Nec 300.4(d)

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erickench

erickench

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Okay, there is something about the above NEC section that does not make sense. How does a steel plate protect a cable that does not maintain a minimum 1-1/4" space from the edge of a framing member? I could understand if the cable was installed through a framing member. Then the steel plate would effectively protect it from nails. But how does it protect it if it's attached directly onto the framing member with absolutely no space but with less than 1-1/4" space from the nearest edge? What purpose does the steel plate serve and where would you install it? If the cable runs parallel at less than 1-1/4" from the framing member then the steel plate would have to be installed directly on the framing member between the framing member and the cable. I look at the pictures in Mike Holts books and the NEC handbook and it does'nt make any sense. The arrows indicate a space from a directly attached cable to the framing member but with 1-1/4" distance from the nearest edge.
 
I meant to say the arrows indicate the space between the edge of the framing member to a cable that is directly attached to the framing member. All the books seem to have this and I don't know why.
 
Stickboy, at the very top of the picture the arrows show a space between a directly attached cable and the edges. What is the purpose of this? How does this measurement determine on whether or not you need a steel plate? I could understand installing a steel plate between the cable and the framing member to separate it. This would surely protect against nails.
 
erickench said:
Stickboy, at the very top of the picture the arrows show a space between a directly attached cable and the edges. What is the purpose of this?
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You need 1 1/4" spacing on ceiling joist as well, (the nail plate would go on the BOTTOM of the joist, not the SIDE of the joist. :) ) if that ceiling were every sheetrocked, a nail/screw could easily hit a cable if it were not 1 1/4 away.


erickench said:
How does this measurement determine on whether or not you need a steel plate? I could understand installing a steel plate between the cable and the framing member to separate it. This would surely protect against nails.
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The NEC figures other trades will use the correct size nail/screw for the job, so 1 1/4 is sufficient for protecting the cable from being hit.
 
(the nail plate would go on the BOTTOM of the joist, not the SIDE of the joist. :) )

But what purpose would it serve if the nail plate was at the bottom of the joist? The cable is not inside the joist. It's running along side it in parallel.
 
erickench said:
(the nail plate would go on the BOTTOM of the joist, not the SIDE of the joist. :) )

But what purpose would it serve if the nail plate was at the bottom of the joist? The cable is not inside the joist. It's running along side it in parallel.
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You really think a nail/screw has never gone in at an angle? I understand what your saying, but in reality a nailplate would simple stop a nail/screw from hitting that cable.
 
Okay, you might have a problem if the nail went in at an angle. But personally I think that if it runs in parallel to the joist then the 1-1/4" rule should be strictly enforced with no exceptions otherwise you're going to have a pretty large steel plate. If the cable and the joist are at right angles then you would only need a small steel plate installed between them.
 
erickench said:
Okay, you might have a problem if the nail went in at an angle. But personally I think that if it runs in parallel to the joist then the 1-1/4" rule should be strictly enforced with no exceptions otherwise you're going to have a pretty large steel plate. If the cable and the joist are at right angles then you would only need a small steel plate installed between them.
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Actually is says the distance shall be maintained and steel plates can be used "where this distance cannot be maintained..."

Clearly your right and technically the steel plate can only be used when it's not possible to maintain the 1-1/4" IMO
 
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