Ryan, I agree with you 100% with the caveat that it's a straight grid-tied PV system. A battery-backup system is a bit different. Loads are being transferred from the main service panel to the backup load panel. When there's no sun, the loads on the backup load panel are drawing from the grid. The feeders now have to be sized to handle the existing main service panel and the new backup load panel. In this scenario, theoretically 160A could be coming in on feeder cables rated for a 100A service.
Steven Lawrence ---------------------------------------------------------------------- Message: 1 Date: Wed, 31 Mar 2010 16:29:20 -0700 From: "Ryan LeBlanc" <r...@naturalenergyworks.com> To: <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] Supply Side Tap Overcurrent Protection Message-ID: <fcd090a6d57e4b7b9ec92ef6b1fb8...@rjlpc> Content-Type: text/plain; charset="us-ascii" Steven, A Line Side Tap, by nature, allows us 100% of the Service Entrance Conductor Ampacity. This typically ~equals Main Breaker rating, but is regardless of the Main Breaker rating or size of Loads, it's about the conductor. NEC recognizes that our systems produce power, not draw it, so downsizing the Main would have no effect on the size of a Line Side Tap. Corrected PV output is considered continuous, so if you have 100Amps worth of conductor, 100A worth of Loads (Coming), and 100A of Solar (Going), we're still considered square on that service conductor. Doesn't matter what the draw is in the panel, the remainder of energy goes out the meter. If you downsize the main, you are just missing out on that much load capacity. Downsizing Main breakers only assists Load Side connections, obviously by increasing the Main Panel to Main Switch ratio for 120% Rule math. Check out: Solar Pro SP2.4 Article "Can We Land: Means and Methods of Utility Interconnection." (LeBlanc/Yates) Available Free online at SolarPro's website. Ryan J. LeBlanc NABCEPT Certified Solar PV Installer Santa Rosa, CA Cell: 707.591.1950 Direct: 707.536.9839 r...@naturalenergyworks.com http://www.NaturalEnergyWorks.com _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
