Well yes but, 690.64 (2) is titled and reads "Bus or Conductor Rating". The "or" is important and the 120% requirement does not apply to the upstream conductors, in this case. In general, if the sudpanel of 225A where backfeed with the 120A of PV and had a 150A breaker on its feeder from the main panel, the conductor between the main panel and the sub need be rated only for the 150A feeder conductor. The size of the feeder tap between the transfer switch lug and the new sub panel needs to be evaluated differently. I myself am a big fan of 240.21 (B), even when it comes to feeders with PV on them. I guess some folks are not, but other than the expression of opinion, I don't see anything to prohibits the use of downsized feeder taps in PV circuits. I think most folks would go for a downsized conductor to connect up the new subpanel, so long as it was located right next to the transfer switch equipment.
Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 <http://www.berkeleysolar.com/> www.berkeleysolar.com _____ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jason Szumlanski Sent: Tuesday, October 12, 2010 4:05 AM To: RE-wrenches Subject: Re: [RE-wrenches] Supply side connection to a dedicated panel That sounds right, which means that the existing wiring between the service disconnect and the transfer switch may also need to be evaluated since it will now have sources available at both ends. The rule applies to all bus bars and conductors "upstream" of the interconnection point as I understand it. Jason Szumlanski Fafco Solar
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