Final answer:
The minimum size of rigid conduit for most installations is trade size 16 (1/2 inch), which is typically sufficient for residential and light commercial wiring. Conduit size selection must comply with the NEC and consider the type and number of wires, as well as installation conditions.
Step-by-step explanation:
The minimum size of rigid conduit allowed for most installations is a trade size 16 (1/2 inch). Conduit systems provide routing and protection for electrical wiring. While larger sizes such as 4-inch pipe and 8-inch pipe are common in industrial applications and offer economies of scale in the chemical industry, trade size 16 (1/2 inch) is often sufficient for typical residential and light commercial wiring needs. When selecting conduit size, it's important to ensure that the size is compliant with the National Electrical Code (NEC) and suitable for the type and number of wires being used, as well as the environmental conditions of the installation.
As with wire, the diameter of the conduit plays a significant role in its capacity. However, unlike wire gauges where larger numbers indicate smaller diameters, conduit sizes are directly proportional to their diameters. Therefore, a 16-inch pipe has a larger diameter than a 1/2 inch conduit. It's also important to note that while Table 7.15 compares pipes for economies of scale in the chemical industry, electrical conduits must also adhere to specific standards for safety and efficiency in electrical installations.