What is the maximum size dual-element (time delay) fuse permitted to protect a feeder sized by section 230.24, which supplies the following group of no code letter, 230 volt single phase, squirrel cage induction motors?One 10 HP at 50 amperes and three 5 HP at 28 amperes.
Check my work. 240.62 says the protective device has to be sized to the largest motor in the group in accordance with 430.52. Article 430.52 says to use, in this case 430.52(C)(1) and the exception. Article 240.6 gives the standard amp ratings.
50 amps x 1.75 = 87.5amps. The overcurrent device to use would be 90 amps
90 amps + 28amps + 28amps +28amps = 171.5amps. The overcurrent device to use for all the motors would be 175 amps.