In a two-family dwelling, is equipment that supplies an individual dwelling unit allowed to supply branch circuits used for lighting in the public or common area?

• A. Yes, it's allowed
• B. No, it's prohibited
• C. Only with owner consent
• D. Only for temporary installations

Answer: (B)

The important idea here is that circuits serving a dwelling unit must be kept separate from circuits that serve the building’s public or common areas. Public and common-area lighting needs to be fed from a circuit that is independent of the individual unit’s distribution so it can be maintained and operated without being affected by one unit’s wiring or occupancy. This separation also helps prevent backfeeding or intermingling of loads between units, and ensures that the building’s shared spaces can remain lit and controllable even if one unit has issues or is de-energized. Because the equipment that serves a single dwelling unit is intended only for that unit, it is not allowed to supply branch circuits used for lighting in the public or common areas.