Bill K
Member
- Location
- United States
I have a commercial 480V project in which we need to tie a pair of PV inverter back feeds fused at 300A and a 150A respectively. Job is in excess of 350 kW total. We have nearby a pair of 400A and 200A existing ATS switches, each feeding main circuit breaker normal/emergency panels. The question arises as to whether we can add lugs into the normal/utility source terminals of each of these ATS switches, in compliance with 2014 NEC? We'd have no problem with the generator, as it would never see PV current. No backfeed issues. We are not passing PV and utility current in 2 directions, overloading any bussing. The ATS downstream feeder is protected by the served panel's integral main circuit breaker. The upstream ATS's utility side feeder breaker protects the feeder adequately. The PV feeder would be sized at the required 125% of inverter full current, and fused disconnects would be used to feed the PV feeder near the interconnection.
I guess the question is surrounding 705.12. It states to comply with either A,B,C -OR- D. We are greater than 100kW aggregate, so in my opinion, C applies, therefore A,B and D do not. And as such we have some leeway where to connect since the installation would be safeguarded and only operated by qualified persons.
So what I want to do, is connect at the ATS utility terminals with lugs without violating the UL listing (most ATS's have plenty of lug capacity) with the 2 feeds in these 2 existing ATS switches. The 150A feed would go to the 200A switch, the 300A to the 400A switch.
Seems to me, I don't have to comply with 705.12(D) Utility interactive inverters paragraph, since 705.12 gives one the option of complying with any (1) of the 4 options, and I comply with (C) already, so the more restrictive requirements in (D) are moot. Additionally, D has the requirement that the equipment backfed into, must be capable of serving MULTIPLE loads, which our ATS feeds only one, and so doesn't apply anyway to our case.
In any case, we are not passing the PV current through the ATS switches' bussing anyway, merely tapping ahead of the switch.
Thoughts on this approach would be most welcome.
I guess the question is surrounding 705.12. It states to comply with either A,B,C -OR- D. We are greater than 100kW aggregate, so in my opinion, C applies, therefore A,B and D do not. And as such we have some leeway where to connect since the installation would be safeguarded and only operated by qualified persons.
So what I want to do, is connect at the ATS utility terminals with lugs without violating the UL listing (most ATS's have plenty of lug capacity) with the 2 feeds in these 2 existing ATS switches. The 150A feed would go to the 200A switch, the 300A to the 400A switch.
Seems to me, I don't have to comply with 705.12(D) Utility interactive inverters paragraph, since 705.12 gives one the option of complying with any (1) of the 4 options, and I comply with (C) already, so the more restrictive requirements in (D) are moot. Additionally, D has the requirement that the equipment backfed into, must be capable of serving MULTIPLE loads, which our ATS feeds only one, and so doesn't apply anyway to our case.
In any case, we are not passing the PV current through the ATS switches' bussing anyway, merely tapping ahead of the switch.
Thoughts on this approach would be most welcome.
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