I am afraid I am making some clients spend more money than need to be and I could use clarification. Right off the bat - Question #1) Is the Tap connection a smarter or cheaper solution than the Feeder connection, in general?
My situation in which I think I am adding more equipment than necessary.
To the left, a 600 amp switch in a Service panel. To the right, (open door) 600 amp MLO. In the metal wireway, three #4/0 per phase. Due to constraints, we cannot have a supply side interconnect or a loadside interconnect into a busbar. The options are either a 705.12(B)(1)"Feeder" or a (B)(2) "Tap" Connection and it will occur in this metal wireway (~10% filled). The PV is 340 amps at 125%.
A search in all my Mike Holt PV books shows an image like the one below (from 2014 code, but same concept) and this is the Option (b) using OCPD instead of upgrading the Feeder Conductors.
Due to this past history with this Mike Holt inspired image, I thought, "let's add a new 600 amp OCPD and PV interconnect (with the Feeder conductors) on the Line Side Lugs of this new 600 OCPD. Then on the load side, the feeder conductors continue on to the existing MLO panel.
Question #2) Is this the most expensive design possible and should we simply install a 600 amp main into the MLO Square D panel and interconnect into the Line Side lugs?
I always interpreted "other than the opposite end of the feeder" to mean "Must Feeder Connect and not Tap Connect", but I now realize this a misinterpretation? This language is only in the (B)(2) Feeder section, and by definition, at least half the taps are in the middle of the feeder. Non?
To only mildly complicate this, it's a 208/120 service and the inverters are 480, thus we have a 208 Delta Primary (Utility) : 480/277 Wye Secondary (PV) Transformer right after the PV AC Disconnect. I understand the 10', 25' rules surrounding Taps and even 240.21(B)(3) Taps Supplying a Transformer, but perhaps I thought it wasn't the appropriate solution. I know designing using "Feeder" connections is sound, I just don't like the idea waisting clients money when I don't have to.
Thanks for analyzing this situation and I apologize if it's already been addressed in previous posts.
My situation in which I think I am adding more equipment than necessary.
To the left, a 600 amp switch in a Service panel. To the right, (open door) 600 amp MLO. In the metal wireway, three #4/0 per phase. Due to constraints, we cannot have a supply side interconnect or a loadside interconnect into a busbar. The options are either a 705.12(B)(1)"Feeder" or a (B)(2) "Tap" Connection and it will occur in this metal wireway (~10% filled). The PV is 340 amps at 125%.
A search in all my Mike Holt PV books shows an image like the one below (from 2014 code, but same concept) and this is the Option (b) using OCPD instead of upgrading the Feeder Conductors.
Due to this past history with this Mike Holt inspired image, I thought, "let's add a new 600 amp OCPD and PV interconnect (with the Feeder conductors) on the Line Side Lugs of this new 600 OCPD. Then on the load side, the feeder conductors continue on to the existing MLO panel.
Question #2) Is this the most expensive design possible and should we simply install a 600 amp main into the MLO Square D panel and interconnect into the Line Side lugs?
I always interpreted "other than the opposite end of the feeder" to mean "Must Feeder Connect and not Tap Connect", but I now realize this a misinterpretation? This language is only in the (B)(2) Feeder section, and by definition, at least half the taps are in the middle of the feeder. Non?
To only mildly complicate this, it's a 208/120 service and the inverters are 480, thus we have a 208 Delta Primary (Utility) : 480/277 Wye Secondary (PV) Transformer right after the PV AC Disconnect. I understand the 10', 25' rules surrounding Taps and even 240.21(B)(3) Taps Supplying a Transformer, but perhaps I thought it wasn't the appropriate solution. I know designing using "Feeder" connections is sound, I just don't like the idea waisting clients money when I don't have to.
Thanks for analyzing this situation and I apologize if it's already been addressed in previous posts.