Re: [RE-wrenches] Finding ground faults
Mike: Is there such a tool as a DC clamp-on that can reliably measure 10 mA? My experience is any clamp meter is unreliable below 5A. William At 10:09 PM 5/23/2012, Mike Sullivan wrote: Hi Bob, Sorry if I am duplicating any of the replies you've already received regarding the possible ground fault. I think the best way to determine whether GFDI is tripping on 1 A ground current or 80 A circuit current is to use a sensitive DC clamp-on to check the current on your system ground under normal operation. If it is more than about 10 mA when things are dry, you probably do have a ground fault issue to resolve. Assuming that's true, I recommend that you buy, borrow or rent a megohm tester (like those by Megger) to check out your circuit wiring resistance. Once you fully isolate your strings at the combiner box, you can quickly zero in on where the fault lies -- just divide and conquer. You may need to wet down the array and wiring to make the fault more detectable. Often, the fault will be in wiring that was damaged when pulled from a splice or combiner box into conduit, esp. if there's no bushing on the conduit terminal adapter. A word of warning -- if you have more than one ground fault, some parts of your equipment grounding system will be carrying current, which may be sizable. Use precautions when disconnecting any wiring or grounds. A clamp-on is really useful here... Hope that helps! Cheers, Mike Sullivan Wrenches: ? Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings?not that 75-85 volts per string is all that low). ? We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers.? The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. ? Up until this week the system has seen several weeks of awesome power production.? Yesterday, the rains came and the GFDI breaker tripped.? Every time it rains, the little green breaker on the GFDI trips off. ?That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. ? It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes.? This would mean removing the central modules to access the pass-through boxes. ? Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes.? So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules.? I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. ? How best (and safely) to track down where the ground fault is occurring?? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. ? Bob Clark SolarWind Energy Systems, LLC ___ 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 No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.455 / Virus Database: 271.1.1/5018 - Release Date: 05/23/12 18:41:00 Miller Solar Voice :805-438-5600 email: will...@millersolar.com http://millersolar.com License No. C-10-773985 ___ 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] Finding ground faults
Yes. Look for 4-20mA loop clamp on meters. Fluke 77x series is an example: http://www.fluke.com/Fluke/usen/Clamp-Meters/Fluke-771-Milliamp-Process-Clamp-Meter.htm?PID=69415 0 to 100mA with 1% accuracy worst case over the whole range. -James Jarvis APRS World, LLC On 05/24/2012 12:49 AM, William Miller wrote: Mike: Is there such a tool as a DC clamp-on that can reliably measure 10 mA? My experience is any clamp meter is unreliable below 5A. ___ 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] Finding ground faults
Here's the Paul Mync / John Berdner article from SolarPro 2.5: http://solarprofessional.com/article/?file=SP2_5_pg60_Mync -David Brearley... er... Click On 2012/5/22 22:36, Bob Clark wrote: Wrenches: Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings—not that 75-85 volts per string is all that low). We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers. The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. Up until this week the system has seen several weeks of awesome power production. Yesterday, the rains came and the GFDI breaker tripped. Every time it rains, the little green breaker on the GFDI trips off. That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes. This would mean removing the central modules to access the pass-through boxes. Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes. So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules. I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. How best (and safely) to track down where the ground fault is occurring? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. *Bob Clark* */SolarWind Energy Systems, LLC/* ___ 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] Finding ground faults
Steve, It would be appropriate for the GFDI to have 80-amp rated contacts that do not have an over-current trip mechanism. IMHO, the fact that they can trip on over-current and unnecessarily interrupt the dc system bond is a serious design flaw. Kent Osterberg Blue Mountain Solar, Inc. www.bluemountainsolar.com On 5/23/2012 9:27 AM, Steve Higgins wrote: Bob, Be careful with that GFDI... It's most likely wired on the output of the controllers, on the battery side. This can trip if a ground fault is occurring, or if you are exceeding 80 amps of current. With 8, 3 module strings, an edge of cloud event you could have the 80amp portion of that breaker tripping rather than the GFDI. Steve Higgins Sales Application Engineering Mgr Direct 360-618-4313 Outback Power Technologies 5917 195th Street NE Arlington, Washington 98223 *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Bob Clark *Sent:* Tuesday, May 22, 2012 7:37 PM *To:* re-wrenches@lists.re-wrenches.org *Subject:* [RE-wrenches] Finding ground faults Wrenches: Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings---not that 75-85 volts per string is all that low). We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers. The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. Up until this week the system has seen several weeks of awesome power production. Yesterday, the rains came and the GFDI breaker tripped. Every time it rains, the little green breaker on the GFDI trips off. That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes. This would mean removing the central modules to access the pass-through boxes. Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes. So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules. I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. How best (and safely) to track down where the ground fault is occurring? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. *Bob Clark* */SolarWind Energy Systems, LLC/* ___ 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] Finding ground faults
