Re: [RE-wrenches] 1987 NEC
Kent, I'm not a geezer yet, but thanks to my dad I do have a copy of the 1987 NEC. 690-5 (Ground Fault Detection and Interruption) was added in the 1990 NEC. There is no 690-5 or mention of ground fault detection/interruption in the 1987 NEC. In the 1990 NEC, section 690-5 is very small compared to 690.5 in the 2011 NEC. Here's the complete text from 1990: 690-5. Ground Fault Detection and Interruption. Roof-mounted photovoltaic arrays located on dwellings shall be provided with ground-fault protection to reduce fire hazard. The ground-fault protection circuit shall be capable of detecting a ground fault, interrupting the fault path, and disabling the array. The handbook for 1990 goes on to say that the gfp device must: 1) detect the ground fault 2) open the grounded conductor to interrupt the ground fault 3) open the ungrounded conductors and short the photoltaic array source to disable it For some reason, I've never heard of item #3, specifically the part about shorting the array. Can anyone shed light on this? Regards, -Hans _ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kent Osterberg Sent: Monday, July 18, 2011 10:07 PM To: g...@icarussolarservices.com; RE-wrenches Subject: Re: [RE-wrenches] 1987 NEC Gary, No one else has come up with a 1987 NEC. If you can get a copy of 1987 section 690.5 (I think it was 690-5 back then), I'd appreciate it. Kent Osterberg Blue Mountain Solar Gary Willett wrote: Kent: I am a member of the International Association of Electrical Inspectors (IAEI), and they're headquartered here in the Dallas area. If you aren't successful getting the info from a Wrench with the 1987 code book, let me know and I am sure I can request a FAXed copy of 1987 section 690.5. Regards, Gary Willett, PE g...@icarussolarservices.com On 7/15/2011 4:30 PM, Kent Osterberg wrote: I'm looking for the text of 1987 NEC 690.5 to compare with 2011 version. If any of you geezers have kept copies that old, please contact me off list. Thanks. Kent Osterberg Blue Mountain Solar ___ 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 ___ 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] 1987 NEC
Hans, John Wiles described the evolution of this standard for a Home Power article that we referenced later in a SolarPro on PV System Ground Faults: http://solarprofessional.com/article/?file=SP2_5_pg60_Mync ³As described by John Wiles, program manager for the Institute for the Energy and the Environment, in the February/ March 2008 Home Power article Ground-Fault Protection Is Expanding, Article 690.5 was added to the NEC in 1987. One of Wiles¹ first projects in the PV industry was to develop ³prototype hardware² to meet the new Code requirement. The basic concept (of the original GFPD prototype), writes Wiles, was to insert a 0.5- or 1-amp circuit breaker in the dc system-bonding conductor. This small circuit breaker senses any current between the grounded current-carrying conductor and the grounding system, tripping if current exceeds the 0.5 A or 1 A rating. By mechanically linking this smaller breaker to larger capacity breakers that are installed inline with the ungrounded current-carrying array conductors, it is possible to detect, interrupt and indicate that a ground fault has occurred, and to disconnect the fault. These early GFPDs were manufactured for 48 V or lower PV systems. According to Wiles, ³As higher voltage, utility-interactive PV inverters became available in the late 1990s, using a 0.5- or 1-amp fuse as the sensing element and the inverter¹s control electronics to monitor the fuse was more cost effective.² While the sensing equipment may have changed, in general the role of the modern GFPD remains the same as it was in 1987: 1. Detect ground faults in PV arrays. 2. Interrupt the fault current. 3. Indicate that a ground fault has occurred. 4. Disconnect the faulted part of the array. These four GFPD requirements for grounded PV arrays are spelled out in NEC 690.5(A) and 690.5(B). The former requires ground-fault detection and interruption (GFDI), which includes the provision to indicate the presence of a ground fault. The latter requires that faulted circuits be isolated either by disconnecting the ungrounded conductors of the faulted circuit or by shutting down power to the output power circuits of the inverter or charge controller. A final GFPD requirement is found in Article 960.5(C), which calls for a visible warning in the proximity of the ground-fault indicator. The warning could be an LED, an LCD or both. In general, the manufacturer provides this electric shock hazard warning as part of the listed grid-tied inverter or charge controller. However, where a PV system includes batteries, the installer must apply a duplicate warning label near the batteries, stating: WARNING ELECTRIC SHOCK HAZARD IF A GROUND FAULT IS INDICATED, NORMALLY GROUNDED CONDUCTORS MAY BE UNGROUNDED AND ENERGIZED One change in the GFPD requirements introduced in 1987 is that it is no longer necessary to short-circuit, or ³crowbar,² the PV array in the event of a ground fault. This added step had the effect of reducing the PV array voltage to zero, minimizing shock hazard. The requirement was dropped in a subsequent Code cycle, as leaving the array in a short-circuited condition created several other issues.