Fastening romex

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  #1  
Old 10-23-00, 08:44 PM
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Is there a rule of thumb for how many cables you can fasten under one staple? When our house was built (3 years ago), we videotaped all the rough-in work. I was looking at the tape the other night and noticed there were several boxes with three or four cables under one staple. I'm now finishing the basement and doing the rough-in wiring, so that's why I'm curious.
 
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  #2  
Old 10-24-00, 06:32 AM
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There really is no rule of thumb, but you do want to make sure you can staple your wires neatly and that they will be held snugly to the stud. Make sure you staple the wires flat and not on thier edge. If you have any further questions you can visit my free message board at Natswift.com. I am a journeyman electtrician in two states and would be happy to help you in any way I can
 
  #3  
Old 10-24-00, 05:09 PM
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Yes there are rules for the installation of mounting non metalic sheathed cable.

110-3-b States that you must use the material as per the installation instructions of the manufacturer.

The manufacturer states the a # 10 wire staple is approved for use to support 2-12/2 or 2-14/2 Romexes or 1-12/3 or 1 14-3 romex or 1-10/2 or 1-10/3 romex. No larger non metallic sheathed cable is approved for support with a # 10 wire staple.

The manufacturer states that the white plastic two nail non metallic sheathed cable support is approved to support only 1-12/2 or 1-14/2 romex.

There are different sizes and designs of supporting devices to support non metallic sheathed cable [Romex].

310-15-b-2-a is a chart limiting the bundling of non metallic sheathed cable to three current carrying conductors if bundled more than 24" along the non metallic sheathed cable. Two-12/2 Romexes would be 4 current carrying conductors. What this says is if you bundle 2 non metallic sheathed cables up a stud under the same romex staple from a receptacle to the top plate, you are over the 24" limit and you must derate the ampacity of those cables as per the chart. As descibed up that stud the 2 Romexes rated 20 amps, bundled over 24" long will have the ampacity of those conductors reduced by that chart to equal 16 amps and you can no longer install a 20 amp breaker on those 12/2 romexes. If you bundled 4 romexes together as described below, more than 24" long up that stud under the same staple then your ampacity of those 4-12/2 romexes must be derated to 70% of their original amp rating making these 4-12/2 romexes only rated at 14 amps and you now are no longer allowed to use the above designed installation because the minimum amp rating of those 4-Romexes are not rated at the minimum rating of 15 amp conductors in the dwelling.

Hope this helps you design you wiring safely

Wg
 
  #4  
Old 10-25-00, 08:17 AM
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I agree with wg. Look at the box that the staples come in for this information. There are other types of device that allow you to support more than 1 cable. These stand-off type of devices are great things to use where space is limited, or if you have 3 or more cable to secure. Look at the hardware store for these items. The are fairly new, but are getting more and more common.

To wg, I hope the 1st poster decides to read these replies. I am thinking about going to his site to see if there is anymore mis-information.

Thanks for keeping him straight!

RM
 
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