New York State Master Electrician Practice Exam

Which wire type is considered suitable for wet conditions?

1. THHN

2. THWN

3. RHH

4. NM

The correct answer is: THWN

The designation THWN stands for Thermoplastic Heat and Water Resistant Nylon-coated wire. This type of wire is specifically designed to withstand wet and damp conditions, making it ideal for application in areas where moisture may be present. The "W" in THWN indicates that the wire is rated for wet locations, which means it can handle exposure to water without compromising insulation integrity. In contrast, while THHN is often listed for dry locations, it does not have the added waterproofing features that THWN provides. RHH is designed for hazardous locations but isn't specifically rated for continuous exposure to moisture. NM, or non-metallic sheathed cable, is not suitable for wet locations due to its susceptibility to water damage. Therefore, THWN is the correct choice when considering wire type for use in wet conditions, as it not only maintains its performance in such environments but is also compliant with relevant electrical codes for safety and durability.