² If you¹re a Home Power subscriber, you can access the original article in the HP archives. If not, it is summarized above. Best, David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer david.brear...@solarprofessional.com Direct: 541.261.6545 On 7/19/11 2:19 PM, Hans Frederickson h...@fredelectric.com wrote: Kent, I'm not a geezer yet, but thanks to my dad I do have a copy of the 1987 NEC. 690-5 (Ground Fault Detection and Interruption) was added in the 1990 NEC. There is no 690-5 or mention of ground fault detection/interruption in the 1987 NEC. In the 1990 NEC, section 690-5 is very small compared to 690.5 in the 2011 NEC. Here's the complete text from 1990: 690-5. Ground Fault Detection and Interruption. Roof-mounted photovoltaic arrays located on dwellings shall be provided with ground-fault protection to reduce fire hazard. The ground-fault protection circuit shall be capable of detecting a ground fault, interrupting the fault path, and disabling the array. The handbook for 1990 goes on to say that the gfp device must: 1) detect the ground fault 2) open the grounded conductor to interrupt the ground fault 3) open the ungrounded conductors and short the photoltaic array source to disable it For some reason, I've never heard of item #3, specifically the part about shorting the array. Can anyone shed light on this? Regards, -Hans From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kent Osterberg Sent: Monday, July 18, 2011 10:07 PM To: g...@icarussolarservices.com; RE-wrenches Subject: Re: [RE-wrenches] 1987 NEC Gary, No one else has come up with a 1987 NEC. If you can get a copy of 1987 section 690.5 (I think it was 690-5 back
Re: [RE-wrenches] 1987 NEC
David, Thanks for the interesting history on GFPDs. My copy of the 1987 NEC does not have 690-5, and it's not missing any pages. Either my code book is an incomplete printing or perhaps John Wiles was referring to a 1987 proposal that didn't make it into the code until the 1990 NEC. Regards, -Hans _ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of David Brearley Sent: Tuesday, July 19, 2011 12:57 PM To: RE-wrenches Subject: Re: [RE-wrenches] 1987 NEC Hans, John Wiles described the evolution of this standard for a Home Power article that we referenced later in a SolarPro on PV System Ground Faults: http://solarprofessional.com/article/?file=SP2_5_pg60_Mync As described by John Wiles, program manager for the Institute for the Energy and the Environment, in the February/ March 2008 Home Power article Ground-Fault Protection Is Expanding, Article 690.5 was added to the NEC in 1987. One of Wiles' first projects in the PV industry was to develop prototype hardware to meet the new Code requirement. The basic concept (of the original GFPD prototype), writes Wiles, was to insert a 0.5- or 1-amp circuit breaker in the dc system-bonding conductor. This small circuit breaker senses any current between the grounded current-carrying conductor and the grounding system, tripping if current exceeds the 0.5 A or 1 A rating. By mechanically linking this smaller breaker to larger capacity breakers that are installed inline with the ungrounded current-carrying array conductors, it is possible to detect, interrupt and indicate that a ground fault has occurred, and to disconnect the fault. These early GFPDs were manufactured for 48 V or lower PV systems. According to Wiles, As higher voltage, utility-interactive PV inverters became available in the late 1990s, using a 0.5- or 1-amp fuse as the sensing element and the inverter's control electronics to monitor the fuse was more cost effective. While the sensing equipment may have changed, in general the role of the modern GFPD remains the same as it was in 1987: 1. Detect ground faults in PV arrays. 2. Interrupt the fault current. 3. Indicate that a ground fault has occurred. 