Disconnect Size

[steve66]

Can I use a 30 amp non-fused disconnect for a 480V, 20 HP motor?

Per the NEC, the full load amps are 27A.

Or do I have to size the disconnect for 1.25 * 27 amps?

 

[jumper]

430.110 Ampere Rating and Interrupting Capacity.
(A) General. The disconnecting means for motor circuits
rated 600 volts, nominal, or less shall have an ampere rating
not less than 115 percent of the full-load current rating
of the motor.
Exception: A listed unfused motor-circuit switch having a
horsepower rating not less than the motor horsepower shall
be permitted to have an ampere rating less than 115 percent
of the full-load current rating of the motor.

 

[steve66]

430.110 Ampere Rating and Interrupting Capacity.
(A) General. The disconnecting means for motor circuits
rated 600 volts, nominal, or less shall have an ampere rating
not less than 115 percent of the full-load current rating
of the motor.
Exception: A listed unfused motor-circuit switch having a
horsepower rating not less than the motor horsepower shall
be permitted to have an ampere rating less than 115 percent
of the full-load current rating of the motor.

A 30 amp disconnect just misses the 115% rating, but it looks like the Square D disconnects are rated for 20 HP.