What type of copper wiring is referred to when discussing wiring installable in a residential service?

The correct choice refers to THHN/THWN copper wiring, which is specifically designed for use in residential services. This type of wiring is known for its versatility and is commonly used in both dry and damp locations, making it appropriate for various applications.

THHN stands for Thermoplastic High Heat-resistant Nylon-coated, indicating that it can withstand higher temperatures, while THWN indicates that it is also suitable for wet locations. This combination of features allows for the installation of this wiring in various settings within residential buildings, including both walls and ceilings, where consistent performance under varying conditions is crucial.

In contrast, THW is primarily used for wet locations but does not have the same heat-resistant properties as THHN/THWN, limiting its application in residential services. XHHW, which stands for Cross-linked High Heat-resistant Wire, is often used in industrial settings and may not be the optimal choice for typical residential installations due to its specific characteristics. NM-B, or Non-Metallic Sheathed Cable, while widely used in residential wiring, consists of conductors that may not provide the same level of heat resistance and moisture exposure as THHN/THWN when evaluating wiring for service equipment.

Thus, THHN/THWN wiring emerges as the superior