Re: [RE-wrenches] EGC vs GEC, separately derived system
We typically run a #6 combined EGC/GEC on all residential systems just to keep it simple. The cost difference is typically negligible. We use irreversible C-crimps to combine the wires in a roof mounted junction box. *Jason Szumlanski* *Fafco Solar* On Wed, Nov 28, 2012 at 10:56 PM, mac Lewis maclew...@gmail.com wrote: Hello wrenches, What constitutes a separately derived system? Would you consider a breaker tied enphase system a separately-derived system? Suddenly, inspectors in our AHJ are considering all PV systems separately derived systems and thus requiring applying GEC sizing (as opposed to EGC sizing) from the inverter(s) to the tie in point. This does not jive with my understanding. Would like to hear other thoughts about this. Here is the definition of a separately derived system as per 2008 NEC Article 100 Definitions: *Separately Derived System*: *A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.* For your enphase systems do you size your ground from roof to the breaker panel as an EGC or a GEC? Thanks in advance for your thoughts. -- Mac Lewis * Yo solo sé que no sé nada. -Sócrates * ___ 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
Re: [RE-wrenches] EGC vs GEC, separately derived system
The separately derived issue aside, enphase inverters have an internal DC system ground and a marked point from which a DC GEC must be installed. Typically grounding is being done in the manner stated in 690.47(C)(3) - a single conductor as both the DC GEC and EGC, meaning it has to be the larger of the two sizes required; for most enphase systems, based on the interconnection breaker size, the minimum EGC would typically be #12 (Table 250.122), but the minimum size for a DC EGC is #8. A #6 may be preferable under the array due to interpretations about the conductor being subject to damage. Brian Mehalic NABCEP Certified Solar PV Installer™ R031508-59 IREC ISPQ Certified Affiliated Instructor/PV US-0132 PV Curriculum Developer and Instructor Solar Energy International http://www.solarenergy.org On Wed, Nov 28, 2012 at 10:56 PM, mac Lewis maclew...@gmail.com wrote: Hello wrenches, What constitutes a separately derived system? Would you consider a breaker tied enphase system a separately-derived system? Suddenly, inspectors in our AHJ are considering all PV systems separately derived systems and thus requiring applying GEC sizing (as opposed to EGC sizing) from the inverter(s) to the tie in point. This does not jive with my understanding. Would like to hear other thoughts about this. Here is the definition of a separately derived system as per 2008 NEC Article 100 Definitions: *Separately Derived System*: *A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.* For your enphase systems do you size your ground from roof to the breaker panel as an EGC or a GEC? Thanks in advance for your thoughts. -- Mac Lewis * Yo solo sé que no sé nada. -Sócrates * ___ 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
Re: [RE-wrenches] EGC vs GEC, separately derived system
Hi Mac, I think the answer to your separately derived system question is in the code snippet you pasted in below. Clearly, your Enphase grid tied system has a direct electrical connection to the utility. A generator system that runs while the grid is down would be an example of a separately derived system since it will always have a transfer switch to separate the electrical connections. In other words, the grid tied solar system is designed to work in unison with the grid while a separately must only operate independently. At least that is how I try to explain it to inspectors around here. I believe Brian Mehalic's email clearly speaks to why you still need a GEC for the Enphase based system. Incidentally, we're starting to work with listed ACPV modules and transformerless (non-isolated) inverters which don't have a DC GEC requirement. This is a major benefit to help reduce installed costs. 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 *mac Lewis *Sent:* Wednesday, November 28, 2012 7:56 PM *To:* RE-wrenches *Subject:* [RE-wrenches] EGC vs GEC, separately derived system Hello wrenches, What constitutes a separately derived system? Would you consider a breaker tied enphase system a separately-derived system? Suddenly, inspectors in our AHJ are considering all PV systems separately derived systems and thus requiring applying GEC sizing (as opposed to EGC sizing) from the inverter(s) to the tie in point. This does not jive with my understanding. Would like to hear other thoughts about this. Here is the definition of a separately derived system as per 2008 NEC Article 100 Definitions: *Separately Derived System*: *A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.* For your enphase systems do you size your ground from roof to the breaker panel as an EGC or a GEC? Thanks in advance for your thoughts. -- Mac Lewis** Yo solo sé que no sé nada. *-Sócrates*** ___ 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
[RE-wrenches] EGC vs GEC, separately derived system
Hello wrenches, What constitutes a separately derived system? Would you consider a breaker tied enphase system a separately-derived system? Suddenly, inspectors in our AHJ are considering all PV systems separately derived systems and thus requiring applying GEC sizing (as opposed to EGC sizing) from the inverter(s) to the tie in point. This does not jive with my understanding. Would like to hear other thoughts about this. Here is the definition of a separately derived system as per 2008 NEC Article 100 Definitions: *Separately Derived System*: *A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.* For your enphase systems do you size your ground from roof to the breaker panel as an EGC or a GEC? Thanks in advance for your thoughts. -- Mac Lewis * Yo solo sé que no sé nada. -Sócrates * ___ 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
