What size Flexible Metal Conduit is required for a 14/2 NM cable containing three cables?

To determine the correct size of Flexible Metal Conduit (FMC) required for a 14/2 NM cable containing three conductors, it’s essential to consider the number and size of the conductors that will be housed within the conduit, as well as the National Electrical Code (NEC) guidelines.

When using 14/2 NM cable, which consists of two conductors and a ground wire, if three of these cables are being enclosed in the conduit, the total number of conductors amounts to nine (3 cables × 3 conductors each). The NEC provides a conduit fill calculation to establish the maximum number of conductors allowed in various conduit sizes to ensure safety and ease of installation.

For 14-gauge wire, the NEC recommends certain conduit sizes to avoid crowding and potential overheating. For multiple conductors, the conduit size must accommodate over three conductors, taking into account derating factors for heat dissipation.

Upon reviewing the fill capacity for FMC, a 1-inch conduit size is typically suitable for accommodating the nine 14 AWG conductors in a three-cable configuration without exceeding the NEC's requirements. This size allows for proper ventilation, reducing the risk of overheating, and provides sufficient space for wire movement during installation