Panelboard Load Calcs with Motors

[jcook980]

When calculating industrial/commerical panelboard loads, are the motor loads on the panelboard simply added together or is it the sum of all the motor loads plus 25% of the largest motor supplied by the panelboard? I am confused by 220.14 (C) which seems to indicate that the motor loads are calculated by the rules in 430 (430.22 and 430.24) concerning conductor sizing. I understand why motor conductors are increased in size by 125% but why aren't the motors simply added together to determine the panelboard load?

 

[charlie b]

220.14(C) tells us to calculate the motor per 430.22 and 430.24 (and one more place not related to this topic). But those two articles are about calculating the minimum ampacity of the conductors. So it doesn?t seem to make sense. All I can conclude is that they intend to have the amount of load that is included in the service (or feeder) calculation to be the same as the required ampacity of the conductors.