Which characteristic is essential for an enclosure to be considered watertight?

For an enclosure to be considered watertight, it is essential that it prevents moisture ingress under specified test conditions. This characteristic ensures that no water can enter the enclosure, thereby protecting any electrical components inside from damage due to moisture. The term "watertight" implies a stringent standard that is typically validated through specific testing procedures, which measure the enclosure’s ability to resist water ingress when subjected to certain environmental conditions.

The other characteristics listed—resisting dust and debris, withstanding high temperatures, and being made of non-conductive materials—are relevant to different types of enclosures or applications but do not directly pertain to the watertightness of an enclosure. While an enclosure may benefit from being resistant to dust, able to handle heat, or constructed from non-conductive materials, these factors alone do not ensure that the enclosure is watertight. Thus, the ability to prevent moisture ingress is the defining feature for classifying an enclosure as watertight.