<html>
<head>
<meta http-equiv=Content-Type content="text/html; charset=us-ascii">
<meta name=Generator content="Microsoft Word 11 (filtered)">
<style>
<!--
/* Font Definitions */
@font-face
{font-family:"Arial Narrow";
panose-1:2 11 5 6 2 2 2 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
h1
{margin-top:12.0pt;
margin-right:0in;
margin-bottom:3.0pt;
margin-left:0in;
page-break-after:avoid;
font-size:16.0pt;
font-family:Arial;
font-weight:bold;}
h3
{margin-top:6.0pt;
margin-right:0in;
margin-bottom:0in;
margin-left:0in;
margin-bottom:.0001pt;
page-break-after:avoid;
font-size:12.0pt;
font-family:Arial;
letter-spacing:-.5pt;
font-weight:normal;}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:blue;
text-decoration:underline;}
p
{margin-right:0in;
margin-left:0in;
font-size:12.0pt;
font-family:"Times New Roman";}
p.alist, li.alist, div.alist
{margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
text-indent:-.15in;
font-size:12.0pt;
font-family:"Times New Roman";}
p.ahead3, li.ahead3, div.ahead3
{margin-top:6.0pt;
margin-right:0in;
margin-bottom:0in;
margin-left:0in;
margin-bottom:.0001pt;
page-break-after:avoid;
font-size:12.0pt;
font-family:Arial;
letter-spacing:-.5pt;}
p.StyleaparaJustifiedAfter0pt, li.StyleaparaJustifiedAfter0pt, div.StyleaparaJustifiedAfter0pt
{margin:0in;
margin-bottom:.0001pt;
text-align:justify;
font-size:12.0pt;
font-family:"Arial Narrow";}
p.alistnead, li.alistnead, div.alistnead
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:Arial;}
p.anumlist, li.anumlist, div.anumlist
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
p.aHead1, li.aHead1, div.aHead1
{margin-top:0in;
margin-right:0in;
margin-bottom:6.0pt;
margin-left:0in;
text-align:center;
page-break-after:avoid;
font-size:16.0pt;
font-family:Arial;
font-weight:bold;}
p.StyleHeading3Left0Firstline0, li.StyleHeading3Left0Firstline0, div.StyleHeading3Left0Firstline0
{margin-top:6.0pt;
margin-right:0in;
margin-bottom:0in;
margin-left:0in;
margin-bottom:.0001pt;
page-break-after:avoid;
font-size:12.0pt;
font-family:Arial;
letter-spacing:-.5pt;}
p.a-text, li.a-text, div.a-text
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
p.apara, li.apara, div.apara
{margin:0in;
margin-bottom:.0001pt;
text-indent:.35in;
font-size:12.0pt;
font-family:"Times New Roman";}
p.StyleHeading1Centered, li.StyleHeading1Centered, div.StyleHeading1Centered
{margin-top:0in;
margin-right:0in;
margin-bottom:6.0pt;
margin-left:.5in;
text-align:center;
page-break-after:avoid;
font-size:16.0pt;
font-family:Arial;
font-weight:bold;}
p.Styleapara1TimesNewRomanFirstline025, li.Styleapara1TimesNewRomanFirstline025, div.Styleapara1TimesNewRomanFirstline025
{margin:0in;
margin-bottom:.0001pt;
text-align:justify;
text-indent:.25in;
font-size:12.0pt;
font-family:"Times New Roman";
letter-spacing:-.25pt;}
p.PPAhead, li.PPAhead, div.PPAhead
{margin:0in;
margin-bottom:.0001pt;
font-size:16.0pt;
font-family:Arial;}
p.aparabullet, li.aparabullet, div.aparabullet
{margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
text-align:justify;
text-indent:-.25in;
font-size:12.0pt;
font-family:"Times New Roman";
letter-spacing:-.25pt;}
p.AAbulllist1, li.AAbulllist1, div.AAbulllist1
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
p.AAbulllist2, li.AAbulllist2, div.AAbulllist2
{margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:1.0in;
margin-bottom:.0001pt;
text-indent:-.25in;
font-size:12.0pt;
font-family:"Times New Roman";}
p.styleaparajustifiedafter0pt0, li.styleaparajustifiedafter0pt0, div.styleaparajustifiedafter0pt0
{margin:0in;
margin-bottom:.0001pt;
text-align:justify;
font-size:12.0pt;
font-family:"Arial Narrow";}
p.alistnead0, li.alistnead0, div.alistnead0
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:Arial;}
p.ahead10, li.ahead10, div.ahead10
{margin-top:0in;
margin-right:0in;
margin-bottom:6.0pt;
margin-left:0in;
text-align:center;
page-break-after:avoid;
font-size:16.0pt;
font-family:Arial;
font-weight:bold;}
p.styleheading3left0firstline00, li.styleheading3left0firstline00, div.styleheading3left0firstline00
{margin-top:6.0pt;
margin-right:0in;
