Mark, Thank you for pointing me to 690.43 NEC 2008. I'm embarrassed to confess I was unaware of the change there from 2005.
This weekend, I've spent more time than I care to admit, trying to discover and understand the rationale for that change. In this, I will admit, I was unsuccessful. Failing to understand, one is left with the choice to either follow the code, or continue with what seems to be a safer, and previously acceptable practice. According to John Wiles, the code making panel for 2008 Article 690 was disbanded by the NFPA because it, "violated NEC code developement procedures and because of other issues." Doesn't leave one with much confidence in their work. I lived in Western Washington 1977 to 1980 and actually missed the frequent summer thunderstorms I'd grown up with in Pennsylvania. Unfortunately, they are often destructive, if not deadly. Here in VT /NH I have heard of phones blasted off the wall, large blue sparks leaping from wall receptacles and a Honda generator's remote starting unit. A woman reported her long hair stood on end as a storm approached her pole mount array. My son has burn marks on the front of his television where he and a friend watched flames leap from it during a nearby strike. I have followed up on other installers work, where inverters, charge controllers and other equipment was damaged or destroyed. The internet is replete with spectacular accounts and photographs. I do think arrays should have a low inpedance ground, local to the array and exterior to to any structure, particularly a residence. It is frustrating to still be debating the best way to deal with this important issue. Dick Ratico Solarwind Electric Bradford, VT --- You wrote: Dick, Kudos for the contributions to the magazine. I do hope as John W. speculates that this will all be sorted out in NEC 2011. In the meantime, while I can see the validity of your method, I don't think it is well supported by NEC 2008. Specifally at 690.43 (which would overide the more general allowances of 250) that requires the EGC for the PV array to be contained within the same raceway as the PV circuit conductors when they leave the vicinity of the array. Unfortunately, the ambiguity of the Code is causing everyone to come up with their own creative solutions, so long as they can sell them to the AJH, if any. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 www.berkeleysolar.com -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Richard L Ratico Sent: Friday, June 05, 2009 6:56 PM To: re-wrenches@lists.re-wrenches.org Subject: Re: [RE-wrenches] 690.47D (revisited) Kelly, I always install a grounding electrode at the array. I always run a continuous (not spliced), properly sized, or oversize (usually #4), bare, copper conductor from the array modules and frame, to that electrode, then continue it, direct buried, to all of the other grounding electrodes in the system. I DO NOT run a separate equipment grounding conductor (EGC) with the array circuit conductors, for the reason you mention. I don't want to create a ground loop. I also want to keep any energy from lightning away from the circuit conductors. Here in Vermont, we get our share of lightning and I've seen way too much equipment that's been fried. The NEC, in article 250 permits the EGC, IN DC CIRCUITS ONLY, to be run SEPARATELY from the DC circuit conductors. In the method above, the direct buried, bare conductor serves as BOTH the EGC and the GEC for the array. In the premier issue of Solar Pro Magazine, <http://solarprofessional.com/article/?file=SP1_1_pg28_3Phase> Bill Brooks, John Wiles and I took turns trying to make sense of 690.47. I'm not sure we succeeded. :-) There are no residential inspections in VT. Hope this helps. Dick --- end of quote --- _______________________________________________ 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
