All,
The 2011 NEC reference for stand-alone systems is 705.12(D)(2) Exception: Exception: Where the photovoltaic system has an energy storage device to allow stand-alone operation of loads, the value used in the calculation of bus or conductor loading shall be 125 percent of the rated utility-interactive current from the inverter instead of the rating of the overcurrent device between the inverter and the bus or conductor. The 2014 NEC made this the rules of the road for all inverter output circuits connected to other sources. Bill. From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Howie Michaelson Sent: Friday, August 12, 2016 8:39 AM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] 120% rule for hybrid inverters Mark, I read that section as stating that both must be true, which I would take to mean if one is using a 20 amp breaker to protect the output from a 3 kW inverter, you need to count it as 20 amps toward the 120% rule, not the 15.63 amps the 125% calculation would infer. I know that 2014 was changed to allow for larger breakers to feed hybrid inverters, but I can't recite the code that allows that (unless I am misreading the intent of the section you quoted). Can you clarify this for me? Thanks, Howie Howie Michaelson NABCEP Certified Solar PV Installer™ Sun Catcher, LLC Renewable Energy Systems Sales and Service VT Solar Electric Incentive Partner 802-272-0004 On Fri, Aug 12, 2016 at 9:39 AM, Mark Westbrock <westbr...@positiveenergysolar.com <mailto:westbr...@positiveenergysolar.com> > wrote: Hi Mac, The wording changed because in the 2011 NEC 705.12(D) you had to use the size of your backfeed breaker in calculating the busbar loading, but in 2014, 705.12(D)(2)(3)(b) now says "125 percent of the inverter output circuit current and the rating of the OCPD protecting the busbar shall not exceed 120%". So, the 2014 wording basically allows all inverters to follow the exception that used to be there for hybrid inverters. I hope that helps. Cheers, Mark ---- Mark Westbrock| VP, Branch Manager | Employee Owner NABCEP™ Certified PV Installation Professional NABCEP™ Certified Technical Sales Professional NM EE98J Licensed Electrician 510 S. Main St., Las Cruces, NM 88001 cell 575.640.2432 <tel:575.640.2432> | office 575.524.2030 <tel:575.524.2030> <mailto:your.em...@positiveenergysolar.com> m...@positiveenergysolar.com <http://www.positiveenergysolar.com/> www.PositiveEnergySolar.com <http://www.positiveenergysolar.com> On Fri, Aug 12, 2016 at 7:26 AM, Mac Lewis <maclew...@gmail.com <mailto:maclew...@gmail.com> > wrote: Hello wrenches, I am looking for the exception to the 120% rule in the 2014 code that allowed for compliance to the 120% rule to be based on the utility-interactive current as opposed to the backfeed breaker size for hybrid inverter. I hope this still exists, but I'm having a hard time finding it in the 2014 code. In 2011 it was 705.12(D)2 Exception. That was nice clear language that all inspectors accepted, I'm hoping the same exists for the 2014 code. Thanks in advance code experts -- Mac Lewis "Yo solo sé que no sé nada." -Sócrates _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org <mailto:RE-wrenches@lists.re-wrenches.org> Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm <http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org <http://www.members.re-wrenches.org> _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org <mailto:RE-wrenches@lists.re-wrenches.org> Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm <http://www.re-wrenches.org/etiquette.htm> Check out or update participant bios: www.members.re-wrenches.org <http://www.members.re-wrenches.org>
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