pvgreeze
Member
- Location
- Philadelphia
- Occupation
- Electrical Engineer
Hello all...I'm working on a small genset project (not PV I know) where we are interconnecting on the load side of the service disconnect, so it follows the same principles of the PV designs I have worked on. This is an unusual site, as there is a large 400A panel directly adjacent to where we are installing our genset. The FLA of the generator is 276.6A, which at 125% is 345.8A, so a 400A OCPD. This is a peak shaving genset; no ATS or backup controls.
We had originally planned to interconnect on the MDP within the building at the opposite end of the bus, invoking 705.12(B)(2)(3). However, during a recent visit, our electrician noted the proximity of this panel and the fact that it was 400A as well. So, I'm trying to figure out why we couldn't just interconnect on the line side of this 400A MCB (protected inside by another 400A MCB). The interconnection would be from a fused 400A DS. The entire assembly would be outside as far as 240.21(B) goes, and the feeder would be protected at both ends. Seems like it shouldn't be an issue, unless I'm missing something major here. I've also attached a sketch SLD of the arrangement.
This post summed up what I'm explaining more or less; the exception being that all three OCPDs (A, B, and C) are all 400A here, and breaker B is already internalized as the MCB on the subpanel: https://forums.mikeholt.com/threads/nec-2020-705-12-b-1-feeder-vs-2-tap.2560100/post-2657874
We had originally planned to interconnect on the MDP within the building at the opposite end of the bus, invoking 705.12(B)(2)(3). However, during a recent visit, our electrician noted the proximity of this panel and the fact that it was 400A as well. So, I'm trying to figure out why we couldn't just interconnect on the line side of this 400A MCB (protected inside by another 400A MCB). The interconnection would be from a fused 400A DS. The entire assembly would be outside as far as 240.21(B) goes, and the feeder would be protected at both ends. Seems like it shouldn't be an issue, unless I'm missing something major here. I've also attached a sketch SLD of the arrangement.
This post summed up what I'm explaining more or less; the exception being that all three OCPDs (A, B, and C) are all 400A here, and breaker B is already internalized as the MCB on the subpanel: https://forums.mikeholt.com/threads/nec-2020-705-12-b-1-feeder-vs-2-tap.2560100/post-2657874
