2 inverters, a XFMR, and NEC 690.9 (D)

[sokbok]

690.9(D) states that if the AC Disconnect on the utility side of the XFMR is appropriately sized, then no Disconnect is needed
between the inverter and the XFMR, which in our case is a 480Y to 208D, 175KVA.
But what about if there are 2 inverters feeding 1 transformer, combining on the lugs of the transformer?
My interpretation is that the code still reads the same and no AC disconnects are needed.
Any thoughts appreciated and yes I know the AHJ is who I need to ask.

thanks.

 

[electrofelon]

690.9(D) states that if the AC Disconnect on the utility side of the XFMR is appropriately sized, then no Disconnect is needed
between the inverter and the XFMR, which in our case is a 480Y to 208D, 175KVA.
But what about if there are 2 inverters feeding 1 transformer, combining on the lugs of the transformer?
My interpretation is that the code still reads the same and no AC disconnects are needed.
Any thoughts appreciated and yes I know the AHJ is who I need to ask.

thanks.

You restate 690.9(D) in quite different words, but upon thinking about it and reading it a bunch of times, I guess that is one way to put it (assuming "disconnect" is synonymous with "over-current protection")

You would basically never connect an inverter directly to a transformer considering 240.21(C). I would nearly always use a "combiner panel" on the inverter side of the transformer, with a main breaker to satisfy 240.21(C) and 408.36

 

[sokbok]

 

[GoldDigger]

Based on the principle that the limit on output current from the inverter protects the inverter, connecting wire, and transformer secondary from overload driven by the inverter.
While in the other direction the OCPD on the primary side protects the transformer from overload caused by a fault on the secondary side, including within the transformer, in the connecting wiring, and in the inverter.

 

[pv_n00b]

If the sum of the inverter maximum power outputs is less than the transformer rating then you do not need to protect the transformer from the inverters with over current protection. This has nothing to do with AC disconnects though. The transformer secondary conductors need to be installed in accordance with NEC 240.21(C).