Rule 2-034 and Bulletin 12-19-*

Questions have been asked regarding the number of NMSCs that may be supported by a cable staple.

Answer:

As per Rule 2-034 and Bulletin 12-19-*, cable staples are approved to support one cable only unless manufacturer documentation is provided to confirm certification for the fastening of more than one cable.

Note:

Please be aware that NMSC straps are available and certified for use for the support of two NMS cables stacked under one staple. This is acceptable where documentation from the manufacturer supports this practice. Examples of acceptable supporting documentation would include information on packaging or electronic or written information from manufacturer.

Tony Moscioni
Senior Electrical Inspector
Electrical Safety Authority

Note from Mike Holt:

The above information is from the Canadian Code, not the NEC, although the requirements are very similar. The NEC requires that Types NM and NMC Cable be secured and supported by staples, cable ties, straps, hangers, or similar fittings designed and installed so as not to damage the cable [334.30]. Although the NEC does not state the number of cables allowed to be secured by one staple or similar fitting, the product would need to be listed specifically for use with more than one cable [110.3(B)]. So be sure to read the manufacturer’s listing or labeling instructions and remember that conductors and equipment are acceptable under the NEC only if approved [110.2].  Also remember that if two or more NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation or through wood framing that is to be sealed without spacing between the cables, ampacity adjustment is required [334.80].