Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters
Hi Bill and wrenches, To clarify, our new Enphase M250 microinverter does not have a grounding terminal. The grounding of the M250 will be provided through the Engage cable. We only have a hole in the lid, in the rare case that a lug will be desired or required by the AHJ, but we do not provide the grounding clip with the microinverter. A grounding terminal can be added to the microinverter. We have an application note on alternate grounding methods for the M250, if needed. On Wed, Sep 18, 2013 at 9:37 AM, Bill Brooks billbroo...@yahoo.com wrote: Dave, Gary, and Charlie, ** ** First, the directions from the manufacturer should be the guide as to whether a GEC is required or not. Just because a GEC terminal is located on the equipment, does not mean that one is required. Case in point—Enphase’s new IG product does not require a GEC, yet it has a grounding terminal for AHJs that might insist on one. This terminal is not intended for a GEC, but it is intended for an extra EGC if the AHJ requires it (LOL on all the abbreviations). ** ** The 2014 NEC makes it very clear that ungrounded PV systems do NOT require an GEC on the dc side and that the ac EGC is sufficient to provide a ground reference for the required dc EGC. ** ** “690.47(B) *Direct-Current Systems.* …*An ac equipment grounding system shall be permitted to be used for equipment grounding of inverters and other equipment and for the ground-fault detection reference for ungrounded PV systems.* ** ** “690.47(C)(3) *Combined Direct-Current Grounding Electrode Conductor and Alternating-Current Equipment* *Grounding Conductor.** An unspliced, or irreversibly spliced, combined grounding conductor shall be run from* *the marked dc grounding electrode conductor connection point along with the ac circuit conductors to the grounding* *busbar in the associated ac equipment. This combined grounding conductor shall be the larger of the sizes specified* *by 250.122 or 250.166 and shall be installed in accordance with 250.64(E).* *For ungrounded systems, this conductor shall be sized in accordance with 250.122 and shall not be required to be larger than the largest ungrounded phase conductor.**”* * * Red letters not Jesus’ words. This is the new language of the 2014 NEC. It is now in print. ** ** The very practical reason that a 6AWG is only required with a single ground rod has to do with the current carrying capacity of a 5/8”, 8’ ground rod in soils of low resistivity—nothing more. ** ** Bill. ** ** ** ** *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Dave Click *Sent:* Wednesday, September 18, 2013 5:38 AM *To:* re-wrenches@lists.re-wrenches.org *Subject:* Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters ** ** I think Gary may be overthinking this. If the micro-inverters have a GEC lug then you'll need to run a GEC. If you run your GEC to a ground rod, then you don't need to use one larger than #6 per 250.166(C). (note also (D) and (E) but they're less useful to you here) * Commentary:* It makes no sense to me why the NEC can require a 0.9in diameter, #600mcm GEC for some systems (not this one) per 250.166(B) and then say oh wait, you installed a single ground rod? Then a #6 is all you need! in 250.166(C). But it certainly makes our lives easier. If the building GE is not a ground rod, you could still run your #6 GEC to that new ground rod, and then bond that rod to the existing electrode using whatever size jumper is required per 250.53 (which I believe would also be a #6). This lets you keep that 300' run as a #6 rather than a #4 or #2 that may be required otherwise. DKC On 2013/9/17 23:56, Gary Willett wrote: Charlie: The answer depends on whether the system (modules and micro-inverters) is grounded or ungrounded. I think you are describing a grounded system, but it's not totally clear based on your issue description. If the micro-inverter is transformer-less the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC. I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters. Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be floating or ungrounded. If the system is ungrounded, a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV
Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters
I think Gary may be overthinking this. If the micro-inverters have a GEC lug then you'll need to run a GEC. If you run your GEC to a ground rod, then you don't need to use one larger than #6 per 250.166(C). (note also (D) and (E) but they're less useful to you here) / Commentary:/ It makes no sense to me why the NEC can require a 0.9in diameter, #600mcm GEC for some systems (not this one) per 250.166(B) and then say oh wait, you installed a single ground rod? Then a #6 is all you need! in 250.166(C). But it certainly makes our lives easier. If the building GE is not a ground rod, you could still run your #6 GEC to that new ground rod, and then bond that rod to the existing electrode using whatever size jumper is required per 250.53 (which I believe would also be a #6). This lets you keep that 300' run as a #6 rather than a #4 or #2 that may be required otherwise. DKC On 2013/9/17 23:56, Gary Willett wrote: Charlie: The answer depends on whether the system (modules and micro-inverters) is grounded or ungrounded. I think you are describing a grounded system, but it's not totally clear based on your issue description. If the micro-inverter is transformer-less the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC. I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters. Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be floating or ungrounded. If the system is ungrounded, a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV-), then your PV system is considered to be grounded. If the system is grounded, the combined DC-GEC and AC-EGC sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table 250.122) and GEC [250.166(B)] sizes will be required. More specifics on the PV module Vmpp and micro-inverter you're dealing with would be helpful. Regards, Gary Willett Icarus Solar On 9/17/13 8:37 PM, Aladdin Solar wrote: We will be installing a 40KW grid-tied PV system that uses PV modules wired in parallel as per the module manufacturer -- so it's a high amperage, low voltage system on the DC side. 2 branches of about 3KW of parallel wired modules each come together onto a DC bus. The DC branch conductors are sized as 2AWG. The inverter system provided by the manufacturer consists of a number of UL1741 single phase microinverters that all are powered off of the low voltage DC bus. So there's a bunch of microinverters in parallel, combined output is single phase power. Those microinverters have a ground lug labeled GEC. You know where this is going... Assuming we are following NEC 690.47(C)(3), we'll be treating this ground as GEC and following all the GEC rules. My understanding is that because the DC conductors within the array are 2AWG (NEC 250.166(B), we will need to connect all 12 branches and 6 DC buses with continuous 2AWG and bring it all the way back 300' to where the AC GEC bond is located. We're getting a lot of pushback from the electrical sub and even some disagreement from the module manufacturer on this--no one's ever seen a grounding conductor of this size being required for this application. Please don't get too bogged down with understanding the low voltage, parallel module spec and the massive number of microinverters involved. What I'm looking for is confirmation that I am properly understanding how the NEC GEC requirements apply, especially to the GEC size. Charlie Pickard NABCEP Certified PV Installation Professional ^(TM) Aladdin Solar, LLC __ Information from ESET NOD32 Antivirus, version of virus signature database 8813 (20130917) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ___ List sponsored by Home Power magazine List Address:RE-wrenches@lists.re-wrenches.org Change email address 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 Change email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive:
Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters
Hi Charlie, I can't help but be intrigued by your setup here. It seems like the complete opposite of where our commercial systems are going with transformerless 1000 V inverters entering the market. Anyway, I'm sure it's an interesting project and there may very well be advantages to the system you're building. I agree with Dave below that you should be okay with a #6 run to a ground rod. Otherwise, your logic for sizing the GEC seems correct. We deal with this similar issue when designing battery backup systems and the GEC can get unwieldy very quickly. I would just point out your sizing logic per 250.166(C) on your plans for the inspector to see. Best, August *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Dave Click *Sent:* Wednesday, September 18, 2013 5:38 AM *To:* re-wrenches@lists.re-wrenches.org *Subject:* Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters I think Gary may be overthinking this. If the micro-inverters have a GEC lug then you'll need to run a GEC. If you run your GEC to a ground rod, then you don't need to use one larger than #6 per 250.166(C). (note also (D) and (E) but they're less useful to you here) * Commentary:* It makes no sense to me why the NEC can require a 0.9in diameter, #600mcm GEC for some systems (not this one) per 250.166(B) and then say oh wait, you installed a single ground rod? Then a #6 is all you need! in 250.166(C). But it certainly makes our lives easier. If the building GE is not a ground rod, you could still run your #6 GEC to that new ground rod, and then bond that rod to the existing electrode using whatever size jumper is required per 250.53 (which I believe would also be a #6). This lets you keep that 300' run as a #6 rather than a #4 or #2 that may be required otherwise. DKC On 2013/9/17 23:56, Gary Willett wrote: Charlie: The answer depends on whether the system (modules and micro-inverters) is grounded or ungrounded. I think you are describing a grounded system, but it's not totally clear based on your issue description. If the micro-inverter is transformer-less the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC. I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters. Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be floating or ungrounded. If the system is ungrounded, a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV-), then your PV system is considered to be grounded. If the system is grounded, the combined DC-GEC and AC-EGC sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table 250.122) and GEC [250.166(B)] sizes will be required. More specifics on the PV module Vmpp and micro-inverter you're dealing with would be helpful. Regards, Gary Willett Icarus Solar On 9/17/13 8:37 PM, Aladdin Solar wrote: We will be installing a 40KW grid-tied PV system that uses PV modules wired in parallel as per the module manufacturer -- so it's a high amperage, low voltage system on the DC side. 2 branches of about 3KW of parallel wired modules each come together onto a DC bus. The DC branch conductors are sized as 2AWG. The inverter system provided by the manufacturer consists of a number of UL1741 single phase microinverters that all are powered off of the low voltage DC bus. So there's a bunch of microinverters in parallel, combined output is single phase power. Those microinverters have a ground lug labeled GEC. You know where this is going... Assuming we are following NEC 690.47(C)(3), we'll be treating this ground as GEC and following all the GEC rules. My understanding is that because the DC conductors within the array are 2AWG (NEC 250.166(B), we will need to connect all 12 branches and 6 DC buses with continuous 2AWG and bring it all the way back 300' to where the AC GEC bond is located. We're getting a lot of pushback from the electrical sub and even some disagreement from the module manufacturer on this--no one's ever seen a grounding conductor of this size being required for this application. Please don't get too bogged down with understanding the low voltage, parallel module spec and the massive number of microinverters involved. What I'm looking for is confirmation that I am properly understanding how the NEC GEC requirements apply, especially to the GEC size. Charlie Pickard NABCEP Certified PV Installation Professional
Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters
I believe this is the tenK solar product being talked about. Jay Peltz power Sent from my iPhone On Sep 18, 2013, at 8:49 AM, August Goers aug...@luminalt.com wrote: Hi Charlie, I can't help but be intrigued by your setup here. It seems like the complete opposite of where our commercial systems are going with transformerless 1000 V inverters entering the market. Anyway, I'm sure it's an interesting project and there may very well be advantages to the system you're building. I agree with Dave below that you should be okay with a #6 run to a ground rod. Otherwise, your logic for sizing the GEC seems correct. We deal with this similar issue when designing battery backup systems and the GEC can get unwieldy very quickly. I would just point out your sizing logic per 250.166(C) on your plans for the inspector to see. Best, August From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Dave Click Sent: Wednesday, September 18, 2013 5:38 AM To: re-wrenches@lists.re-wrenches.org Subject: Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters I think Gary may be overthinking this. If the micro-inverters have a GEC lug then you'll need to run a GEC. If you run your GEC to a ground rod, then you don't need to use one larger than #6 per 250.166(C). (note also (D) and (E) but they're less useful to you here) Commentary: It makes no sense to me why the NEC can require a 0.9in diameter, #600mcm GEC for some systems (not this one) per 250.166(B) and then say oh wait, you installed a single ground rod? Then a #6 is all you need! in 250.166(C). But it certainly makes our lives easier. If the building GE is not a ground rod, you could still run your #6 GEC to that new ground rod, and then bond that rod to the existing electrode using whatever size jumper is required per 250.53 (which I believe would also be a #6). This lets you keep that 300' run as a #6 rather than a #4 or #2 that may be required otherwise. DKC On 2013/9/17 23:56, Gary Willett wrote: Charlie: The answer depends on whether the system (modules and micro-inverters) is grounded or ungrounded. I think you are describing a grounded system, but it's not totally clear based on your issue description. If the micro-inverter is transformer-less the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC. I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters. Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be floating or ungrounded. If the system is ungrounded, a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV-), then your PV system is considered to be grounded. If the system is grounded, the combined DC-GEC and AC-EGC sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table 250.122) and GEC [250.166(B)] sizes will be required. More specifics on the PV module Vmpp and micro-inverter you're dealing with would be helpful. Regards, Gary Willett Icarus Solar On 9/17/13 8:37 PM, Aladdin Solar wrote: We will be installing a 40KW grid-tied PV system that uses PV modules wired in parallel as per the module manufacturer -- so it's a high amperage, low voltage system on the DC side. 2 branches of about 3KW of parallel wired modules each come together onto a DC bus. The DC branch conductors are sized as 2AWG. The inverter system provided by the manufacturer consists of a number of UL1741 single phase microinverters that all are powered off of the low voltage DC bus. So there's a bunch of microinverters in parallel, combined output is single phase power. Those microinverters have a ground lug labeled GEC. You know where this is going... Assuming we are following NEC 690.47(C)(3), we'll be treating this ground as GEC and following all the GEC rules. My understanding is that because the DC conductors within the array are 2AWG (NEC 250.166(B), we will need to connect all 12 branches and 6 DC buses with continuous 2AWG and bring it all the way back 300' to where the AC GEC bond is located. We're getting a lot of pushback from the electrical sub and even some disagreement from the module manufacturer on this--no one's ever seen a grounding conductor of this size being required for this application. Please don't get too bogged down
Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters
Dave, Gary, and Charlie, First, the directions from the manufacturer should be the guide as to whether a GEC is required or not. Just because a GEC terminal is located on the equipment, does not mean that one is required. Case in point-Enphase's new IG product does not require a GEC, yet it has a grounding terminal for AHJs that might insist on one. This terminal is not intended for a GEC, but it is intended for an extra EGC if the AHJ requires it (LOL on all the abbreviations). The 2014 NEC makes it very clear that ungrounded PV systems do NOT require an GEC on the dc side and that the ac EGC is sufficient to provide a ground reference for the required dc EGC. 690.47(B) Direct-Current Systems. .An ac equipment grounding system shall be permitted to be used for equipment grounding of inverters and other equipment and for the ground-fault detection reference for ungrounded PV systems. 690.47(C)(3) Combined Direct-Current Grounding Electrode Conductor and Alternating-Current Equipment Grounding Conductor. An unspliced, or irreversibly spliced, combined grounding conductor shall be run from the marked dc grounding electrode conductor connection point along with the ac circuit conductors to the grounding busbar in the associated ac equipment. This combined grounding conductor shall be the larger of the sizes specified by 250.122 or 250.166 and shall be installed in accordance with 250.64(E). For ungrounded systems, this conductor shall be sized in accordance with 250.122 and shall not be required to be larger than the largest ungrounded phase conductor. Red letters not Jesus' words. This is the new language of the 2014 NEC. It is now in print. The very practical reason that a 6AWG is only required with a single ground rod has to do with the current carrying capacity of a 5/8, 8' ground rod in soils of low resistivity-nothing more. Bill. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Dave Click Sent: Wednesday, September 18, 2013 5:38 AM To: re-wrenches@lists.re-wrenches.org Subject: Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters I think Gary may be overthinking this. If the micro-inverters have a GEC lug then you'll need to run a GEC. If you run your GEC to a ground rod, then you don't need to use one larger than #6 per 250.166(C). (note also (D) and (E) but they're less useful to you here) Commentary: It makes no sense to me why the NEC can require a 0.9in diameter, #600mcm GEC for some systems (not this one) per 250.166(B) and then say oh wait, you installed a single ground rod? Then a #6 is all you need! in 250.166(C). But it certainly makes our lives easier. If the building GE is not a ground rod, you could still run your #6 GEC to that new ground rod, and then bond that rod to the existing electrode using whatever size jumper is required per 250.53 (which I believe would also be a #6). This lets you keep that 300' run as a #6 rather than a #4 or #2 that may be required otherwise. DKC On 2013/9/17 23:56, Gary Willett wrote: Charlie: The answer depends on whether the system (modules and micro-inverters) is grounded or ungrounded. I think you are describing a grounded system, but it's not totally clear based on your issue description. If the micro-inverter is transformer-less the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC. I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters. Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be floating or ungrounded. If the system is ungrounded, a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV-), then your PV system is considered to be grounded. If the system is grounded, the combined DC-GEC and AC-EGC sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table 250.122) and GEC [250.166(B)] sizes will be required. More specifics on the PV module Vmpp and micro-inverter you're dealing with would be helpful. Regards, Gary Willett Icarus Solar On 9/17/13 8:37 PM, Aladdin Solar wrote: We will be installing a 40KW grid-tied PV system that uses PV modules wired in parallel as per the module manufacturer -- so it's a high amperage, low voltage system on the DC side. 2 branches of about 3KW of parallel wired modules each come together onto a DC bus. The DC branch conductors are sized as 2AWG. The inverter system provided
Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters
Nick, Thanks for the clarification-it is a mysterious threaded hole.. Bill. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Nick Soleil Sent: Wednesday, September 18, 2013 10:19 AM To: RE-wrenches Subject: Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters Hi Bill and wrenches, To clarify, our new Enphase M250 microinverter does not have a grounding terminal. The grounding of the M250 will be provided through the Engage cable. We only have a hole in the lid, in the rare case that a lug will be desired or required by the AHJ, but we do not provide the grounding clip with the microinverter. A grounding terminal can be added to the microinverter. We have an application note on alternate grounding methods for the M250, if needed. ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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] GEC sizing for a high amp, low voltage PV system with microinverters
Hi Bill, We wanted to prevent any confusion with inspectors on this topic. So the production units don't even have the threaded PEM nut; just a hole. On Wed, Sep 18, 2013 at 12:42 PM, Bill Brooks billbroo...@yahoo.com wrote: Nick, ** ** Thanks for the clarification—it is a mysterious threaded hole…. ** ** Bill. ** ** *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Nick Soleil *Sent:* Wednesday, September 18, 2013 10:19 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters ** ** Hi Bill and wrenches, To clarify, our new Enphase M250 microinverter does not have a grounding terminal. The grounding of the M250 will be provided through the Engage cable. We only have a hole in the lid, in the rare case that a lug will be desired or required by the AHJ, but we do not provide the grounding clip with the microinverter. A grounding terminal can be added to the microinverter. We have an application note on alternate grounding methods for the M250, if needed. ** ** ** ** ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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 -- Cordially, *Nick Soleil* *Field Applications Engineer * *Enphase Energy* Mobile: (707) 321-2937 ** *Enphase Commercial Solar.* *Limitless.*http://www.enphase.com/commercial?utm_source=emailutm_medium=sigutm_campaign=Comm2012 * *http://www.enphase.com/commercial?utm_source=emailutm_medium=sigutm_campaign=Comm2012 1420 North McDowell Petaluma, CA 94954 www.enphase.com http://www.enphaseenergy.com/ P: (707) 763-4784 x7267 F: (707) 763-0784 E: nsol...@enphaseenergy.com [image: nabcep logo] Certified Solar PV Installer #03262011-300 “Don’t get me wrong: I love nuclear energy! It’s just that I prefer fusion to fission. And it just so happens that there’s an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it’s wireless! .” - William McDonough This email message is for the sole use of the intended recipient(s) and may contain confidential and/or privileged information. If you are not an intended recipient, you may not review, use, copy, disclose or distribute this message. If you received this message in error, please contact the sender by reply email and destroy all copies of the original message. image002.jpg___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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] GEC sizing for a high amp, low voltage PV system with microinverters
Thanks Brian. That helps. Charlie Pickard NABCEP Certified PV Installation Professional ™ Aladdin Solar,LLC - Original Message - From: Brian Mehalic To: Aladdin Solar ; RE-wrenches Sent: Wednesday, September 18, 2013 4:17 PM Subject: Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters Sole connection indicates that a GEC is connected to only one type of grounding electrode. This term is easily mis- understood. For example, a GEC can be connected to more than one grounding electrode—say, two ground rods—and still be considered to have a sole connection. Similarly, multiple GECs connected to the same grounding electrode are each considered to have a sole connection. When GECs have a sole connection, their maximum size is limited per NEC Sections 250.66 for an ac system and 250.166 for a dc system. The 2014 NEC adds some clarification on this. Brian Mehalic NABCEP Certified Solar PV Installation Professional™ R031508-59 IREC ISPQ Certified Affiliated Instructor/PV US-0132 PV Curriculum Developer and Instructor Solar Energy International http://www.solarenergy.org On Wed, Sep 18, 2013 at 4:52 PM, Aladdin Solar cpick...