Under what conditions can Type AC cable be used?

Type AC (Armored Cable) is designed for specific environments and applications, which is why option C is the correct choice. It is primarily intended for use in dry locations where it is not exposed to moisture that could compromise its integrity. The exception noted for exposed vertical riser applications highlights that even in dry locations, care must be taken regarding how the cable is installed, particularly in vertical settings where moisture could potentially be present.

In residential installations, while Type AC cable can be used effectively in many scenarios, it is important to adhere to the guidelines regarding its usage in wet locations. Wet locations can pose significant risks, as moisture could lead to corrosion of the conductors and damage to the insulation, compromising the safety and performance of the electrical system. Therefore, options suggesting unrestricted use outdoors or in wet areas do not align with the specifications for Type AC cable.

Understanding these conditions ensures that the cable is used safely and effectively, adhering to the National Electrical Code (NEC) requirements.