The DETD fuses installed in a safety switch supplied with 120/240-volt, 3Ø, 4-wire power can have a maximum rating of what amps?

The maximum rating for DETD fuses installed in a safety switch for a 120/240-volt, 3-phase, 4-wire power system is determined by the National Electrical Code (NEC) requirements for the ampacity of the conductors and the appropriate ratings corresponding to the protective devices used. In this case, the correct answer of 175 amps aligns with NEC standards governing fuse ratings for safety switches under these voltage and phase specifications.

Typically, safety switches and their associated fuses are limited to ratings that ensure safe operation without exceeding the capacity of the wiring or the load they service. The selected rating of 175 amps serves as a crucial protection measure to prevent overheating and potential damage to electrical components, adhering to accepted safety practices within electrical installations.

In this context, a higher ampacity rating such as 300, 225, or 200 may exceed the recommended specifications for such applications, and utilizing fuses above 175 amps could lead to safety hazards, including the risk of overloads or insufficient circuit protection. Thus, the safest and most compliant ampacity for DETD fuses in this application is rightly identified as 175 amps.