4. Disconnect the faulted part of the array. These four GFPD requirements for grounded PV arrays are spelled out in NEC 690.5(A) and 690.5(B). The former requires ground-fault detection and interruption (GFDI), which includes the provision to indicate the presence of a ground fault. The latter requires that faulted circuits be isolated either by disconnecting the ungrounded conductors of the faulted circuit or by shutting down power to the output power circuits of the inverter or charge controller. A final GFPD requirement is found in Article 960.5(C), which calls for a visible warning in the proximity of the ground-fault indicator. The warning could be an LED, an LCD or both. In general, the manufacturer provides this electric shock hazard warning as part of the listed grid-tied inverter or charge controller. However, where a PV system includes batteries, the installer must apply a duplicate warning label near the batteries, stating: WARNING ELECTRIC SHOCK HAZARD IF A GROUND FAULT IS INDICATED, NORMALLY GROUNDED CONDUCTORS MAY BE UNGROUNDED AND ENERGIZED One change in the GFPD requirements introduced in 1987 is that it is no longer necessary to short-circuit, or crowbar, the PV array in the event of a ground fault. This added step had the effect of reducing the PV array voltage to zero, minimizing shock hazard. The requirement was dropped in a subsequent Code cycle, as leaving the array in a short-circuited condition created several other issues. If you're a Home Power subscriber, you can access the original article in the HP archives. If not, it is summarized above. Best, David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer T david.brear...@solarprofessional.com Direct: 541.261.6545 On 7/19/11 2:19 PM, Hans Frederickson h...@fredelectric.com wrote: Kent, I'm not a geezer yet, but thanks to my dad I do have a copy of the 1987 NEC. 690-5 (Ground Fault Detection and Interruption) was added in the 1990 NEC. There is no 690-5 or mention of ground fault detection/interruption in the 1987 NEC. In the 1990 NEC, section 690-5 is very small compared to 690.5 in the 2011 NEC. Here's the complete text from 1990: 690-5. Ground Fault Detection and Interruption. Roof-mounted photovoltaic arrays located on dwellings shall be provided with ground-fault protection to reduce fire hazard. The ground-fault protection circuit shall be capable of detecting a ground fault, interrupting the fault path, and disabling the array. The handbook for 1990 goes on to say that the gfp device must: 1) detect the ground fault 2) open the grounded conductor to interrupt the ground fault 3) open the ungrounded conductors and short the photoltaic array source to disable it For some reason, I've
Re: [RE-wrenches] 1987 NEC
Thanks, David. I've been looking for a 1987 NEC because of this reference and others where John Wiles has referred to it. David Brearley wrote: Re: [RE-wrenches] 1987 NEC Hans, John Wiles described the evolution of this standard for a Home Power article that we referenced later in a SolarPro on PV System Ground Faults: http://solarprofessional.com/article/?file=SP2_5_pg60_Mync As described by John Wiles, program manager for the Institute for the Energy and the Environment, in the February/ March 2008 Home Power article "Ground-Fault Protection Is Expanding," Article 690.5 was added to theNECin 1987. One of Wiles first projects in the PV industry was to develop prototype hardware to meet the newCoderequirement. "The basic concept (of the original GFPD prototype)," writes Wiles, "was to insert a 0.5- or 1-amp circuit breaker in the dc system-bonding conductor." This small circuit breaker senses any current between the grounded current-carrying conductor and the grounding system, tripping if current exceeds the 0.5 A or 1 A rating. By mechanically linking this smaller breaker to larger capacity breakers that are installed inline with the ungrounded current-carrying array conductors, it is possible to detect, interrupt and indicate that a ground fault has occurred, and to disconnect the fault. These early GFPDs were manufactured for 48 V or lower PV systems. According to Wiles, As higher voltage, utility-interactive PV inverters became available in the late 1990s, using a 0.5- or 1-amp fuse as the sensing element and the inverters control electronics to monitor the fuse was more cost effective. While the sensing equipment may have changed, in general the role of the modern GFPD remains the same as it was in 1987: 1. Detect ground faults in PV arrays. 2. Interrupt the fault current. 3. Indicate that a ground fault has occurred. 