davedottcom
Senior Member
I understand the sum of all breakers feeding the busbar can't exceed 120% of the busbar's rating in a single phase situation, but shouldn't it be different in a 3-phase situation? If you have (3) 2-pole breakers back feeding a 3-phase panel. Let's say (3) 2-pole 40's on a 200 amp 3-phase panel w/ 150 amp main breaker.
200 amp x 120% = 240 Amps
150+40+40+40= 270 Amps (Too much)
But since the 2-pole breakers only land on each phase twice shouldn't it be:
150+40+40= 230 Amps
200 amp x 120% = 240 Amps
150+40+40+40= 270 Amps (Too much)
But since the 2-pole breakers only land on each phase twice shouldn't it be:
150+40+40= 230 Amps