What impact does installing multiple devices in a single box have on box fill calculations?

When installing multiple devices in a single box, each device is considered a conductor for the purpose of box fill calculations. According to the National Electrical Code (NEC), the box fill calculations are based on the number and size of conductors, devices, and equipment within the box.

Each device, whether it is a switch, receptacle, or another type of device, occupies space in the box as it adds to the total fill. Therefore, for accurate calculations, you must include all devices as conductors when determining whether the box is adequately sized to safely accommodate the wiring and devices. This ensures that the box is neither overcrowded nor violates the box fill limits set forth by the NEC, which is crucial for preventing overheating and ensuring safe electrical installations.