When bending Type NM cable, the tightest bend permitted by the NEC has a radius of ___.

When bending Type NM cable, the tightest bend permitted by the NEC has a radius of ___.

• A. 5 or less times the diameter of the cable
• B. 5 or more times the diameter of the cable
• C. 5 or more times the radius of the cable
• D. 5 or less times the radius of the cable

Answer: (B)

Bending NM cable requires a fairly generous bend to protect the insulation and avoid stressing the conductors. The standard rule is to treat the minimum bend radius as five times the cable’s overall diameter. Using the cable’s diameter (not the conductor radius) keeps the bend large enough to prevent deformation of the sheath and damage to the inner wires as the cable is routed around corners or past boxes. For example, if the NM cable has a diameter of about 0.4 inches, you should aim for a bend radius of at least 2 inches. Choices that imply bending with a radius based on the radius (which would be smaller) or using a smaller multiple would not meet the code requirement and could lead to damage.

Bending NM cable requires a fairly generous bend to protect the insulation and avoid stressing the conductors. The standard rule is to treat the minimum bend radius as five times the cable’s overall diameter. Using the cable’s diameter (not the conductor radius) keeps the bend large enough to prevent deformation of the sheath and damage to the inner wires as the cable is routed around corners or past boxes.

For example, if the NM cable has a diameter of about 0.4 inches, you should aim for a bend radius of at least 2 inches. Choices that imply bending with a radius based on the radius (which would be smaller) or using a smaller multiple would not meet the code requirement and could lead to damage.