Journeyman Electrician Practice Exam

For wiring in wet locations, which conductor insulation type is preferred?

1. THW

2. THHN

3. NM

4. UF

The correct answer is: THW

The preferred conductor insulation type for wiring in wet locations is THW. This is because THW insulation is specifically designed to withstand moisture and is rated for use in wet and damp environments. It has good water resistance and can maintain its protective qualities even in conditions where it is subject to direct exposure to water. In contrast, THHN is not suitable for wet locations, as it is designed primarily for dry environments and has a thermoplastic outer coating that may not hold up well under moisture. NM (Non-Metallic) cable is also not appropriate for wet locations because it is intended for dry, indoor use only and can suffer damage when exposed to moisture. UF (Underground Feeder) cable, while it can be used outdoors, is generally designed for direct burial and may not have the same level of moisture resistance as THW in certain applications. Thus, for wiring specifically in wet areas, THW is the optimal choice.