4. Disconnect the faulted part of the array. These four GFPD requirements for grounded PV arrays are spelled out inNEC690.5(A) and 690.5(B). The former requires ground-fault detection and interruption (GFDI), which includes the provision to indicate the presence of a ground fault. The latter requires that faulted circuits be isolated either by disconnecting the ungrounded conductors of the faulted circuit or by shutting down power to the output power circuits of the inverter or charge controller. A final GFPD requirement is found in Article 960.5(C), which calls for a visible warning in the proximity of the ground-fault indicator. The warning could be an LED, an LCD or both. In general, the manufacturer provides this electric shock hazard warning as part of the listed grid-tied inverter or charge controller. However, where a PV system includes batteries, the installer must apply a duplicate warning label near the batteries, stating: WARNING ELECTRIC SHOCK HAZARD IF A GROUND FAULT IS INDICATED, NORMALLY GROUNDED CONDUCTORS MAY BE UNGROUNDED AND ENERGIZED One change in the GFPD requirements introduced in 1987 is that it is no longer necessary to short-circuit, or crowbar, the PV array in the event of a ground fault. This added step had the effect of reducing the PV array voltage to zero, minimizing shock hazard. The requirement was dropped in a subsequentCodecycle, as leaving the array in a short-circuited condition created several other issues. If youre a Home Power subscriber, you can access the original article in the HP archives. If not, it is summarized above. Best, David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer david.brear...@solarprofessional.com Direct: 541.261.6545 On 7/19/11 2:19 PM, "Hans Frederickson" h...@fredelectric.com wrote: Kent, I'm not a geezer yet, but thanks to my dad I do have a copy of the 1987 NEC. 690-5 (Ground Fault Detection and Interruption) was added in the 1990 NEC. There is no 690-5 or mention of ground fault detection/interruption in the 1987 NEC. In the 1990 NEC, section 690-5 is very small compared to 690.5 in the 2011 NEC. Here's the complete text from 1990: "690-5. Ground Fault Detection and Interruption. Roof-mounted photovoltaic arrays located on dwellings shall be provided with ground-fault protection to reduce fire hazard. The ground-fault protection circuit shall be capable of detecting a ground fault, interrupting the fault path, and disabling the array." The handbook for 1990 goes on to say that the gfp device must: 1) detect the ground fault 2) open the grounded conductor to interrupt the ground fault 3) open the ungrounded conductors and short the photoltaic array source to disable it For some reason, I've never heard of item #3, specifically the part about shorting the array. Can anyone shed light on this? Regards, -Hans From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wren
Re: [RE-wrenches] 1987 NEC
Thanks, Hans. The part about shorting the array was abandoned, I'm not sure but it may be have been removed for the 1993 code. It's item two on this list that I've been trying to backtrack to. It is pretty much the same as in the current code: "open the grounded conductor". It is also not the way things are actually done. The GFP fuse, circuit breaker, or PTC (Positive Temperature Coefficient) in inverters and now in some charge controllers opens the system bond (As described by John Wiles) not the grounded PV array conductor. Not openning the PV array grounded conductor means that not only is the normally grounded conductor in the PV array possibly energized (that can't be avoided), but everything else it is attached to is possibly energized. For battery based systems that includes: the battery negative terminal, battery vent fan wiring, and all dc loads. The fact that all dc loads may be energized to the potential of the PV array is troubling. Especially with the possibility now of a 600-volt PV array charging a battery system. Kent Osterberg Blue Mountain Solar Hans Frederickson wrote: Kent, I'm not a geezer yet, but thanks to my dad I dohave a copy of the 1987 NEC. 690-5 (Ground Fault Detection and Interruption) was added in the 1990 NEC. There is no690-5 ormention of ground fault detection/interruption in the 1987 NEC. In the 1990 NEC, section 690-5 is very small compared to 690.5 in the 2011 NEC. Here's the complete text from 1990: "690-5. Ground Fault Detection and Interruption. Roof-mounted photovoltaic arrays located on dwellings shall be provided with ground-fault protection to reduce fire hazard. The ground-fault protection circuit shall be capable of detecting a ground fault, interrupting the fault path, and disabling the array." The handbook for 1990 goes on to say that the gfp device must: 1) detect the ground fault 2) open the grounded conductor to interrupt the ground fault 3) open the ungrounded conductors and short the photoltaicarray source to disable it For some reason, I've never heard of item #3, specifically the part about shorting the array. Can anyone shed light on this? Regards, -Hans From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kent Osterberg Sent: Monday, July 18, 2011 10:07 PM To: g...