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On 7/19/2011 2:34 PM, David Brearley wrote:
<blockquote
cite="mid:CA4B628D.DBF3%25david.brearley@solarprofessional.com"
type="cite">
<title>Re: [RE-wrenches] 1987 NEC</title>
<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>
</span></font></blockquote>
<br>
<br>
The array shorting requirement must have gone away near 1993 or 1994
as<br>
I designed an opening and shorting of the array style GFPD version
in<br>
1994 while at Trace Engineering.<br>
<br>
It would have been expensive.<br>
<br>
boB<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<blockquote
cite="mid:CA4B628D.DBF3%25david.brearley@solarprofessional.com"
type="cite"><font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;">
<br>
<br>
On 7/19/11 3:29 PM, "Hans Frederickson" <<a
moz-do-not-send="true" href="hans@fredelectric.com">hans@fredelectric.com</a>>
wrote:<br>
<br>
</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>
</font></font><font face="Calibri, Verdana, Helvetica,
Arial"> <br>
</font><font color="#0000ff"><font face="Arial">Regards,<br>
-Hans</font></font><font face="Calibri, Verdana,
Helvetica, Arial"> <br>
<br>
<hr size="3" align="CENTER" width="100%"></font><font
face="Tahoma, Verdana, Helvetica, Arial"><b>From:</b> <a
moz-do-not-send="true"
href="re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a moz-do-not-send="true"
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>
</font><font face="Calibri, Verdana, Helvetica, Arial"><br>
Hans,<br>
<br>
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>
<br>
<a moz-do-not-send="true"
href="http://solarprofessional.com/article/?file=SP2_5_pg60_Mync">http://solarprofessional.com/article/?file=SP2_5_pg60_Mync</a><br>
<br>
“</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>
<br>
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>
<br>
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>
<br>
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>
<br>
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>
</span></font></font><font face="Calibri, Verdana,
Helvetica, Arial"><span style="font-size: 11pt;">
</span></font>
<p align="CENTER">
<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 </span></font></font>
</p>
<p>
<font size="1"><font face="Arial"><span style="font-size:
9pt;"><br>
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>
<br>
<br>
</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>
<br>
Best,<br>
</span></font><font size="1"><font face="Arial"><span
style="font-size: 9pt;"><br>
</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 moz-do-not-send="true"
href="david.brearley@solarprofessional.com">david.brearley@solarprofessional.com</a><br>
Direct: 541.261.6545<br>
<br>
<br>
On 7/19/11 2:19 PM, "Hans Frederickson" <<a
moz-do-not-send="true" href="hans@fredelectric.com">hans@fredelectric.com</a>>
wrote:<br>
<br>
</span></font></p>
<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>
</font></font><font face="Calibri, Verdana, Helvetica,
Arial"><br>
</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>
</font></font><font face="Calibri, Verdana, Helvetica,
Arial"><br>
</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>
</font></font><font face="Calibri, Verdana, Helvetica,
Arial"><br>
</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>
</font></font><font face="Calibri, Verdana, Helvetica,
Arial"><br>
</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>
</font></font><font face="Calibri, Verdana, Helvetica,
Arial"><br>
</font><font color="#0000ff"><font face="Arial">Regards,<br>
-Hans<br>
</font></font><font face="Calibri, Verdana, Helvetica,
Arial"><br>
<br>
<hr size="3" align="CENTER" width="100%"> </font><font
face="Tahoma, Verdana, Helvetica, Arial"><b>From:</b> <a
moz-do-not-send="true"
href="re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a moz-do-not-send="true"
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 moz-do-not-send="true"
href="gary@icarussolarservices.com">gary@icarussolarservices.com</a>;
RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] 1987 NEC<br>
</font><font face="Calibri, Verdana, Helvetica, Arial"><br>
Gary,<br>
<br>
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>
<br>
Kent Osterberg<br>
Blue Mountain Solar<br>
<br>
<br>
<br>
Gary Willett wrote: <br>
<br>
</font></span>
<blockquote><font face="Calibri, Verdana, Helvetica, Arial"><font
size="4"><span style="font-size: 14pt;">Kent:<br>
<br>
I am a member of the International Association of
Electrical Inspectors (IAEI), and they're
headquartered here in the Dallas area.<br>
<br>
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>
<br>
</span></font><span style="font-size: 11pt;"><br>
<br>
<br>
<br>
</span><font size="2"><span style="font-size: 10pt;">Regards,<br>
<br>
Gary Willett, PE<br>
<a moz-do-not-send="true"
href="Gary@IcarusSolarServices.com">Gary@IcarusSolarServices.com</a><br>
</span></font><span style="font-size: 11pt;"><br>
On 7/15/2011 4:30 PM, Kent Osterberg wrote: <br>
<br>
</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>
<br>
Kent Osterberg <br>
Blue Mountain Solar <br>
_______________________________________________ <br>
</span></font></blockquote>
</blockquote>
</blockquote>
<font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;"><br>
<br>
<br>
<hr size="3" align="CENTER" width="95%"></span></font></blockquote>
<font face="Calibri, Verdana, Helvetica, Arial"><span
style="font-size: 11pt;"><br>
<br>
<br>
</span></font>
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