michael1960
Member
- Location
- idaho
im confused!! I know 310.15 [4] [c] "clarifies " but im still way confused! its counted when greater than 50% of load is unbalanced. Which i think would mean a two hot plus neutral sub panel coming from that 4 wire 3ph main main panel.
but moving upstream how do you calculate feed to main panel. say a 100 amp 3 ph 4 wire 75 degree panel , you hope to use MC armored 1-1-1-1-4 alum XHHW 90 degree is 115 amps, but the termination is 75 degree main panel breaker so we use the 75 column- still ok at 100 amps. but would it be considered a ciircuit of 100 amps or less of AWG 1 or less and need to be sized from the 60 degree column? now termination is its a residential main panel is that considered mostly unbalanced and trigger counting the neutral as current carrying for an additional .80 reduction. this feeder getting bigger than the panel. im no engineer but wouldn't the neutral for this portion of the system be fairly balanced i would think the neutral could even be undersized a bit. I guess I just find it hard to believe a #1 aluminum isnt enough for a 100 amp panel.
but moving upstream how do you calculate feed to main panel. say a 100 amp 3 ph 4 wire 75 degree panel , you hope to use MC armored 1-1-1-1-4 alum XHHW 90 degree is 115 amps, but the termination is 75 degree main panel breaker so we use the 75 column- still ok at 100 amps. but would it be considered a ciircuit of 100 amps or less of AWG 1 or less and need to be sized from the 60 degree column? now termination is its a residential main panel is that considered mostly unbalanced and trigger counting the neutral as current carrying for an additional .80 reduction. this feeder getting bigger than the panel. im no engineer but wouldn't the neutral for this portion of the system be fairly balanced i would think the neutral could even be undersized a bit. I guess I just find it hard to believe a #1 aluminum isnt enough for a 100 amp panel.