@icarussolarservices.com; RE-wrenches Subject: Re: [RE-wrenches] 1987 NEC Gary, No one else has come up with a 1987 NEC. If you can get a copy of 1987 section 690.5 (I think it was 690-5 back then), I'd appreciate it. Kent Osterberg Blue Mountain Solar Gary Willett wrote: Kent: I am a member of the International Association of Electrical Inspectors (IAEI), and they're headquartered here in the Dallas area. If you aren't successful getting the info from a Wrench with the 1987 code book, let me know and I am sure I can request a FAXed copy of 1987 section 690.5. Regards, Gary Willett, PE g...@icarussolarservices.com On 7/15/2011 4:30 PM, Kent Osterberg wrote: I'm looking for the text of 1987 NEC 690.5 to compare with 2011 version. If any of you geezers have kept copies that old, please contact me off list. Thanks. Kent Osterberg Blue Mountain Solar ___ 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 ___ 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/option
Re: [RE-wrenches] 1987 NEC
We had an early 90s system with a DCGFP(complete with 4/0 GEC:)). A ground fault on a DC load circuit caused the GFP to lift the ground, shut the array off, but the short was still being fed by the battery and wouldn't trip the DC breaker, since negative was disconnected from ground. I thought it was fairly backwards and dangerous from what you would want to see in this situation. I still think this requirement causes more trouble than it fixes, especially on battery based off grid systems with DC loads. I'm looking forward to trying some of the smart combiner boxes to move us forward on this issue to real safety. Since we've had DCGFP for almost 20 years, has anyone seen these actually stop a dangerous situation? My experience is that the danger continues after the DCGFP trips, but at least you know something is wrong because after a week or so, the customer calls to complain that his array isn't charging. It's a rather complicated and less than fool proof idiot light. As Kent just pointed out: the situation is actually getting more dangerous with the higher voltages being used on off grid projects. R. Walters r...@solarray.com Solar Engineer Not openning the PV array grounded conductor means that not only is the normally grounded conductor in the PV array possibly energized (that can't be avoided), but everything else it is attached to is possibly energized. For battery based systems that includes: the battery negative terminal, battery vent fan wiring, and all dc loads. The fact that all dc loads may be energized to the potential of the PV array is troubling. Especially with the possibility now of a 600-volt PV array charging a battery system. Kent Osterberg Blue Mountain Solar ___ 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] 1987 NEC
Presumably the latteradded as part of the cycle of revisions initiated in 1987. On 7/19/11 3:29 PM, Hans Frederickson h...@fredelectric.com wrote: David, Thanks for the interesting history on GFPDs. My copy of the 1987 NEC does not have 690-5, and it's not missing any pages. Either my code book is an incomplete printing or perhaps John Wiles was referring to a 1987 proposal that didn't make it into the code until the 1990 NEC. Regards, -Hans From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of David Brearley Sent: Tuesday, July 19, 2011 12:57 PM To: RE-wrenches Subject: Re: [RE-wrenches] 1987 NEC Hans, John Wiles described the evolution of this standard for a Home Power article that we referenced later in a SolarPro on PV System Ground Faults: http://solarprofessional.com/article/?file=SP2_5_pg60_Mync ³As described by John Wiles, program manager for the Institute for the Energy and the Environment, in the February/ March 2008 Home Power article Ground-Fault Protection Is Expanding, Article 690.5 was added to the NEC in 1987. One of Wiles¹ first projects in the PV industry was to develop ³prototype hardware² to meet the new Code requirement. The basic concept (of the original GFPD prototype), writes Wiles, was to insert a 0.5- or 1-amp circuit breaker in the dc system-bonding conductor. This small circuit breaker senses any current between the grounded current-carrying conductor and the grounding system, tripping if current exceeds the 0.5 A or 1 A rating. By mechanically linking this smaller breaker to larger capacity breakers that are installed inline with the ungrounded current-carrying array conductors, it is possible to detect, interrupt and indicate that a ground fault has occurred, and to disconnect the fault. These early GFPDs were manufactured for 48 V or lower PV systems. According to Wiles, ³As higher voltage, utility-interactive PV inverters became available in the late 1990s, using a 0.5- or 1-amp fuse as the sensing element and the inverter¹s control electronics to monitor the fuse was more cost effective.