Which IEC category is described as Distribution wiring including mains?

• A. III - Distribution wiring including mains
• B. I - Protected Electronic circuits
• C. II - Receptacle outlet circuit; plug-in loads
• D. IV - Origin of installation at the Utility level

Answer: (A)

This question tests how IEC installation categories are mapped to parts of a building’s electrical system. The phrase distribution wiring including mains refers to the wiring that carries power from the main service point through the building’s distribution network to outlets and loads—the interior wiring that includes the mains supply coming in.

That scope matches Category III, which covers distribution wiring including the mains. It sits between the mains origin at the service entrance and the consumer loads, distinguishing it from the other categories: Category I for protected electronic circuits (low-energy, isolated circuits), Category II for receptacle outlet circuits and plug-in loads, and Category IV for the utility-origin portion of the installation (service entrance and upstream).