Alan,
Thanks for the clarification. I believe you and Jeremy are talking about the exception listed on the last paragraph of 705.12(D)(2). I've never used that rule but it is good to know about. When we do battery backup we typically route the critical loads through an external transfer switch rather than through the battery inverter but this definitely has the potential to open up doors and potentially reduce equipment cost. Best, August August Goers Luminalt Energy Corporation 1320 Potrero Avenue San Francisco, CA 94110 m: 415.559.1525 o: 415.641.4000 aug...@luminalt.com *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Allan Sindelar *Sent:* Wednesday, February 27, 2013 4:08 PM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] Conductor Sizing for Supply Side Connection August, The 60A breaker is intended to allow grid power to pass through to the loads in excess of the inverter's stand-alone output. The point of 705.12 (moved in the 2011 NEC from 690.64 (B)(2)) is to differentiate between load pass-through current and sell current. The amount of current fed into the grid is (4500/230 =) 19.56A, while the amount that can be taken from the grid and passed through to the load is much greater. If you were limited to a 40A breaker in order to maintain 120% of a 200A main bus, you'd be prone to nuisance trips under large cumulative loads. Allan *Allan Sindelar* al...@positiveenergysolar.com NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder and Chief Technology Officer *Positive Energy, Inc.* 3209 Richards Lane (note new address) Santa Fe, New Mexico 87507 *505 424-1112* www.positiveenergysolar.com On 2/27/2013 4:23 PM, August Goers wrote: Jeremy, Good point. Even under the 2008 NEC 690.64(B)(2) you can install up to a 40 Amp breaker on the load side as long as it is on the opposite side of the input feed per 690.64(B)(7). Garrison, do you need a 60 A breaker? I haven't used this product myself, but if the continuous output power is indeed 4500 W then you'd be fine with a 25 or 30 A breaker. Best, August *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *All Solar, Inc. *Sent:* Wednesday, February 27, 2013 1:50 PM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] Conductor Sizing for Supply Side Connection There is an exception in NEC2011 regarding the point of connection. This may not apply, but you could avoid the supply side. 4500W / 240V = 18.75 x 1.25 = 23.4A, well under the 120% rule. reference 705.12(D)(2) Jeremy All Solar CO,USA ----- Original Message ----- *From:* Garrison Riegel <garri...@solarserviceinc.com> *To:* 'RE-wrenches' <re-wrenches@lists.re-wrenches.org> *Sent:* Wednesday, February 27, 2013 2:15 PM *Subject:* [RE-wrenches] Conductor Sizing for Supply Side Connection Wrenches, On an upcoming job we have a Xantrex XW4548 interconnecting with a 200A service, and I’d very much appreciate some advice if y’all are willing. Since the inverter output OCPD is required to be 60A we are looking at a supply side connection, and I have two questions: 1. Before the point of interconnection the inverter output circuit will first pass through the XW Power Distribution Panel and inverter bypass, which is essentially a 60A breaker. The service disconnect for the supply side connection will also be fused at 60A. Does the 120% rule apply to the conductor between these two OCPDs? Or since this is a supply side connection in accordance with 690.64(A), 690.64(B)(2) will not apply? [this AHJ is on the 2008 NEC] 2. Can anyone recommend a reliable insulation piercing tap connector? Or would you recommend something else entirely for a residential supply side connection? Thanks in advance, Garrison 847-677-0950 Solar Service Inc. ------------------------------ _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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 _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & 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
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