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Old 01-22-2013, 11:53 PM   #1
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NM Cable Bend Radius


Upgrading/replacing wire throughout a 160+ year old home. We opened the pine plank flooring where the original electrical was added between 50-100 years ago (combination of K&T and old cloth covered 2 wire cable). Pulling the new NM/Romex cable through existing and new holes in the floor joists. When transitioning from going through the joist to run parallel to the joist do I need to leave some kind of slack for bend radius concerns or do I just staple it a few inches from the hole. We're following 2009 IRC here in WV.
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Old 01-23-2013, 06:47 AM   #2
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NM Cable Bend Radius


Id leave a little slack, maybe 6 inches then fold it over and staple it...better to be on the safe side...to answer the question, no there is no bend radius

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Old 01-23-2013, 07:09 AM   #3
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NM Cable Bend Radius


334.24 Bending Radius. Bends in Types NM, NMC, and NMS cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend during or after installation shall not be less than five times the diameter of the cable.
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Old 01-23-2013, 07:09 AM   #4
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Quote:
Originally Posted by Olsy View Post
to answer the question, no there is no bend radius
Of course there is... see my above post.
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Old 01-23-2013, 07:48 AM   #5
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NM Cable Bend Radius


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Of course there is... see my above post.
What i meant was its not a huge amount...so your right
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Old 01-23-2013, 07:57 AM   #6
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NM Cable Bend Radius


No you do not need to staple. Because it is a retrofit rewire. Now if you were gutting the walls, yes you would have to staple, but not in your case.
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Old 01-23-2013, 08:40 AM   #7
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NM Cable Bend Radius


How do you figure the diameter of the flat NM cable? Do I need to bring it across the bay to make sure there is enough or can I just leave a small slack bend before I staple it on the same joist that it comes through?
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Old 01-23-2013, 04:37 PM   #8
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NM Cable Bend Radius


i like to picture the size of a baseball. for 12/2 or 14/2 wire this shape would leave plenty of slack.
secure the wire after the bend
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Old 01-23-2013, 04:44 PM   #9
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NM Cable Bend Radius


Quote:
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How do you figure the diameter of the flat NM cable? Do I need to bring it across the bay to make sure there is enough or can I just leave a small slack bend before I staple it on the same joist that it comes through?
You use the largest dimension of the cross section. If it's 5/8" wide that is the number to use as a radius.
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Old 01-23-2013, 10:14 PM   #10
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This would be a good example ...
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Old 01-24-2013, 07:59 AM   #11
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NM Cable Bend Radius


I can't find any pictures of anyone doing it like you describe. The pictures that I can find on the web of a penetration of a joist or stud then change of direction with a staple they seem to have done it tight. See link below.

http://www.flickr.com/photos/25155538@N02/2516125035
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Old 01-24-2013, 10:19 AM   #12
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NM Cable Bend Radius


Also, holes through framing members are considered secured and supported of the cable.
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Old 01-24-2013, 09:52 PM   #13
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NM Cable Bend Radius


a bend radius is designed to give you the MAX amount you can bend it if you HAVE to. just make sure the wires are in a gentle curve, you are good to go. Never a flat 90 degree bend, that's all. Don't staple near holes, not necessary.
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Old 01-25-2013, 08:14 AM   #14
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NM Cable Bend Radius


Thanks for the input everyone. Based on the comments I'll make sure I don't pull the wires tight so that if during rough-in the inspector wants me to staple with the slack/bend radius, I can add them in. Seems to be consensus that I should not need them right at the hole though and that's really the only reachable place in the retrofit.

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