Steve: IMHO, a brilliant suggestion. William Miller At 11:19 AM 5/23/2012, you wrote: Steve, It would be appropriate for the GFDI to have 80-amp rated contacts that do not have an over-current trip mechanism. IMHO, the fact that they can trip on over-current and unnecessarily interrupt the dc system bond is a serious design flaw. Kent Osterberg Blue Mountain Solar, Inc. http://www.bluemountainsolar.comwww.bluemountainsolar.com ___ 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] Finding ground faults
From what I understand, future controllers from Outback Power will incorporate the Ground Fault detection into the controller. Steve Higgins Sales Application Engineering Mgr Direct 360-618-4313 Outback Power Technologies 5917 195th Street NE Arlington, Washington 98223 From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller Sent: Wednesday, May 23, 2012 11:22 AM To: RE-wrenches Subject: Re: [RE-wrenches] Finding ground faults Steve: IMHO, a brilliant suggestion. William Miller At 11:19 AM 5/23/2012, you wrote: Steve, It would be appropriate for the GFDI to have 80-amp rated contacts that do not have an over-current trip mechanism. IMHO, the fact that they can trip on over-current and unnecessarily interrupt the dc system bond is a serious design flaw. Kent Osterberg Blue Mountain Solar, Inc. www.bluemountainsolar.comhttp://www.bluemountainsolar.com ___ 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] Finding ground faults
Bob I had a tough find one time, when it rained I would have GF when it would dry out no GF I turned off main DC disconnect, I turned off each circuit breakers for the strings, I opened the grounded conductor of the strings, I connected my Megger at 500 volts I think It might have been maybe 1000 volts, after the fault cleared, the megger found one string that was bad and I located the problem in a J box From: Steve Higgins shigg...@outbackpower.com To: RE-wrenches re-wrenches@lists.re-wrenches.org Sent: Wednesday, May 23, 2012 11:27 AM Subject: Re: [RE-wrenches] Finding ground faults Bob, Be careful with that GFDI... It's most likely wired on the output of the controllers, on the battery side. This can trip if a ground fault is occurring, or if you are exceeding 80 amps of current. With 8, 3 module strings, an edge of cloud event you could have the 80amp portion of that breaker tripping rather than the GFDI. Steve Higgins Sales Application Engineering Mgr Direct 360-618-4313 Outback Power Technologies 5917 195th Street NE Arlington, Washington 98223 From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Bob Clark Sent: Tuesday, May 22, 2012 7:37 PM To: re-wrenches@lists.re-wrenches.org Subject: [RE-wrenches] Finding ground faults Wrenches: Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings—not that 75-85 volts per string is all that low). We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers. The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. Up until this week the system has seen several weeks of awesome power production. Yesterday, the rains came and the GFDI breaker tripped. Every time it rains, the little green breaker on the GFDI trips off. That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes. This would mean removing the central modules to access the pass-through boxes. Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes. So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules. I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. How best (and safely) to track down where the ground fault is occurring? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. Bob Clark SolarWind Energy Systems, LLC ___ 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] Finding ground faults
I sure do not like the way the X brand installed their charge controller, Also the code says that all strings must open if one string is faulted. your breaker does this up to 4 strings. DT From: Steve Higgins shigg...@outbackpower.com To: RE-wrenches re-wrenches@lists.re-wrenches.org Sent: Wednesday, May 23, 2012 2:18 PM Subject: Re: [RE-wrenches] Finding ground faults From what I understand, future controllers from Outback Power will incorporate the Ground Fault detection into the controller. Steve Higgins Sales Application Engineering Mgr Direct 360-618-4313 Outback Power Technologies 5917 195th Street NE Arlington, Washington 98223 From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller Sent: Wednesday, May 23, 2012 11:22 AM To: RE-wrenches Subject: Re: [RE-wrenches] Finding ground faults Steve: IMHO, a brilliant suggestion. William Miller At 11:19 AM 5/23/2012, you wrote: Steve, It would be appropriate for the GFDI to have 80-amp rated contacts that do not have an over-current trip mechanism. IMHO, the fact that they can trip on over-current and unnecessarily interrupt the dc system bond is a serious design flaw. Kent Osterberg Blue Mountain Solar, Inc. www.bluemountainsolar.com ___ 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] Finding ground faults
