What insulation rating is indicated by NM cables marked with "-B"?

NM cables, also known as non-metallic sheathed cables, are commonly used in residential and light commercial electrical wiring. The insulation rating marked with "-B" specifically indicates that the cable is rated for a maximum operating temperature of 90°C. This is particularly relevant when considering the environment in which the cable will be installed, as higher rated insulation can help improve the safety and performance of the electrical system, especially in situations where cables may be bundled together or installed in areas with limited airflow.

The 90°C rating allows for greater flexibility in design and installation, as it provides more tolerance for potential heat generated by the current flowing through the conductors. Understanding these ratings is essential for ensuring compliance with electrical codes and for maintaining the longevity and safety of electrical installations.