, regardless of whether it is plastic or metal. However, I can't find them defined anywhere and an example of boxes that take either would be Carlon's plastic handy box with an internal NM clamp and knock outs or a box with only knocks out with a cable clamp installed in it.

However, your explanation is exactly how I thought it was interpreted, I just found some of the wording to not be very clear.

Thanks again.

When I said "NM Box" I was referring to a single or multigang plastic box with integral NM clamps in the box that does not have any standard knockouts that could be used to connect a conduit or raceway.

A carlon handy box with 1/2 ko's would be OK for use with cable clamps or conduit fittings.

Chris