How must a service disconnect function in relation to conductors?

The correct answer is that a service disconnect must operate simultaneously with respect to the conductors. This requirement is essential for ensuring the safety of both electrical workers and the general public during maintenance or emergency situations.

When a service disconnect is activated, it needs to interrupt the electrical supply to all conductors that could pose a hazard. If the disconnection were to happen sequentially, there could be a risk of live conductors still posing a shock hazard or causing an arc flash, leaving the system in a potentially dangerous state during maintenance.

The simultaneous operation guarantees that all circuits are effectively isolated from the power source at the same time, creating a safer environment for any work that needs to be conducted, such as repairs or inspections. This practice is in line with the National Electrical Code (NEC) requirements, which emphasize safety through immediate disconnection of all energized parts.