I would like to get your help with the NEC section 705.95(B) Neutral Conductor for Instrumentation, Voltage Detection or Phase Detection. Since most 3-phase inverters do not run current through the neutral in the output circuit, this code makes good sense. However, in section 705.95(B) there is not the same exception as in section 215.2(A)(1), which states, “The size of the feeder circuit grounded conductor shall not be smaller than that required by 250.122, except that 250.122(F) shall not apply where grounded conductors are run in parallel.”
With that said, when sizing the neutral where 705.95(B) applies and the inverter 3-phase output circuit is made of parallel runs, can we apply sections 215.2(A)(1) and 310.10(H) to this circuit?
For example, let’s use the circuit between a 1200A inverter breaker and the utility-interactive inverter. Using Table 250.122, a 1200A overcurrent protection device (OCPD) requires an EGC size of a #3/0 AWG copper conductor. Since four parallel raceways are used, we need to divided the cross sectional area of the #3/0 AWG by 4 to determine the minimum cross sectional area for the four parallel grounded conductors, where #3/0 AWG = 167.8 kcmil.
167.8 kcmil /4 = 41.95 kcmil.
Since #1/0 AWG (105.6 kcmil) is the minimum size for a grounded conductor to be run in parallel per 310.10(H) and #1/0 AWG is greater than the required size for each of the four runs, is a #1/0 AWG grounded conductor code compliant in this example?
With that said, when sizing the neutral where 705.95(B) applies and the inverter 3-phase output circuit is made of parallel runs, can we apply sections 215.2(A)(1) and 310.10(H) to this circuit?
For example, let’s use the circuit between a 1200A inverter breaker and the utility-interactive inverter. Using Table 250.122, a 1200A overcurrent protection device (OCPD) requires an EGC size of a #3/0 AWG copper conductor. Since four parallel raceways are used, we need to divided the cross sectional area of the #3/0 AWG by 4 to determine the minimum cross sectional area for the four parallel grounded conductors, where #3/0 AWG = 167.8 kcmil.
167.8 kcmil /4 = 41.95 kcmil.
Since #1/0 AWG (105.6 kcmil) is the minimum size for a grounded conductor to be run in parallel per 310.10(H) and #1/0 AWG is greater than the required size for each of the four runs, is a #1/0 AWG grounded conductor code compliant in this example?