Which type of boxes should not be used where conduits or connectors requiring locknuts or bushings are to be attached?

The use of round boxes is discouraged in scenarios where conduits or connectors requiring locknuts or bushings are to be attached primarily due to their design. Round boxes typically lack the necessary flat surfaces to securely accommodate locknuts or bushings, which are square or rectangular in shape. These devices are meant to create a stable connection and seal between the conduit or connector and the box. If a round box is utilized in such situations, it may lead to a less secure installation, resulting in potential safety hazards, such as loose connections or even electrical faults over time.

In contrast, square, rectangular, and octagonal boxes offer the necessary surfaces and dimensions to effectively support locknuts or bushings. These types of boxes can accommodate the hardware required for secure connections, ensuring a reliable and safe electrical installation. Understanding the design and functional aspects of electrical boxes is essential for ensuring compliance with electrical codes and maintaining system integrity.