I'm asking the PV forum because of the nature of this project. This is in Texas, which is all NEC 2020 now. I will say, when we started this project, the particular city was in NEC 2014.
I have been engineering a bi-facial module "140" kW solar system for what seems like a year now, and am trying to get some clarification about an interconnect. I have designed it two ways: a supply side interconnect [705.11] into a new 1200 A Service Disconnect OR a load side interconnect into a feeder conductor [705.12(B)(1)(b)] from a Main Panel (listed as suitable for service disconnect) but without a service disconnect on the premises. Or at least, I and the Master Electrician have been saying there is no service disconnect means. Due to Covid, I have not inspected the sight in person only via facetime with the Master Elec. and the PV Install Company.
First, the details about the location. The service entrance conductors leave a 225 kVA, 208/120 Wye Secondary, Utility Transformer (with CT Meter) 10' from the building wall, go underground, and enter inside the building into the bottom lugs of an ITE 1200 ("suitable for service") switch distro board. There are 5 switches in this panel - two 600A Siemens Vacu Switches, one 300A switch, and two 200A switches. On the inside of the panel I can see "suitable for service" but none of the 5 switches have any such labeling. Let's say the original electrical install happened in the mid to late 70's as I see a stamp that says "inspected in 1974".
The big question - are these "service disconnects"??? In my opinion NO, this is main switch board whose bus bar and service entrance conductors has no OCPD, no fault protection, and no disconnecting means. Thoughts?
The City in question has a (and I'm paraphrasing) - if you supply side interconnect, you have to bring up all equipment up to NEC 2020. This is the route I am trying to make the clients (PV Install Company and Building Owner) take. Actually install a 1200 Amp service disconnecting means (with OCPD and rated for available AIC) and make the PV supply side interconnect into this new panel.
I have told the clients that I believe the install of a service disconnecting means is paramount to safety and my preferred design. BUT if those 5 switches are considered service disconnecting means, and the AHJ agrees that they are, then I will advise the clients to do a 705.12(B)(1)(b) Feeder Interconnect (which requires the install of a new 600 Amp fusible switch).
Last question: the PoCo told me the available fault current was 19,893 Amps at their transformer (and I calculated 19,721 Amps at the line side of the new service disconnecting means). Since I don't know the motor contribution, should I make worst case assumption and require the fuse or breaker rating to be 30,000 or 40,000 AIC without having done any calculations? Is there an accurate method for determining existing motor load as it pertains to calculating AIC? This building had a bunch of exhaust fans in a previous incarnation, but they have been taken off line.
PS the City has been a bit unresponsive to these "no service disconnect" inquiries (via email and phone), and so I look forward to your responses.
I have been engineering a bi-facial module "140" kW solar system for what seems like a year now, and am trying to get some clarification about an interconnect. I have designed it two ways: a supply side interconnect [705.11] into a new 1200 A Service Disconnect OR a load side interconnect into a feeder conductor [705.12(B)(1)(b)] from a Main Panel (listed as suitable for service disconnect) but without a service disconnect on the premises. Or at least, I and the Master Electrician have been saying there is no service disconnect means. Due to Covid, I have not inspected the sight in person only via facetime with the Master Elec. and the PV Install Company.
First, the details about the location. The service entrance conductors leave a 225 kVA, 208/120 Wye Secondary, Utility Transformer (with CT Meter) 10' from the building wall, go underground, and enter inside the building into the bottom lugs of an ITE 1200 ("suitable for service") switch distro board. There are 5 switches in this panel - two 600A Siemens Vacu Switches, one 300A switch, and two 200A switches. On the inside of the panel I can see "suitable for service" but none of the 5 switches have any such labeling. Let's say the original electrical install happened in the mid to late 70's as I see a stamp that says "inspected in 1974".
The big question - are these "service disconnects"??? In my opinion NO, this is main switch board whose bus bar and service entrance conductors has no OCPD, no fault protection, and no disconnecting means. Thoughts?
The City in question has a (and I'm paraphrasing) - if you supply side interconnect, you have to bring up all equipment up to NEC 2020. This is the route I am trying to make the clients (PV Install Company and Building Owner) take. Actually install a 1200 Amp service disconnecting means (with OCPD and rated for available AIC) and make the PV supply side interconnect into this new panel.
I have told the clients that I believe the install of a service disconnecting means is paramount to safety and my preferred design. BUT if those 5 switches are considered service disconnecting means, and the AHJ agrees that they are, then I will advise the clients to do a 705.12(B)(1)(b) Feeder Interconnect (which requires the install of a new 600 Amp fusible switch).
Last question: the PoCo told me the available fault current was 19,893 Amps at their transformer (and I calculated 19,721 Amps at the line side of the new service disconnecting means). Since I don't know the motor contribution, should I make worst case assumption and require the fuse or breaker rating to be 30,000 or 40,000 AIC without having done any calculations? Is there an accurate method for determining existing motor load as it pertains to calculating AIC? This building had a bunch of exhaust fans in a previous incarnation, but they have been taken off line.
PS the City has been a bit unresponsive to these "no service disconnect" inquiries (via email and phone), and so I look forward to your responses.