² While the sensing equipment may have changed, in general the role of the modern GFPD remains the same as it was in 1987: 1. Detect ground faults in PV arrays. 2. Interrupt the fault current. 3. Indicate that a ground fault has occurred. 4. Disconnect the faulted part of the array. These four GFPD requirements for grounded PV arrays are spelled out in NEC 690.5(A) and 690.5(B). The former requires ground-fault detection and interruption (GFDI), which includes the provision to indicate the presence of a ground fault. The latter requires that faulted circuits be isolated either by disconnecting the ungrounded conductors of the faulted circuit or by shutting down power to the output power circuits of the inverter or charge controller. A final GFPD requirement is found in Article 960.5(C), which calls for a visible warning in the proximity of the ground-fault indicator. The warning could be an LED, an LCD or both. In general, the manufacturer provides this electric shock hazard warning as part of the listed grid-tied inverter or charge controller. However, where a PV system includes batteries, the installer must apply a duplicate warning label near the batteries, stating: WARNING ELECTRIC SHOCK HAZARD IF A GROUND FAULT IS INDICATED, NORMALLY GROUNDED CONDUCTORS MAY BE UNGROUNDED AND ENERGIZED One change in the GFPD requirements introduced in 1987 is that it is no longer necessary to short-circuit, or ³crowbar,² the PV array in the event of a ground fault. This added step had the effect of reducing the PV array voltage to zero, minimizing shock hazard. The requirement was dropped in a subsequent Code cycle, as leaving the array in a short-circuited condition created several other issues.² If you¹re a Home Power subscriber, you can access the original article in the HP archives. If not, it is summarized above. Best, David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer david.brear...@solarprofessional.com Direct: 541.261.6545 On 7/19/11 2:19 PM, Hans Frederickson h...@fredelectric.com wrote: Kent, I'm not a geezer yet, but thanks to my dad I do have a copy of the 1987 NEC. 690-5 (Ground Fault Detection and Interruption) was added in the 1990 NEC. There is no 690-5 or mention of ground fault detection/interruption in the 1987 NEC. In the 1990 NEC, section 690-5 is very small compared to 690.5 in the 2011 NEC. Here's the complete text from 1990: 690-5. Ground Fault Detection and Interruption. Roof-mounted photovoltaic arrays located on dwellings shall be provided with ground-fault protection to reduce fire hazard. The ground-fault protection circuit shall be capable of detecting a ground fault, interrupting the fault path, and disabling the array
Re: [RE-wrenches] 1987 NEC
On 7/19/2011 2:34 PM, David Brearley wrote: Presumably the latter---added as part of the cycle of revisions initiated in 1987. The array shorting requirement must have gone away near 1993 or 1994 as I designed an opening and shorting of the array style GFPD version in 1994 while at Trace Engineering. It would have been expensive. boB On 7/19/11 3:29 PM, Hans Frederickson h...@fredelectric.com wrote: David, Thanks for the interesting history on GFPDs. My copy of the 1987 NEC does not have 690-5, and it's not missing any pages. Either my code book is an incomplete printing or perhaps John Wiles was referring to a 1987 proposal that didn't make it into the code until the 1990 NEC. Regards, -Hans *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *David Brearley *Sent:* Tuesday, July 19, 2011 12:57 PM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] 1987 NEC Hans, John Wiles described the evolution of this standard for a Home Power article that we referenced later in a SolarPro on PV System Ground Faults: http://solarprofessional.com/article/?file=SP2_5_pg60_Mync As described by John Wiles, program manager for the Institute for the Energy and the Environment, in the February/ March 2008 Home Power article Ground-Fault Protection Is Expanding, Article 690.5 was added to the /NEC/ in 1987. One of Wiles' first projects in the PV industry was to develop prototype hardware to meet the new /Code/ requirement. The basic concept (of the original GFPD prototype), writes Wiles, was to insert a 0.5- or 1-amp circuit breaker in the dc system-bonding conductor. This small circuit breaker senses any current between the grounded