On 5/23/2012 4:44 PM, Darryl Thayer wrote: I sure do not like the way the X brand installed their charge controller, Also the code says that all strings must open if one string is faulted. your breaker does this up to 4 strings. DT I think that this is the pertinent part of the code regarding this... In part... 31.1 Inverters or charge controllers with direct photovoltaic inputs from a grounded photovoltaic array or arrays shall be provided with a ground-fault detector/interrupter (GFDI). The GFDI shall be capable of detecting a ground fault, providing an indication of the fault, interrupting the flow of fault current, and either isolating the faulted array section or disabling the inverter to cease the export of power. This may very well change in the 2014 NEC from what I understand. boB *From:* Steve Higgins shigg...@outbackpower.com *To:* RE-wrenches re-wrenches@lists.re-wrenches.org *Sent:* Wednesday, May 23, 2012 2:18 PM *Subject:* Re: [RE-wrenches] Finding ground faults From what I understand, future controllers from Outback Power will incorporate the Ground Fault detection into the controller. Steve Higgins Sales Application Engineering Mgr Direct 360-618-4313 Outback Power Technologies 5917 195th Street NE Arlington, Washington 98223 *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *William Miller *Sent:* Wednesday, May 23, 2012 11:22 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] Finding ground faults Steve: IMHO, a brilliant suggestion. William Miller At 11:19 AM 5/23/2012, you wrote: Steve, It would be appropriate for the GFDI to have 80-amp rated contacts that do not have an over-current trip mechanism. IMHO, the fact that they can trip on over-current and unnecessarily interrupt the dc system bond is a serious design flaw. Kent Osterberg Blue Mountain Solar, Inc. www.bluemountainsolar.com http://www.bluemountainsolar.com ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org mailto: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 ___ 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] Finding ground faults
Ooops !! Sorry about that one !!That was from 1741... Still applicable of course but NOT NEC. That was applicable from 2007 though. boB On 5/23/2012 6:34 PM, b...@midnitesolar.com wrote: On 5/23/2012 4:44 PM, Darryl Thayer wrote: I sure do not like the way the X brand installed their charge controller, Also the code says that all strings must open if one string is faulted. your breaker does this up to 4 strings. DT I think that this is the pertinent part of the code regarding this... In part... 31.1 Inverters or charge controllers with direct photovoltaic inputs from a grounded photovoltaic array or arrays shall be provided with a ground-fault detector/interrupter (GFDI). The GFDI shall be capable of detecting a ground fault, providing an indication of the fault, interrupting the flow of fault current, and either isolating the faulted array section or disabling the inverter to cease the export of power. This may very well change in the 2014 NEC from what I understand. boB *From:* Steve Higgins shigg...@outbackpower.com *To:* RE-wrenches re-wrenches@lists.re-wrenches.org *Sent:* Wednesday, May 23, 2012 2:18 PM *Subject:* Re: [RE-wrenches] Finding ground faults From what I understand, future controllers from Outback Power will incorporate the Ground Fault detection into the controller. Steve Higgins Sales Application Engineering Mgr Direct 360-618-4313 Outback Power Technologies 5917 195th Street NE Arlington, Washington 98223 *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *William Miller *Sent:* Wednesday, May 23, 2012 11:22 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] Finding ground faults Steve: IMHO, a brilliant suggestion. William Miller At 11:19 AM 5/23/2012, you wrote: Steve, It would be appropriate for the GFDI to have 80-amp rated contacts that do not have an over-current trip mechanism. IMHO, the fact that they can trip on over-current and unnecessarily interrupt the dc system bond is a serious design flaw. Kent Osterberg Blue Mountain Solar, Inc. www.bluemountainsolar.com http://www.bluemountainsolar.com ___ 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] Finding ground faults
Hi Bob, Sorry if I am duplicating any of the replies you've already received regarding the possible ground fault. I think the best way to determine whether GFDI is tripping on 1 A ground current or 80 A circuit current is to use a sensitive DC clamp-on to check the current on your system ground under normal operation. If it is more than about 10 mA when things are dry, you probably do have a ground fault issue to resolve. Assuming that's true, I recommend that you buy, borrow or rent a megohm tester (like those by Megger) to check out your circuit wiring resistance. Once you fully isolate your strings at the combiner box, you can quickly zero in on where the fault lies -- just divide and conquer. You may need to wet down the array and wiring to make the fault more detectable. Often, the fault will be in wiring that was damaged when pulled from a splice or combiner box into conduit, esp. if there's no bushing on the conduit terminal adapter. A word of warning -- if you have more than one ground fault, some parts of your equipment grounding system will be carrying current, which may be sizable. Use precautions when disconnecting any wiring or grounds. A clamp-on is really useful here... Hope that helps! Cheers, Mike Sullivan Wrenches: ? Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings?not that 75-85 volts per string is all that low). ? We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers.? The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. ? Up until this week the system has seen several weeks of awesome power production.? Yesterday, the rains came and the GFDI breaker tripped.? Every time it rains, the little green breaker on the GFDI trips off. ?That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. ? It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes.? This would mean removing the central modules to access the pass-through boxes. ? Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes.? So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules.? I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. ? How best (and safely) to track down where the ground fault is occurring?? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. ? Bob Clark SolarWind Energy Systems, LLC ___ 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] Finding ground faults