@aladdinsolar.com wrote: Yes, Jay, this is a TenKSolar system -- they certainly do have a habit of taking the 'thinking outside the box' approach! The microinverter manufacturer states in their installation manual, Connect the grounding electrode conductor to the microinverter ground clamp so it's quite clear we are dealing with GEC rules. Thanks for all your comments and the reminder of the NEC 250.166(C) exception which I hadn't really connected with before. I'm having difficulty understanding what the requirement in that paragraph actually means. When it states that portion of the grounding electrode conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6AWG... -- what does that portion and sole connection mean? If we have a number of GEC branches from that are irreversably spliced to a single 6AWG conductor bonded to the grounding electrode, do those various GECs affect the that portion and sole connection at all? Charlie Pickard NABCEP Certified PV Installation Professional ™ Aladdin Solar, LLC - Original Message - From: Bill Brooks To: 'RE-wrenches' Sent: Wednesday, September 18, 2013 2:42 PM Subject: Re: [RE-wrenches] GEC sizing for a high amp,low voltage PV system with microinverters Nick, Thanks for the clarification—it is a mysterious threaded hole…. Bill. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Nick Soleil Sent: Wednesday, September 18, 2013 10:19 AM To: RE-wrenches Subject: Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters Hi Bill and wrenches, To clarify, our new Enphase M250 microinverter does not have a grounding terminal. The grounding of the M250 will be provided through the Engage cable. We only have a hole in the lid, in the rare case that a lug will be desired or required by the AHJ, but we do not provide the grounding clip with the microinverter. A grounding terminal can be added to the microinverter. We have an application note on alternate grounding methods for the M250, if needed. __ Information from ESET NOD32 Antivirus, version of virus signature database 8815 (20130918) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.com -- ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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 __ Information from ESET NOD32 Antivirus, version of virus signature database 8815 (20130918) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __ Information from ESET NOD32 Antivirus, version of virus signature database 8817 (20130918) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org
Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters
Charlie: The answer depends on whether the "system" (modules and micro-inverters) is "grounded" or "ungrounded". I think you are describing a "grounded" system, but it's not totally clear based on your issue description. If the micro-inverter is "transformer-less" the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC. I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters. Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be "floating" or "ungrounded". If the system is "ungrounded", a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV-), then your PV system is considered to be "grounded". If the system is "grounded", the combined DC-GEC and AC-EGC sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table 250.122) and GEC [250.166(B)] sizes will be required. More specifics on the PV module Vmpp and micro-inverter you're dealing with would be helpful. Regards, Gary Willett Icarus Solar On 9/17/13 8:37 PM, Aladdin Solar wrote: We will be installing a 40KW grid-tied PV system that uses PV modules wired in parallel as per the module manufacturer-- so it's a high amperage, low voltage system on the DC side. 2 branches of about 3KW of parallel wired modules each come together onto a DC bus. The DC branch conductors are sized as 2AWG. The inverter system provided by the manufacturer consists of a number of UL1741 single phase microinverters that all are powered off of the low voltage DC bus. So there's a bunch of microinverters in parallel, combined output is single phase power. Those microinverters have a ground lug labeled "GEC". You know where this is going... Assuming we are following NEC 690.47(C)(3), we'll betreating this ground as GEC and following all the GEC rules. My understanding is that because the DC conductors within the array are 2AWG (NEC 250.166(B), we will need to connect all 12 branches and 6 DC buses with continuous 2AWG and bring it all the way back 300' to where the AC GEC bond is located. We're getting a lot of pushback from the electrical sub and even some disagreement from the module manufacturer on this--no one's ever seen a grounding conductor of this size being required for this application. Please don't get too bogged down with understanding the low voltage, parallel module spec and the massive number of microinverters involved. What I'm looking for is confirmation that I am properly understandinghow theNEC GEC requirements apply, especially to the GEC size. Charlie Pickard NABCEP Certified PV Installation Professional Aladdin Solar, LLC __ Information from ESET NOD32 Antivirus, version of virus signature database 8813 (20130917) __ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address 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 Change email address 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
