Why are disconnect switches installed in series with circuit breakers?

Disconnect switches are installed in series with circuit breakers primarily to isolate the breaker for service. This configuration enables maintenance personnel to safely work on the circuit without the risk of electrical shock or accidental re-energization. When the disconnect switch is opened, it disconnects the load from the power source, effectively isolating the entirety of the circuit, including the breaker itself. This makes it possible for technicians to inspect, repair, or replace the circuit breaker without the danger of live electrical currents.

While improving circuit efficiency and allowing remote operation may be additional benefits in some cases, the primary purpose of the disconnect switch in this context is to ensure safety during maintenance activities. It provides a clear visual indication that the circuit is de-energized, which is a critical safety measure. Additionally, disconnect switches do not enhance safety during overloads; instead, their role is primarily about isolation for servicing purposes.