What must be done before opening a series circuit?

Before opening a series circuit, it is crucial to drop the load and take the circuit out of service. This step is essential because, in a series circuit, the current flows through each connected component in sequence. If the circuit remains live while attempting to open it, there can be a risk of arcing, shock, or damage to equipment. By dropping the load and ensuring that the circuit is out of service, you eliminate the potential for any current to flow, thereby making the operation safer.

Specifically, taking the circuit out of service includes ensuring that any connected devices are not operational and that the circuit is isolated from its power source. This ensures that there is no voltage present in the circuit when work is being performed, which is a crucial safety protocol for linemen.

In contrast, while testing for voltage and disconnecting the power supply are important safety measures, they are typically performed after ensuring the load is dropped to confirm that the circuit is indeed safe to work on. Activating an emergency shutoff, while a good safety practice in certain situations, does not specifically address the need to first remove the load in a series circuit context.