System grounding requirements. -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Mark Frye Sent: Friday, March 04, 2011 7:51 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] grounding the Enphase inverter
The interesting thing to me is the underlying assumption in the Code that a GEC is requried for grid-tied inverters at all. Why isn't EG sufficient for function and safety. Which of the following common electrical equipment has the same requirement: UPS Motors with regenerative energy disipators DC power supplies Standby generators ?? 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 Bill Brooks Sent: Thursday, March 03, 2011 10:48 PM To: 'RE-wrenches' Subject: Re: [RE-wrenches] grounding the Enphase inverter All, While there is ambiguity in the 2008 NEC in 690.47(C) on the requirements for system grounding of PV systems, the 2011 NEC in 690.47(C) clarifies the intent. While an application note from Enphase may state that WEEBs can be used as part of the grounding electrode system, I disagree with this concept and do not believe it meets the requirements or intent of the NEC as clarified in the 2011 NEC. The problem with a grounded PV inverter is that it requires a grounding electrode conductor (GEC) from the grounding point (on the inverter) to the grounding electrode. The 2008 and 2011 NEC allows for that connection to be terminated at the grounding bar in the service panel supplying the micro-inverters. There is no problem with using the WEEB to bond the rails to the modules and then to the Enphase Micro-inverter. From the micro-inverter, a bare 6AWG could be run to pick up each micro-inveter in each row of micro-inverters with splices made to a single bare 6AWG made with irreversible splices. At the rooftop junction box, the GEC could be irreversibly spliced to an 8AWG green insulated conductor to run unbroken to the grounding busbar in the service equipment. While this may not be in agreement with the Enphase application note, I believe it meets the intent and letter of the NEC as clarified in the 2011 NEC 690.47(C). While using the WEEBs in the GEC circuit may not cause a life or death issue, it is absolutely open to being questioned by the electrical inspector. If the electrical inspector decides it is wrong--it is wrong. If you or the field inspector appeals to me or an expert like John Wiles, we will state what I have stated above. Then you would have to remove all the modules, throw away the WEEBs, put in new WEEBs with the new bare copper 6AWG and reinstall the modules--it just ain't worth it. 690.47(D) was removed from the 2011 NEC because it was primarily for lightning protection (not a safety issue according to the NEC) and was ambiguously worded with respect to residential rooftop PV systems. If the local jurisdiction requires the additional electrode, install a j-box at the point near ground-level where the conduit transitions from vertical to horizontal and install an irreversibly spliced bare 6AWG to run from the j-box to a ground rod below the j-box--mildly painful, but very doable. Bill. Bill Brooks, PE Principal Brooks Engineering 873 Kells Circle Vacaville, CA 95688 707-332-0761 (office and mobile) 707-451-7739 (fax) b...@brooksolar.com (email) www.brooksolar.com (web) _______________________________________________ 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 _______________________________________________ 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
