MC cable fished in wood stud wall

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ZZZ

Member
I am needing to fish about a dozen lengths of MC down a wall for some outlet boxes. The wall is a display wall and it is about 8' tall in an area with a 10' ceiling grid. I would like to run some 1/2" emt along the 2x4 top plate of the wall and at each location where the wire will drop down I would like to install a 4-S box mounted with its back against the plate. I would need to bore a 1" hole in the plate to have room for the MC connector to fit through. I have not done this before and wanted to make sure there were no rules prohibiting this. Does anyone know of any problem with this? Thanks.
 

Howard Burger

Senior Member
I see a gap between top of wall and ceiling

I see a gap between top of wall and ceiling

I'm trying to visualize this wall. 8 foot high, ceiling 10 foot hight. 2 foot gap between top of - pony? - wall and ceiling. If I have this right, won't all your work show? How about fishing up from underneath? Or am I not seeing this correctly.
 

kwired

Electron manager
Location
NE Nebraska
Would you not need a strap within 12" of the box on the top of the wall?
Not when the cable is fished.

I'm trying to visualize this wall. 8 foot high, ceiling 10 foot hight. 2 foot gap between top of - pony? - wall and ceiling. If I have this right, won't all your work show? How about fishing up from underneath? Or am I not seeing this correctly.

I visualize a 8 foot wall with 2 more feet to the ceiling, he is running a raceway directly on top of wall with junction boxes at points where each drop inside of wall originates.

I see no problems with it if it is what I described.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
I would be concerned about a piece of MC dangling off the back of box with no support.

I know down inside the wall cavity you don't need to strap MC that has been fished. But up on top of the wall being discussed you have access and room to strap.
 

480sparky

Senior Member
Location
Iowegia
I would be concerned about a piece of MC dangling off the back of box with no support.

I know down inside the wall cavity you don't need to strap MC that has been fished. But up on top of the wall being discussed you have access and room to strap.

If the MC is connected to the box, and the box sits right on the top plate of the wall, there's no way to secure it unless you open the wall up.
 

kwired

Electron manager
Location
NE Nebraska
I would be concerned about a piece of MC dangling off the back of box with no support.

I know down inside the wall cavity you don't need to strap MC that has been fished. But up on top of the wall being discussed you have access and room to strap.

The wall is only 8 ft high, the cable is not exposed at all, the supplied outlet will provide some support also, just what are you concrened about? If this cable is going to try to go someplace where it should not, I don't want to know what size the cable actually is, gravity is about all there will be working on taking it down.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
I am needing to fish about a dozen lengths of MC down a wall for some outlet boxes. The wall is a display wall and it is about 8' tall in an area with a 10' ceiling grid. I would like to run some 1/2" emt along the 2x4 top plate of the wall and at each location where the wire will drop down I would like to install a 4-S box mounted with its back against the plate. I would need to bore a 1" hole in the plate to have room for the MC connector to fit through. I have not done this before and wanted to make sure there were no rules prohibiting this. Does anyone know of any problem with this? Thanks.

Would you not need a strap within 12" of the box on the top of the wall?

Dave, I don't think you have the right picture in mind. He is running along the top of the wall and setting the 4S on top with a hole bored for the MC connector, (see red above)

I would be concerned about a piece of MC dangling off the back of box with no support.


I know down inside the wall cavity you don't need to strap MC that has been fished. But up on top of the wall being discussed you have access and room to strap.


No where to strap it.

Move the box over.

That wouldn't accomplish anything, only cause more problems. He is going straight down the inside of wall from the 4S to the receptacle. This would be no different than dropping down from an attic.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Every time I have fished an MC down a wall I have strapped the cable coming out of the box above.

I am seeing a piece of MC dangling down a wall cavity to a cut in box with no support other than the fitting. It seems not right to me.

