New York State Master Electrician Practice Exam

The correct reasoning for why service switches may be installed on the outside of a building when it has four dwelling units or less is rooted in safety and accessibility standards. When a residential building comprises four or fewer units, it is often considered less complex in terms of electrical service needs. This lower density allows for greater flexibility in service switch placement, while still prioritizing safe access for emergency personnel and utility workers.

External placements can facilitate quick disconnection in the event of an emergency, allowing firefighters and other first responders immediate access to the electrical service. Moreover, having a limited number of units simplifies compliance with local codes and regulations designed to enhance safety.

In contrast, the other conditions listed do not universally permit the installation of service switches outdoors. For instance, the height of the building or whether it has basement units can carry different implications for utility configurations, and the designation of the area as commercial might pertain to different regulations and service requirements. Thus, option A stands out as a specific scenario that aligns with building and electrical code regulations that consider both safety and practicality for smaller residential units.