Journeyman Electrician Practice Exam

What is the minimum allowable trade size IMC required for ten copper THW conductors?

1. 2 inches

2. 2 1/2 inches

3. 3 inches

4. 3 1/2 inches

The correct answer is: 2 1/2 inches

When determining the minimum allowable trade size for Intermediate Metal Conduit (IMC) used for ten copper THW conductors, it's essential to refer to the National Electrical Code (NEC) tables, particularly Table 1 in Chapter 9, which addresses the conduit fill requirements. For copper conductors, the NEC considers the diameter of the conductors and the maximum fill capacity of the conduit. The maximum fill percentage for a conduit with multiple conductors generally cannot exceed 40% of the total conduit cross-sectional area to allow for heat dissipation and to ensure safe installation. In this case, if we assess the appropriate conduit size for ten copper conductors, the specified number of conductors requires a minimum conduit size that allows them to fit comfortably within the confines of the conduit while adhering to the NEC's fill requirements. Choosing a size that is adequate ensures safety and compliance. The correct answer is based on the specifications of each conduit size and their respective fill capacities calculated from the NEC tables. For ten copper THW conductors, a trade size of 2 ½ inches is determined to be the minimum allowable size, as it accommodates the required number of conductors without exceeding the fill limit, providing ample space for heat dissipation and effective operation.