I accidentally posted this in the wrong forum so I am re-posting it here. Feel free to close or move the tred.
when sizing grounding conductors for xfmr secondary conductors you size per nec 250.66, when you have mulitple sets of conductors you add the sum of the conductors, according to the 2005nec article 250.24(c).1 it indicates how to route and size, for conductors over 1100kcmil(copper) shall not have an ampacity of less than 12.5% of the largest service entrance phase conductor.
so for a 3000 amp service served with 8 sets of 600kcmil per phase is the following correct?
600*8 = 3250kcmil total per phase = 4800000 *.12.5% = 600000
so does this mean that the ground conductor shall be a 600kcmil per phase or is a 3/0 sufficent per the chart of 250.66??
The reply stated to see 250.102(c) but this reirates the same notion for phase conductors larger than 1100kcmil copper, that the grounding conductor shall not have an area less than 12.5% of the largest phase conductor. So like in the example stated above is the largest phase conductor, the sum of the paralleled conductors? Or is it the 600kcmil single conductor?
when sizing grounding conductors for xfmr secondary conductors you size per nec 250.66, when you have mulitple sets of conductors you add the sum of the conductors, according to the 2005nec article 250.24(c).1 it indicates how to route and size, for conductors over 1100kcmil(copper) shall not have an ampacity of less than 12.5% of the largest service entrance phase conductor.
so for a 3000 amp service served with 8 sets of 600kcmil per phase is the following correct?
600*8 = 3250kcmil total per phase = 4800000 *.12.5% = 600000
so does this mean that the ground conductor shall be a 600kcmil per phase or is a 3/0 sufficent per the chart of 250.66??
The reply stated to see 250.102(c) but this reirates the same notion for phase conductors larger than 1100kcmil copper, that the grounding conductor shall not have an area less than 12.5% of the largest phase conductor. So like in the example stated above is the largest phase conductor, the sum of the paralleled conductors? Or is it the 600kcmil single conductor?
