Which of these fuse ratings would be the best circuit protection for a motor rated at 20A full load ampere, FLA?

For circuit protection of a motor rated at 20A full load amperes (FLA), the best choice among the options provided is to use a fuse rating that is slightly higher than the motor's FLA to prevent nuisance blowing while still protecting the circuit from overloads and short circuits. Choosing a fuse rating that is too low could result in the fuse blowing during normal operation, especially under starting or transient conditions when motors typically draw more current.

In this case, a 25A fuse is appropriate as it offers a buffer above the motor's rated FLA, allowing the motor to start and run without repeatedly tripping the fuse for momentary current spikes, which are common during motor startup. This rating is in line with common practices where fuse ratings are typically set at approximately 125-150% of the motor's FLA to ensure reliable operation while still providing adequate protection.

Selecting a fuse with a rating much higher, such as 30A, would reduce its effectiveness in protecting the motor as it might not blow during a fault condition that could damage the motor. Thus, 25A serves as a balanced choice for protecting the motor while accommodating its operational characteristics.