I have committed far greater sins against the code than this, so maybe getting hung up on this detail is my way of attempted atonement.
 

iMuse97

Senior Member
Location
Chicagoland
@ Action Dave: as I read the OP's description of the proposed job, the box will be mounted to the top plate of the wall, with a 1" (or a little larger) hole through the top in which he feeds the MC which connects to the back of the box that he fastens in place right over the hole.

If this is the scenario, I don't see how he could strap the MC unless he opened up the sheetrock above the ceiling height. Me? I wouldn't bother with that.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Every time I have fished an MC down a wall I have strapped the cable coming out of the box above.

I am seeing a piece of MC dangling down a wall cavity to a cut in box with no support other than the fitting. It seems not right to me.

I have committed far greater sins against the code than this, so maybe getting hung up on this detail is my way of attempted atonement.

This is not a "sin" against the code, it is permitted. 330.24(D)
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
@ Action Dave: as I read the OP's description of the proposed job, the box will be mounted to the top plate of the wall, with a 1" (or a little larger) hole through the top in which he feeds the MC which connects to the back of the box that he fastens in place right over the hole.

If this is the scenario, I don't see how he could strap the MC unless he opened up the sheetrock above the ceiling height. Me? I wouldn't bother with that.
I don't see how you can make a hole and then cover it up with a box and them claim inaccessibility.

Inspector- "You did not secure that piece of MC going into that box?" Was the place where it came through the top of the wall inaccessible?"

Electrician- "Yes sir. I screwed a 1900 box over the hole just to make sure."

Drill the hole above the stud cavity, place the box 1' or more away from the hole and strap the MC going into the box on the top.


This is not a "sin" against the code, it is permitted. 330.24(D)
Okay, if you are going to use 330(24)(D)(2) then I am going to have to give, but that limits the length of unsupported MC to six feet or less.
 

Volta

Senior Member
Location
Columbus, Ohio
I don't see how you can make a hole and then cover it up with a box and them claim inaccessibility.

Inspector- "You did not secure that piece of MC going into that box?" Was the place where it came through the top of the wall inaccessible?"

Electrician- "Yes sir. I screwed a 1900 box over the hole just to make sure."

Drill the hole above the stud cavity, place the box 1' or more away from the hole and strap the MC going into the box on the top.


Okay, if you are going to use 330(24)(D)(2) then I am going to have to give, but that limits the length of unsupported MC to six feet or less.

Hmm, I'm afraid you're right. There is no exception that I see for securing the cable within 12". The permission provided in 330.30(D)(2), wherein the MC fitting is allowed to serve as a support, doesn't seem to be what we need in general, and certainly not for this thread.

That would mean that installing a metal old-work box the way it is designed, and it is always used, is a violation. :(
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Drill the hole above the stud cavity, place the box 1' or more away from the hole and strap the MC going into the box on the top.


Okay, if you are going to use 330(24)(D)(2) then I am going to have to give, but that limits the length of unsupported MC to six feet or less.

He could so it this way but he's not required to do so. Fished, unsupported cable can be any length not just 6'. The goal here is to have the cable concealed which is permitted. The only way to secure it would be to open the wall and use a strap or a staple. That makes it's support impractical as outlined in 330.30(D)(1), part (2) would not apply to this installation. {2008}.

330.30 Securing and Supporting.
(D) Unsupported Cables. Type MC cable shall be permitted to be unsupported where the cable:
(1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impractical; or
(2) Is not more than 1.8 m (6 ft) in length from the last point of cable support to the point of connection to luminaires or other electrical equipment and the cable and point of connection are within an accessible ceiling. For the purpose of this section, Type MC cable fittings shall be permitted as a means of cable support.
 

Volta

Senior Member
Location
Columbus, Ohio
He could so it this way but he's not required to do so. Fished, unsupported cable can be any length not just 6'. The goal here is to have the cable concealed which is permitted. The only way to secure it would be to open the wall and use a strap or a staple. That makes it's support impractical as outlined in 330.30(D)(1), part (2) would not apply to this installation. {2008}.

And that will give us permission to leave the cable unsupported, yes.

Now, what allows us to leave it unsecured?
 
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