Disconnect Rating

[Flapjack]

Article 430.110 (A) says a motor disconnect should be rated at no less than 115% of the motor's current rating.

I have a 30 HP sump pump motor that would be connected via plug and receptacle to a non-fusible disconnect switch with an interlocked arktite 3-wire, 4 pole receptacle. The OCPD is a 70A circuit breaker fed from an MCC.

Is it possible to use a 60A rated disconnect? I would think that the disconnect should be rated to at least the rating of the OCPD, but I can't find anything in the code that states that other than for snap switches.

 

[infinity]

The OCPD is larger than necessary to allow for the starting current of the motor. IMO for the same reason that the conductors are sized according to the motor load and not the size of the OCPD, would apply to the disconnect.

 

[masterinbama]

A safety switch is rated in HP. A Square D 600volt 60 amp non fused heavy duty safety switch is rated at 30HP. Your full load current from the NEC for that motor is 40 amps. 40 X 115% = 46. The non fused switch will work.

http://www.grainger.com/Grainger/SQUARE-D-Heavy-Duty-Safety-Switch-1H376?Pid=search