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<FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Presumably the latter—added as part of the cycle of revisions initiated in 1987. <BR>
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On 7/19/11 3:29 PM, "Hans Frederickson" <<a href="hans@fredelectric.com">hans@fredelectric.com</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><SPAN STYLE='font-size:11pt'><FONT COLOR="#0000FF"><FONT FACE="Arial">David,<BR>
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. <BR>
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</FONT><FONT COLOR="#0000FF"><FONT FACE="Arial">Regards,<BR>
-Hans</FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"> <BR>
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<HR ALIGN=CENTER SIZE="3" WIDTH="100%"></FONT><FONT FACE="Tahoma, Verdana, Helvetica, Arial"><B>From:</B> <a href="re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a> [<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <B>On Behalf Of </B>David Brearley<BR>
<B>Sent:</B> Tuesday, July 19, 2011 12:57 PM<BR>
<B>To:</B> RE-wrenches<BR>
<B>Subject:</B> Re: [RE-wrenches] 1987 NEC<BR>
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Hans,<BR>
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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:<BR>
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<a href="http://solarprofessional.com/article/?file=SP2_5_pg60_Mync">http://solarprofessional.com/article/?file=SP2_5_pg60_Mync</a><BR>
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“</FONT></SPAN><FONT SIZE="1"><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>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 <I>NEC</I> in 1987. One of Wiles’ first projects in the PV industry was to develop “prototype hardware” to meet the new <I>Code</I> 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.<BR>
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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:<BR>
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1. Detect ground faults in PV arrays. <BR>
2. Interrupt the fault current. <BR>
3. Indicate that a ground fault has occurred. <BR>
4. Disconnect the faulted part of the array.<BR>
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These four GFPD requirements for grounded PV arrays are spelled out in <I>NEC</I> 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.<BR>
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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:<BR>
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<FONT SIZE="1"><FONT FACE="Arial"><SPAN STYLE='font-size:9pt'>WARNING <BR>
ELECTRIC SHOCK HAZARD <BR>
IF A GROUND FAULT IS INDICATED, NORMALLY <BR>
GROUNDED CONDUCTORS MAY BE UNGROUNDED <BR>
AND ENERGIZED
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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 <I>Code</I> cycle, as leaving the array in a short-circuited condition created several other issues.”<BR>
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</SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>If you’re a Home Power subscriber, you can access the original article in the HP archives. If not, it is summarized above.<BR>
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Best,<BR>
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</SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>David Brearley, Senior Technical Editor<BR>
<I>SolarPro</I> magazine <BR>
NABCEP Certified PV Installer ™<BR>
<a href="david.brearley@solarprofessional.com">david.brearley@solarprofessional.com</a><BR>
Direct: 541.261.6545<BR>
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On 7/19/11 2:19 PM, "Hans Frederickson" <<a href="hans@fredelectric.com">hans@fredelectric.com</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><SPAN STYLE='font-size:11pt'><FONT COLOR="#0000FF"><FONT FACE="Arial">Kent,<BR>
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.<BR>
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</FONT><FONT COLOR="#0000FF"><FONT FACE="Arial">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:<BR>
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</FONT><FONT COLOR="#0000FF"><FONT FACE="Arial">"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."<BR>
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</FONT><FONT COLOR="#0000FF"><FONT FACE="Arial">The handbook for 1990 goes on to say that the gfp device must:<BR>
1) detect the ground fault<BR>
2) open the grounded conductor to interrupt the ground fault<BR>
3) open the ungrounded conductors and short the photoltaic array source to disable it<BR>
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</FONT><FONT COLOR="#0000FF"><FONT FACE="Arial">For some reason, I've never heard of item #3, specifically the part about shorting the array. Can anyone shed light on this?<BR>
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</FONT><FONT COLOR="#0000FF"><FONT FACE="Arial">Regards,<BR>
-Hans<BR>
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<HR ALIGN=CENTER SIZE="3" WIDTH="100%"> </FONT><FONT FACE="Tahoma, Verdana, Helvetica, Arial"><B>From:</B> <a href="re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a> [<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <B>On Behalf Of </B>Kent Osterberg<BR>
<B>Sent:</B> Monday, July 18, 2011 10:07 PM<BR>
<B>To:</B> <a href="gary@icarussolarservices.com">gary@icarussolarservices.com</a>; RE-wrenches<BR>
<B>Subject:</B> Re: [RE-wrenches] 1987 NEC<BR>
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Gary,<BR>
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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.<BR>
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Kent Osterberg<BR>
Blue Mountain Solar<BR>
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Gary Willett wrote: <BR>
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</FONT></SPAN><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><FONT SIZE="4"><SPAN STYLE='font-size:14pt'>Kent:<BR>
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I am a member of the International Association of Electrical Inspectors (IAEI), and they're headquartered here in the Dallas area.<BR>
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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.<BR>
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</SPAN><FONT SIZE="2"><SPAN STYLE='font-size:10pt'>Regards,<BR>
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Gary Willett, PE<BR>
<a href="Gary@IcarusSolarServices.com">Gary@IcarusSolarServices.com</a><BR>
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On 7/15/2011 4:30 PM, Kent Osterberg wrote: <BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>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. <BR>
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Kent Osterberg <BR>
Blue Mountain Solar <BR>
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