I know the NEC volt drop is a FPN, however I need a little feedback on a particular future install. The customer has a shop which he will weld and use a air compressor along with lights and a couple small fan motors. The distance is 260 foot from panel to new 100 amp sub panel. My calculations @ 100 amps is a 16.6 volt drop (yikes) reduce the breaker to 60 amps and I get 9.9 volt drop. My question is what would you think the max volt drop should be?

My math: 2*K*I*L/CSA
2*21.2*100*260/66,360=16.6

Thanks H2O

Last edited by watersparkfalls; 02/04/14 09:27 PM.