I had someone ask me about a novel way of complying with the 120% bus loading 2014 NEC requirement for a load side interconnection.
They have a large switchboard and a large PV system. The PV system back feed current multiplied by 1.25 plus the main OCPD rating would be over 120% of the bus rating for a load side interconnection. The PV back feed current by itself is less than 80% of the main OCPD and bus rating so that's not an issue.
They proposed putting in a current sensing (52) protection relay system that would monitor the current in the main OCPD coming into the switchboard and the current from the PV system (multiplied by 1.25 of course), sum them and if the value reached 120% of the bus rating the relay would trip the PV back feed breaker. This would comply with the intention of the NEC, but not the specific wording of 705.12(D)(2).
Assuming the AHJ would accept this any thoughts on the whole idea?
They have a large switchboard and a large PV system. The PV system back feed current multiplied by 1.25 plus the main OCPD rating would be over 120% of the bus rating for a load side interconnection. The PV back feed current by itself is less than 80% of the main OCPD and bus rating so that's not an issue.
They proposed putting in a current sensing (52) protection relay system that would monitor the current in the main OCPD coming into the switchboard and the current from the PV system (multiplied by 1.25 of course), sum them and if the value reached 120% of the bus rating the relay would trip the PV back feed breaker. This would comply with the intention of the NEC, but not the specific wording of 705.12(D)(2).
Assuming the AHJ would accept this any thoughts on the whole idea?