The most common machine wiring insulation type used for motors is ______.

The most common machine wiring insulation type used for motors is ______.

• A. THHN
• B. XHHW
• C. NM-B
• D. THWN

Answer: (A)

Motor wiring requires insulation that can handle heat and still be flexible in dry, conduit-fed environments where motors and control panels reside. THHN, which stands for Thermoplastic High Heat-resistant Nylon-coated, is rated for 90°C in dry locations and has a tough nylon jacket that resists abrasion. This makes it durable for motor leads that must bend, flex, and fit into clamps and terminations inside panels. Its high temperature rating and ease of use in conduit systems make it the typical choice for machines. Other options fit different conditions: THWN is suited for wet or outdoor locations, XHHW is moisture-resistant and often used where moisture is a factor, and NM-B is intended for indoor residential wiring and not ideal for motor leads that require higher temperature ratings and greater flexibility.

Motor wiring requires insulation that can handle heat and still be flexible in dry, conduit-fed environments where motors and control panels reside. THHN, which stands for Thermoplastic High Heat-resistant Nylon-coated, is rated for 90°C in dry locations and has a tough nylon jacket that resists abrasion. This makes it durable for motor leads that must bend, flex, and fit into clamps and terminations inside panels. Its high temperature rating and ease of use in conduit systems make it the typical choice for machines. Other options fit different conditions: THWN is suited for wet or outdoor locations, XHHW is moisture-resistant and often used where moisture is a factor, and NM-B is intended for indoor residential wiring and not ideal for motor leads that require higher temperature ratings and greater flexibility.