Wrenches: Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings-not that 75-85 volts per string is all that low). We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers. The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. Up until this week the system has seen several weeks of awesome power production. Yesterday, the rains came and the GFDI breaker tripped. Every time it rains, the little green breaker on the GFDI trips off. That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes. This would mean removing the central modules to access the pass-through boxes. Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes. So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules. I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. How best (and safely) to track down where the ground fault is occurring? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. Bob Clark SolarWind Energy Systems, LLC ___ 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] Finding ground faults
A problem I have seen during my work with SiE is getting the tray covers on without pinching a wire, if one of the black plastic bolt guards was left off or lost, it could pinch, but they seem water-tight. I haven't run into any fault problems with SiE, but I see the possibilities. Keep me informed if you can. I have 3 11kW systems using SiE modules coming up this summer so I'm interested in where this is occurring. Jesse Sent from my iPad!!! On May 22, 2012, at 9:36 PM, Bob Clark bcl...@solar-wind.us wrote: Wrenches: Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings—not that 75-85 volts per string is all that low). We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers. The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. Up until this week the system has seen several weeks of awesome power production. Yesterday, the rains came and the GFDI breaker tripped. Every time it rains, the little green breaker on the GFDI trips off. That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes. This would mean removing the central modules to access the pass-through boxes. Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes. So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules. I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. How best (and safely) to track down where the ground fault is occurring? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. Bob Clark SolarWind Energy Systems, LLC ___ 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] Finding ground faults
Hey Bob ! Hi from the west side of the hill. This seems like an easy one... Well, maybe... One a dry day, take a garden hose and spray different parts of the system and see if you can duplicate the problem and locate where the water makes it trip. But you may have to wait a while for each spot sprayed to let it fault out before spraying another spot. That's how I'd start out. This also seems kind of weird in a way because of the current necessary for that breaker to trip. What ? 1/2 amp or 1.0 amp or so That's not a real small amount for rain. I bet something is rusty or corroded or something like that. Please let us know what you find !! boB On 5/22/2012 7:36 PM, Bob Clark wrote: Wrenches: Sorry to bring up this situation again, but I could not find a previous discussion thread that talked about step-by-step procedures for tracking down ground faults (I believe it was John Berdner who provided the bulk of the writing in that regard and it related to high voltage strings---not that 75-85 volts per string is all that low). We have an Outback FLEXpower Two system with 8, 3-module strings (Silicon Energy 190W, 25.3Vmp, 7.5 Imp) combined in a Midnite Solar MNPV12 combiner with breakers. The cables from the array are routed to two different Wiley 4-string pass-through boxes (located under the two center strings) and then off of the roof and into the PV combiner. Up until this week the system has seen several weeks of awesome power production. Yesterday, the rains came and the GFDI breaker tripped. Every time it rains, the little green breaker on the GFDI trips off. That tells me that the ground fault is occurring in a place where at least one of the conductors on one of the strings (possibly more) is getting wet and conducting current to ground. It would seem to me that the most likely place for moisture to cause a ground fault to occur in this system would be in the pass-through boxes. This would mean removing the central modules to access the pass-through boxes. Any of you who have mounted the Silicon Energy modules know that the cables are contained in trays along the side of the modules until they are routed through conduit to the pass-through boxes. So, if there is current going to ground from any of these cables, it could even be occurring in any of the 9 trays along side of the modules. I do not like the idea of tracking down a ground fault in one of these trays as they are all interconnected. How best (and safely) to track down where the ground fault is occurring? Any advice as to the best and safest way to track down the ground fault(s) would be greatly appreciated. *Bob Clark* */SolarWind Energy Systems, LLC/* ___ 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
