Using Table 430.52(C)(1), what is the maximum dual-element fuse size allowed for a 7.5-HP, 240-Volt, single-phase motor, assuming it will start and that sizing per 430.52(C)(1)(b) is not needed?

• A. 60 A
• B. 70 A
• C. 80 A
• D. 90 A

Answer: (B)

The key idea here is how the NEC determines motor overcurrent protection. For motors, the fuse size isn’t based on running current alone; it’s tied to the motor’s full-load current (FLC). The standard approach allows a fuse up to 250% of the motor’s FLC to accommodate the high inrush at startup while still protecting the conductors.

For a 7.5 HP, 240 V single‑phase motor, the FLC is about 28 A. Multiplying by 2.5 gives roughly 70 A. So the maximum allowed fuse size for this motor is 70 A, and a dual‑element (time‑delay) fuse is appropriate to tolerate the startup surge without nuisance tripping.

A 60 A fuse would be undersized compared to the 70 A maximum and could trip during startup, while 80 A or 90 A would exceed the NEC limit for this motor.