Hello all
We typically have an incoming service of 480 3 phase with a dedicated feeder transformer where we specify a grounded wye secondary connection. We run three phase conductors and a ground to a power panel or MCC, where we have breakers and starters for 3 phase motors. In addition, we have a breaker that feeds a lighting transformer. The secondary of the lighting transformer neutral is grounded and feeds a 120/240 single phase or 120/208 3 phase panel, depending on the requirements. We've been going back and forth whether we need a neutral on the 480 - the NEC implies yes but all the codebook examples are for a 3 phase 4 wire 120/208 service. I'm looking that it's essentially a 3 phase 3 wire service where a ground fault will trip a breaker - others in the office insist its a 3 phase, 4 wire that requires a neutral conductor in addition to a ground. Both would be bonded at both the transformer and in the panelboard/MCC. Any comments?
We typically have an incoming service of 480 3 phase with a dedicated feeder transformer where we specify a grounded wye secondary connection. We run three phase conductors and a ground to a power panel or MCC, where we have breakers and starters for 3 phase motors. In addition, we have a breaker that feeds a lighting transformer. The secondary of the lighting transformer neutral is grounded and feeds a 120/240 single phase or 120/208 3 phase panel, depending on the requirements. We've been going back and forth whether we need a neutral on the 480 - the NEC implies yes but all the codebook examples are for a 3 phase 4 wire 120/208 service. I'm looking that it's essentially a 3 phase 3 wire service where a ground fault will trip a breaker - others in the office insist its a 3 phase, 4 wire that requires a neutral conductor in addition to a ground. Both would be bonded at both the transformer and in the panelboard/MCC. Any comments?
