Journeyman Electrician Practice Exam

What is the maximum number of size 14 AWG THHN conductors permitted in a size 3/8 inch flexible metal conduit with a bare size 14 AWG grounding conductor?

1. 2

2. 3

3. 4

4. 5

The correct answer is: 4

The maximum number of size 14 AWG THHN conductors allowed in 3/8 inch flexible metal conduit is determined by the National Electrical Code (NEC) and the conductor fill requirements. According to NEC Table 1, for conductors installed in conduit, there are specific fill percentages that must not be exceeded based on the conduit size and the size of the conductors. In this case, a size 3/8 inch flexible metal conduit has a limited internal diameter, and size 14 AWG THHN conductors have a specific outer diameter. The NEC specifies that the maximum fill for conduits must be no more than 40% for one or two conductors and 30% for three or more conductors. When you take into account a bare size 14 AWG grounding conductor along with the THHN conductors, this influences the total number of conductors allowed. If we calculate based on the physical space required for the THHN conductors and the grounding conductor, it is possible to fit up to four size 14 AWG THHN conductors accurately, ensuring compliance with the NEC's fill requirements. Thus, the answer indicating that the maximum is four conductors is rooted in the specific allowances under the NEC for