Matu
Member
- Location
- Washington, DC
- Occupation
- Solar Field Engineer
I'm currently working a project with service coming from a Siemens I-T-E FC-II switchgear rated at 1600A. The switchgear feeds a couple of sub panels, one of which is an 225A busbar rated MLO fed by a 125A main breaker in said switchgear. Using two SolarEdge 43.2kUS inverters, we have 300A of PV to interconnect.
One option I'm looking at is a load side tap on the busbar of the switch gear (probably have to confirm with Siemens first). However, this may not be possible.
My other option is performing a line side tap on a transfer switch (400A rated with a 400A busbar) but I don't think this is allowable anyway.
My third option is upgrading one of the 225A MLO to a 400A busbar to allow interconnection with the 300A of PV. This is obviously more costly, but something that can be considered. My question is whether this is allowable, as it would pass the 120% rule but would be feeding a 125A main breaker with 300A of PV. We've upgraded panels before, but never one where the main would be smaller than the inverter. If we went with this option and it was allowable, what additional considerations/adjustments should be made (Upgrading feeder conductors, etc.)?
One option I'm looking at is a load side tap on the busbar of the switch gear (probably have to confirm with Siemens first). However, this may not be possible.
My other option is performing a line side tap on a transfer switch (400A rated with a 400A busbar) but I don't think this is allowable anyway.
My third option is upgrading one of the 225A MLO to a 400A busbar to allow interconnection with the 300A of PV. This is obviously more costly, but something that can be considered. My question is whether this is allowable, as it would pass the 120% rule but would be feeding a 125A main breaker with 300A of PV. We've upgraded panels before, but never one where the main would be smaller than the inverter. If we went with this option and it was allowable, what additional considerations/adjustments should be made (Upgrading feeder conductors, etc.)?