Routing cables down an existing residential wall

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Mgarf33

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Ok, so if I'm understanding 300.4 exc-2 code correctly, it is allowable to fish a cable down an "existing residential structure" wall, say to a panel box with out the need to staple or route in conduit?
Obviously, we know it's more safe to route in semi-rigid conduit, but is it necessary?
What are your feelings on running a cable like NM-B to an existing panel, what do you typically do?
 
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Why do you feel it's more safe in conduit? And why would you need to secure cables inside an existing wall?


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Electricians have been snaking NM cable since it's invention doing so is not a problem. Part of the reason that we secure cables when the walls are open is to keep them from being damaged during the drywall installation.
 
brantmacga said:
Why do you feel it's more safe in conduit? And why would you need to secure cables inside an existing wall?


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Well, whether it be an exterior wall or interior wall, the likelihood of someone driving a nail is lower, I would hope, if they know there is a panel on the other side, but what if someone installs siding and decides to pop in a nail where the cable is touching the outside wall there is no protection.
 
Thank you both for the responses. I find myself always trying to make the job more difficult than it should be.
I'm still learning classroom hours can never be exchanged for OJT.
I figure it's easier to bug you all here than blowing up my old instructors phone every time I have an odd question.
 
Mgarf33 said:
Well, whether it be an exterior wall or interior wall, the likelihood of someone driving a nail is lower, I would hope, if they know there is a panel on the other side, but what if someone installs siding and decides to pop in a nail where the cable is touching the outside wall there is no protection.
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You try your best to install and make it as safe as possible. You really can NOT go with "What ifs" because "what if's" can make you go crazy.
 
Mgarf33 said:
Well, whether it be an exterior wall or interior wall, the likelihood of someone driving a nail is lower, I would hope, if they know there is a panel on the other side, but what if someone installs siding and decides to pop in a nail where the cable is touching the outside wall there is no protection.
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A fished-in cable is apt to move out of the way of a nail being driven into the wall.
 
infinity said:
Part of the reason that we secure cables when the walls are open is to keep them from being damaged during the drywall installation.
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^^^^^^
This- To the op: nm is basically secured to keep it of the way of the slings and arrows during construction.

edward said:
You try your best to install and make it as safe as possible. You really can NOT go with "What ifs" because "what if's" can make you go crazy.
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:thumbsup:

Smart $ said:
A fished-in cable is apt to move out of the way of a nail being driven into the wall.
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^^^^^^
This too-a loose cable will almost always jump back when struck with a nail. The jacket on modern nm, while not as hearty as its predecessors, is a little tougher than many think.
 
Mgarf33 said:
Well, whether it be an exterior wall or interior wall, the likelihood of someone driving a nail is lower, I would hope, if they know there is a panel on the other side, but what if someone installs siding and decides to pop in a nail where the cable is touching the outside wall there is no protection.
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You could see it as job security.:D

One of my biggest concerns is the finish nail gun on crown molding with 2.5" brads.
 
Knuckle Dragger said:
You could see it as job security.:D

One of my biggest concerns is the finish nail gun on crown molding with 2.5" brads.
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That will get both secured and non secured cables, If you want to protect from that possibility RMC is about as good as you are going to get for an approved wiring method.:happyyes:
 
300.4(A-2)

300.4(A-2)

"Where there is no objection because of weakening the building structure, in both exposed and concealed locations, cables or raceways shall be permitted to be laid in notches in wood studs or joists, rafters, or other wood members where the cable or raceway at those points is protected against nails or screws by a steel plate at least 1.6mm thick, and of appropriate length and width, installed to cover the area of the wiring. The steel plate shall be installed before the building finish is applied."

If protection against physical damage is to code, then damage from drywall installers is unlikely. Loose cables in the wall would then specifically not require additional protection, because they will move before being penetrated. The only way damage can take place is if they are anchored. So to a point, fishing non-protected wire is safer as it can flex and move itself away from damage. The only problem I could forsee, is a homeowner trying to do amateur electrical work, and yanking the conductors, causing a loose connection at the origin point.
 
Mgarf33 said:
Ok, so if I'm understanding 300.4 exc-2 code correctly, it is allowable to fish a cable down an "existing residential structure" wall, say to a panel box with out the need to staple or route in conduit?
Obviously, we know it's more safe to route in semi-rigid conduit, but is it necessary?
What are your feelings on running a cable like NM-B to an existing panel, what do you typically do?
Click to expand...

Nothing wrong with fishing cable down an existing wall. Leave some slack in the cable so that if it's hit with a nail or jab saw in the future, it moves instead of getting damaged. and do yourself a favor; drill larger than necessary holes in top/bottom plates, and, heaven forbid, any crossbraces you encounter mid-wall. It'd easier to fish and, near a panel, there may not be much room to drill another hole in the future should you need to add another cable or two. I always firestop vertical penetrations I make and usually do existing penetrations as well if in the same stud bay/area.
 
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