A commercial building has a 400A, 480Y/277V, 3-phase, 4-wire service. The utility requires the service equipment to be located outdoors. The main service disconnect is rated for 400A. What is the maximum distance, in feet, that the service entrance conductors are permitted to run inside the building from the point of entrance to the main service disconnect, without additional protection?

Correct answer: A. 0 feet

According to NEC 230.70(A)(1), the service disconnecting means must be installed at a readily accessible location outside of a building or structure, or inside nearest the point of entrance of the service conductors. For service conductors that enter a building, NEC 230.6 (Protection Against Physical Damage) and 230.70(A)(1) combined with 230.72(C) (Grouping of Disconnects) imply that the disconnect must be immediately inside. There is no specific 'maximum distance' for unprotected service conductors inside a building, as they are generally required to terminate immediately at the service disconnect. Any length of unprotected service conductors inside a building is a hazard. The intent of the NEC is to minimize the length of unprotected service conductors inside a building. While some local jurisdictions might interpret 'nearest the point of entrance' to allow a very short distance (e.g., 5-10 ft) for practical installation, the strictest interpretation of the NEC for safety is 'as short as possible' or effectively 0 feet of *unprotected* run. The question specifically asks about 'without additional protection'. If they are unprotected, they must be immediately at the point of entrance. The best answer reflecting the NEC's intent to minimize this risk is 0 feet for practical purposes, meaning the disconnect should be at the point of entry. Any significant run would require methods of protection such as fire-rated construction or an immediate disconnect.