Why must the installation be de-energized before conducting certain tests?

De-energizing the installation prior to conducting certain tests is essential primarily to ensure the safety of the tester and to protect the integrity of the installation. When electrical systems are live, there is a significant risk of electric shock, arcing, or other hazards which can be dangerous for personnel conducting the tests. By de-energizing the system, testers can work in a safe environment, minimizing the risk of injury.

Furthermore, de-energizing allows for accurate testing of the installation components without the interference of the live current, ensuring that any readings taken truly reflect the state of the wiring and connected systems. This practice not only prioritizes personal safety but also secures the integrity of the overall installation, as testing under live conditions could lead to false readings or inadvertent damage to sensitive equipment.