The largest permissible DETD fuse size with a line voltage of 480 volts would be?

To determine the largest permissible Disconnecting Energy Transfer Device (DETD) fuse size at a line voltage of 480 volts, it's essential to consider the National Electrical Code (NEC) guidelines pertaining to fuses and overcurrent protection. Specifically, for a three-phase system, there are established formulas and standards which dictate the allowable fuse sizes based on the continuous load that the equipment can handle.

In this context, the fuse size must align with NEC rules while considering the service rating and specific application of the circuit. The maximum size of a fuse used for overcurrent protection is generally sized to allow for a certain continuous load or a percentage of the equipment rating.

The answer of 25 is based on these considerations, as it is the largest permissible fuse size that would safely protect the equipment at 480 volts according to the NEC stipulations for typical applications. Choosing a fuse size larger than 25 may not comply with safety standards or equipment ratings, potentially leading to an inadequate protection scheme.

This determines safety and operational integrity, where the fuse should open under fault conditions but not interfere with normal operational currents. The other options, although they are close, do not meet the necessary requirements for safety and protection for a 480-volt system when applied to typical