jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
JMHO the pre-2014 code requires you (for 120% rule and some other purposes) to sum the numeric values of the nearest OCPDs to the inverters, and as mentioned earlier, allows no leeway to do a vector addition. The sizes of the OCPDs are not vectors.
This is what we are discussing. So where does the 120% rule permit one to use the vector sum?
The OPs question wasn't about the 120% rule. Granted, he referred to conductor sizing, but he was really asking about the circuit current. Let's be definitive: in his example, it would be perfectly fine to use 50A (and thus 62.5A ampacity and 70A breaker), instead of 58A (80A breaker, etc.). No section of the code requires anything else.
If his AHJ then asks him to apply the 120% rule to the conductor and combiner, that's a new calculation, however you do it.