How well do you know the Code? Think you can spot violations the original installer either ignored or couldn't identify? Here's your chance to moonlight as an electrical inspector and second-guess someone else's work from the safety of your living room or office. It's your turn to identify the violation.
Hint: In and out
Find the Answer
This NM cable has lots of sharp bends in it. Some of these bends appear to have kinked the cable, which could indicate that the cable jacket or the conductor insulation has been compromised. Bending NM type cable this sharply is a sure way to damage the wires.
According to Sec. 334.24, bends in NM cable must be made in such a way as to not damage the cable. The bending radius of the curve must be at least five times the diameter of the cable. For an example, if we use some typical manufacturer’s dimensions of 12/2 NM cable, we could say that the outside diameter of the smaller dimension might be approximately 0.16 in. Therefore, any cable bends in the smaller diameter would need a curve radius of 5 x 0.16 inches, or 0.8 in. This would be the equivalent of bending the cable around a 1.6 in. diameter ball. As you can see in the photo, the bends at the lowest portion of this cable are very sharp and have a bend radius that is much too small. In fact, these cables are bent at a 90 degree angle. This is not what you want to do when installing this type of cable.
Lastly, since this building is a store, Sec. 334.10(3) requires this NM cable to be concealed behind a 15-minute thermal barrier, such as ½-in. sheetrock.