ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Is a line side interconnection feasible? If it is, it would render all of this moot.
I know there's wording on the 2020 code about these scenarios, but the 2017 doesn't touch on the feed through lugs situation. Now I have this inspector saying that the load center inside should be consider "part" of the MSP outside. So, according to him, whatever MCB I install at the load center inside should be included in the "....sum of overcurrent devices..." for the busbar outside where I'm installing my PV breaker. Am I missing something here?Yes. See 705.12(B)(2)(2).
The easiest way I've found around that situation is to add a main breaker to the subpanel, but it isn't possible in all situations.
Are you qualifying the outside MSP busbars under 705.12(B)(3)(3)? Can't you use 705.12(B)(3)(2), aka the 120% rule?I know there's wording on the 2020 code about these scenarios, but the 2017 doesn't touch on the feed through lugs situation. Now I have this inspector saying that the load center inside should be consider "part" of the MSP outside. So, according to him, whatever MCB I install at the load center inside should be included in the "....sum of overcurrent devices..." for the busbar outside where I'm installing my PV breaker. Am I missing something here?
His logic is correct, IMO.It's a 50A PV breaker, so I can't use the 120% rule. Option 705.12(B)(2)(3)(c) is the method that I'm trying to push. Either that, derate the main, or do a MSP upgrade. Currently it's a 200A MSP w/ a 200A MCB, and yes, the feed through lugs are in the opposite end of the MCB. If I follow this guy's logic, even if I tap the feed through conductors and slap a MCB at the load center inside, I would still be overloading the busbar outside.