Jeff S
Member
- Location
- St. Louis, MO
I understand that for a single inverter, you would use the combined cm of the ungrounded DC conductors with table 250.66. Yes, I understand that 250.166 is for DC GEC but according to Soare's Book on Grounding, you should use 250.66. That said, if you have multiple inverters feeding a solar A/C combiner panel, do we need to combine all of the ungrounded DC conductors for table 250.66?
For example (4) #8 ungrounded conductors per inverter x 2 inverters would be 8 x 16,510cm=132,080. This would be equivalent to a 2/0 cable so from 250.66, the DC GEC would be a #4. This would be a commercial installation. It seems to me therefore that since we're using a combined DC/AC (larger of the two), the 125A solar A/C combiner panel will require a #4 Gnd to the main service panel.
I'm not looking to stir up the previously discussed threads regarding combined AC/DC GEC, just trying to know whether my thought process is correct in adding all of the ungrounded DC conductors. The alternative would be to just consider the conductors to each inverter.
Thanks,
J.S.
For example (4) #8 ungrounded conductors per inverter x 2 inverters would be 8 x 16,510cm=132,080. This would be equivalent to a 2/0 cable so from 250.66, the DC GEC would be a #4. This would be a commercial installation. It seems to me therefore that since we're using a combined DC/AC (larger of the two), the 125A solar A/C combiner panel will require a #4 Gnd to the main service panel.
I'm not looking to stir up the previously discussed threads regarding combined AC/DC GEC, just trying to know whether my thought process is correct in adding all of the ungrounded DC conductors. The alternative would be to just consider the conductors to each inverter.
Thanks,
J.S.