What is the maximum fuse size recommended when using a double element time-delay fuse with a 20 amp motor?

The recommended maximum fuse size when using a double element time-delay fuse with a 20 amp motor is based on the nature of the motor's operation and the characteristics of the fuse. A double element time-delay fuse is designed to handle the inrush or starting current of motors, which can be significantly higher than the normal running current.

For a 20 amp motor, a common guideline is to allow for a maximum fuse size that is 125% of the motor's rated current. Calculating that, we have:

20 amps x 1.25 = 25 amps.

This value allows the motor to start without nuisance blowing of the fuse while providing adequate protection during normal operating conditions. Therefore, a fuse size up to 25 amps is appropriate.

Going beyond this size might increase the risk of overcurrent situations going undetected, which could lead to motor damage or failure. Hence, while choices exceeding 25 amps could be theoretically permissible in some contexts, for the safety and operational integrity of the motor, 25 amps is the maximum recommended fuse size under standard conditions.