Under what condition may service switches be installed on the outside of a building?

Service switches can be installed on the outside of a building primarily for accessibility and safety reasons. The correct answer is based on the New York City Electrical Code, which allows this installation for buildings with a limited number of dwelling units.

When a building has four dwelling units or fewer, the likelihood of frequent access for utility personnel increases, justifying the placement of service switches externally. This arrangement ensures that power can be managed quickly and efficiently, which can be vital during emergencies or for routine maintenance.

In contrast, having a threshold of two dwelling units may not always warrant the same accessibility considerations as four units. Options indicating a maximum age of the building or the absence of additional floors focus on unrelated criteria, such as structural considerations or building code conditions, that do not directly impact the rationale behind placing service switches externally for operational efficiency.