What is the primary difference between Type NM cable and Type UF cable?

Type NM cable, also known as non-metallic sheathed cable, is specifically designed for use in dry locations. Its construction makes it unsuitable for exposure to moisture or damp environments, which could lead to insulation degradation and potential electrical hazards. This is why Type NM is typically used in applications such as residential wiring within walls and ceilings of dry interiors.

On the other hand, Type UF cable, or underground feeder cable, is designed for use in damp or wet locations. Its robust construction provides additional moisture resistance, allowing it to be used underground and in other conditions where it may be exposed to moisture. This makes UF cable suitable for outdoor applications, including feeder circuits to sheds or garages, or for direct burial in the ground.

Understanding the appropriate uses for each type of cable helps ensure safety and compliance with electrical codes, which is critical in construction and electrical work.