What is the maximum number of No. 14 AWG THHN copper conductors allowed in 3/8-inch flexible metal conduit using external clamp-type fittings?

The question revolves around the conduit fill capacity, which is determined by the size of the conduit and the type and gauge of conductors being used. For 3/8-inch flexible metal conduit, the maximum number of conductors is calculated based on the NEC (National Electrical Code) requirements for conduit fill.

When dealing with 14 AWG THHN copper conductors, each conductor occupies a specific amount of space within the conduit. The code provides tables to determine how many conductors can fit into a conduit without exceeding fill limits and ensuring the conductors can be safely installed.

For a 3/8-inch flexible metal conduit, commonly used in various wiring applications, it can typically accommodate a specific number of conductors based on their size. The standard calculations reflect that up to four No. 14 AWG THHN conductors can fit safely within this conduit, allowing for proper heat dissipation and ease of installation.

These calculations take into account the total cross-sectional area of the conductors and the minimum fill requirements to avoid overcrowding, thus leading to the conclusion that the maximum number of No. 14 AWG conductors allowed in a 3/8-inch flexible metal conduit, when using external clamp-type fittings, is indeed four.