Thanks Kelly, I haven't gotten the handbook, but I think I am getting the picture.
How nice of the handbook to let us know that the new GE and GEC that "shall be installed" according to 690.47D is nothing more than an "optional supplementary ground electrode". And furher, if you do choose to take the option of installing it, in order to have the best lightning protection, you don't have to bond it to the exisiting GE system. How easy to now disregard 250.106 which says that 'The lightning protection system ground terminals shall be bonded to the building or structure grounding electrode system". Considering the inherant problems of 690.47D, I can certainly understand any AJH trying to avoid this issue of the creation of a whole new class of GE's who's use falls completely outside the basic definitions of 250 III 250.50, "All grounding electrodes.....shall be bonded together to form the grounding electrode system." MPF Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 www.berkeleysolar.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Kelly Keilwitz, Whidbey Sun & Wind Sent: Friday, June 05, 2009 12:11 PM To: RE Wrenches listserve Subject: Re: [RE-wrenches] 690.47D (revisited) Mark, I don't think that the 690.47D "PV GE" is part of the premises AC & DC ground electrode system. IMO, in order to function to properly as ³enhanced protection from lightning induced surges² as described in the 690.47(D) section note in the 2008 NEC Handbook, the ³optional supplementary grounding electrode² should not be connected to the premises system AC and DC grounding electrodes, as shown in Exhibit 690.6 of the Handbook. If an additional #8 (per 250.166) is bonded to the premises AC/DC system GE, it's path will be parallel with, and redundant to, the existing EGC. This could set up the potential for an inductive ground loop, which might cause more damage to the system during a lightning strike than it would prevent. If the ³additional electrode for array grounding² (PV GE) of 690.47D is not required, then the PV GEC of that section should not be required. Of course, these opinions are academic. What I really want to know is what the AHJ's think! Any of you have to deal with this, yet? Thanks, -Kelly _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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
