How must all metal raceways and boxes be joined together?

Joining all metal raceways and boxes must be done metallically to ensure a proper electrical connection and maintain the grounding continuity of the system. This method requires that the metal components are connected in a way that guarantees low resistance between them, facilitating effective grounding and ensuring the safety and reliability of the electrical system.

Metallic connections also help protect against issues such as corrosion and interference from electromagnetic fields, as these connections ensure that any electrical faults can be carried away safely. This is particularly important for maintaining safety standards and code compliance in electrical installations.

In contrast, insulated or plastic connections would separate the metal components electrically, which would not allow for effective grounding or bonding. Loose connections could lead to poor electrical performance or unsafe conditions, defeating the purpose of using metal raceways and boxes designed for durability and safety.