current-carrying conductor and the grounding system, tripping if current exceeds the 0.5 A or 1 A rating. By mechanically linking this smaller breaker to larger capacity breakers that are installed inline with the ungrounded current-carrying array conductors, it is possible to detect, interrupt and indicate that a ground fault has occurred, and to disconnect the fault. These early GFPDs were manufactured for 48 V or lower PV systems. According to Wiles, As higher voltage, utility-interactive PV inverters became available in the late 1990s, using a 0.5- or 1-amp fuse as the sensing element and the inverter's control electronics to monitor the fuse was more cost effective. While the sensing equipment may have changed, in general the role of the modern GFPD remains the same as it was in 1987: 1. Detect ground faults in PV arrays. 2. Interrupt the fault current. 3. Indicate that a ground fault has occurred. 4. Disconnect the faulted part of the array. These four GFPD requirements for grounded PV arrays are spelled out in /NEC/ 690.5(A) and 690.5(B). The former requires ground-fault detection and interruption (GFDI), which includes the provision to indicate the presence of a ground fault. The latter requires that faulted circuits be isolated either by disconnecting the ungrounded conductors of the faulted circuit or by shutting down power to the output power circuits of the inverter or charge controller. A final GFPD requirement is found in Article 960.5(C), which calls for a visible warning in the proximity of the ground-fault indicator. The warning could be an LED, an LCD or both. In general, the manufacturer provides this electric shock hazard warning as part of the listed grid-tied inverter or charge controller. However, where a PV system includes batteries, the installer must apply a duplicate warning label near the batteries, stating: WARNING ELECTRIC SHOCK HAZARD IF A GROUND FAULT IS INDICATED, NORMALLY GROUNDED CONDUCTORS MAY BE UNGROUNDED AND ENERGIZED One change in the GFPD requirements introduced in 1987 is that it is no longer necessary to short-circuit, or crowbar, the PV array in the event of a ground fault. This added step had the effect of reducing the PV array voltage to zero, minimizing shock hazard. The requirement was dropped in a subsequent /Code/ cycle, as leaving the array in a short-circuited condition created several other issues. If you're a Home Power subscriber, you can access the original article in the HP archives. If not, it is summarized above. Best, David Brearley, Senior Technical Editor /SolarPro/ magazine NABCEP Certified PV Installer ^(TM) david.brear...@solarprofessional.com Direct: 541.261.6545 On 7/19/11 2:19 PM, Hans Frederickson h...@fredelectric.com wrote: Kent, I'm not a geezer yet, but thanks to my dad I do have a copy of the 1987 NEC
Re: [RE-wrenches] 1987 NEC
Gary, No one else has come up with a 1987 NEC. If you can get a copy of 1987 section 690.5 (I think it was 690-5 back then), I'd appreciate it. Kent Osterberg Blue Mountain Solar Gary Willett wrote: Kent: I am a member of the International Association of Electrical Inspectors (IAEI), and they're headquartered here in the Dallas area. If you aren't successful getting the info from a Wrench with the 1987 code book, let me know and I am sure I can request a FAXed copy of 1987 section 690.5. Regards, Gary Willett, PE g...@icarussolarservices.com On 7/15/2011 4:30 PM, Kent Osterberg wrote: I'm looking for the text of 1987 NEC 690.5 to compare with 2011 version. If any of you geezers have kept copies that old, please contact me off list. Thanks. Kent Osterberg Blue Mountain Solar ___ 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 ___ 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] 1987 NEC
I'm looking for the text of 1987 NEC 690.5 to compare with 2011 version. If any of you geezers have kept copies that old, please contact me off list. Thanks. Kent Osterberg Blue Mountain Solar ___ 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] 1987 NEC
Kent: I am a member of the International Association of Electrical Inspectors (IAEI), and they're headquartered here in the Dallas area. If you aren't successful getting the info from a Wrench with the 1987 code book, let me know and I am sure I can request a FAXed copy of 1987 section 690.5. Regards, Gary Willett, PE g...@icarussolarservices.com mailto:g...@icarussolarservices.com On 7/15/2011 4:30 PM, Kent Osterberg wrote: I'm looking for the text of 1987 NEC 690.5 to compare with 2011 version. If any of you geezers have kept copies that old, please contact me off list. Thanks. Kent Osterberg Blue Mountain Solar ___ 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
