What is the maximum temperature rating for the conductors used in NM cables marked with "-B"?

• A. 60 degrees Celsius
• B. 70 degrees Celsius
• C. 90 degrees Celsius
• D. 100 degrees Celsius

Answer: (C)

The maximum temperature rating for conductors used in NM (Non-Metallic) cables marked with "-B" is 90 degrees Celsius. This designation indicates that the conductors are rated for higher operating temperatures, which is crucial for ensuring safe and efficient electrical performance. The 90 degrees Celsius rating applies to the conductors themselves, allowing them to carry more current without overheating compared to conductors rated for lower temperatures.

This higher temperature rating means that NM cables marked with "-B" are suitable for use in more demanding applications where increased thermal performance is needed. Understanding this rating is essential for anyone working with electrical wiring, as it influences the choice of cables for specific installations and helps prevent overheating and potential electrical fires in residential or commercial settings. Knowing the proper ratings also ensures compliance with electrical codes and safety standards.