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 On Oct 12, 2010, at 6:25 AM, "Mark Frye" <ma...@berkeleysolar.com> wrote: > It doesn't sound like you have a "supply side connection". It sounds like you > have a "load side connection" which is upstream of the transfer switch but > still downstream of the service disconnect. > > Mark Frye > Berkeley Solar Electric Systems > 303 Redbud Way > Nevada City, CA 95959 > (530) 401-8024 > www.berkeleysolar.com > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Dave Palumbo > Sent: Monday, October 11, 2010 9:15 PM > To: 'RE-wrenches' > Subject: Re: [RE-wrenches] Supply side connection to a dedicated panel > > We are installing a 8kW grid tied PV system for a commercial client. There > is an auto start generator on the premises, therefore we will be utilizing a > supply side AC point of connection. Inverter is an SMA SB8000. System owner > plans on adding to system in the next few years. We are designing for a total > of 24kW of PV. > > > > We will install a 200A fused disconnect off the grid feed (line side of the > generator transfer switch). My plan is install a dedicated breaker panel for > the inverter 240VAC output(s). The SB8000 is rated at 29 Amps, so a 40A DP > breaker will do for the point of connection. This panel will eventually have > a total of (3) 40A DP breakers each with 8kW of inverter output. > > > > My question has to do with the interpretation of the 120 percent rule of the > rating of the busbar in the panel. Do I need to use a 225 Amp rated panel > with a downsized 150A main breaker? 225A busbar x 1.2 = 270 Amps -150A MB = > 120A total of inverter output allowed. Or, since this panel will only be used > for inverter AC point of connection, and not for loads, is it allowable to > label this panel as a “Dedicated Panel – connect no loads”. If that is the > case we could use a 200A panel, or even a 150Amp panel. A local electrician > proposed this “dedicated panel” to avoid the larger load center panel. I > cannot find any mention of “dedicated panel” in the NEC. > > > > I think what I am proposing follows 690.64. Any opinions, or advice would be > appreciated. > > > > Dave Palumbo > > Independent Power LLC > > www.independentpowerllc.com > > NABCEP Certified PV Installer > > Vermont Solar Partner > > 802.888.7194 > > > > > > > > > > > >
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