Hello everyone:
I’m specifying a 10KW/10KVA, 277V, Lighting central inverter. The inverter will be provided with (12) 20A/1P. In the past, for larger inverters, I used to specify a one output breaker and a separate fused coordination module (similar to Bussmann Quik-Spec fusible coordination panelboard) to provide the coordination required per NEC for emergency lighting. As we all know, the inverter doesn’t have enough fault current to trip the breaker upon short circuit conditions. I have seen some engineers in the past provided a large inverter to obtain more fault currents to be able to trip the breaker at fault condition which I think that’s not right to oversize the inverter for that reason. My questions:
1. Is the inverter designed, when specified with integral breakers, to include the selective coordination requirement per the NEC?
2. How can we deal with low magnitude fault currents when it’s on batteries? I don’t believe the NEC addresses this but isn’t better for the overcurrent devices to trip at fault condition when it’s on batteries?
thanks
I’m specifying a 10KW/10KVA, 277V, Lighting central inverter. The inverter will be provided with (12) 20A/1P. In the past, for larger inverters, I used to specify a one output breaker and a separate fused coordination module (similar to Bussmann Quik-Spec fusible coordination panelboard) to provide the coordination required per NEC for emergency lighting. As we all know, the inverter doesn’t have enough fault current to trip the breaker upon short circuit conditions. I have seen some engineers in the past provided a large inverter to obtain more fault currents to be able to trip the breaker at fault condition which I think that’s not right to oversize the inverter for that reason. My questions:
1. Is the inverter designed, when specified with integral breakers, to include the selective coordination requirement per the NEC?
2. How can we deal with low magnitude fault currents when it’s on batteries? I don’t believe the NEC addresses this but isn’t better for the overcurrent devices to trip at fault condition when it’s on batteries?
thanks