margin-bottom:0in;
margin-left:0in;
margin-bottom:.0001pt;
page-break-after:avoid;
font-size:12.0pt;
font-family:Arial;
letter-spacing:-.5pt;}
p.styleheading1centered0, li.styleheading1centered0, div.styleheading1centered0
{margin-top:0in;
margin-right:0in;
margin-bottom:6.0pt;
margin-left:.5in;
text-align:center;
page-break-after:avoid;
font-size:16.0pt;
font-family:Arial;
font-weight:bold;}
p.styleapara1timesnewromanfirstline0250, li.styleapara1timesnewromanfirstline0250, div.styleapara1timesnewromanfirstline0250
{margin:0in;
margin-bottom:.0001pt;
text-align:justify;
text-indent:.25in;
font-size:12.0pt;
font-family:"Times New Roman";
letter-spacing:-.25pt;}
p.ppahead0, li.ppahead0, div.ppahead0
{margin:0in;
margin-bottom:.0001pt;
font-size:16.0pt;
font-family:Arial;}
p.aabulllist10, li.aabulllist10, div.aabulllist10
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman";}
p.aabulllist20, li.aabulllist20, div.aabulllist20
{margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:1.0in;
margin-bottom:.0001pt;
text-indent:-.25in;
font-size:12.0pt;
font-family:"Times New Roman";}
span.emailstyle32
{color:black;}
span.EmailStyle43
{color:black;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;}
div.Section1
{page:Section1;}
/* List Definitions */
ol
{margin-bottom:0in;}
ul
{margin-bottom:0in;}
-->
</style>
</head>
<body lang=EN-US link=blue vlink=blue>
<div class=Section1>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'>The only thing I am aware of wrt to fused
DC discos is the notion that PV runs that penetrate a building shell need over
current protection. The City of Santa Monica used to (and may still) have this
requirement.</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'> </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'>The (non) issues as I understand them:</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in'><font size=3
color=black face="Times New Roman"><span style='font-size:12.0pt;color:black'>(1)</span></font><font
size=1 color=black><span style='font-size:7.0pt;color:black'> </span></font><font
color=black><span style='color:black'>PV modules should be treated as any other
independent source, regardless of the fact that they are inherently current
limited. It would be straightforward to determine whether or not the wire used
has the adequate ampacity.</span></font></p>
<p class=MsoNormal style='margin-left:.5in;text-indent:-.25in'><font size=3
color=black face="Times New Roman"><span style='font-size:12.0pt;color:black'>(2)</span></font><font
size=1 color=black><span style='font-size:7.0pt;color:black'> </span></font><font
color=black><span style='color:black'>Inverters may be capable of back-feeding
the PV array . Manufacturers that continue to sell and market a specific
inverter model, are usually willing to write a letter to the effect that
back-feeding will not occur. The only mfgr that I know of that demurred is
Sharp wrt their JH-3500,<b><i><span style='font-weight:bold;font-style:italic'>
</span></i></b>and it is no longer sold in the US.</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'> </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'>Of course the use of an unfused disco
makes good sense, prior to penetrating building shell. </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'> </span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'>- Peter</span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'> </span></font></p>
<div>
<p><font size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:
Arial;color:navy'>Peter T. Parrish, Ph.D., President<br>
California Solar Engineering, Inc.<br>
820 Cynthia Ave., Los Angeles, CA 90065<br>
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885<br>
CA Lic. 854779, NABCEP Cert. 031806-26<br>
peter.parrish@calsolareng.com</span></font><font size=2 color=blue face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:blue'> </span></font></p>
</div>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>ASAP POWER! 2<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, November 21, 2008
10:47 AM<br>
<b><span style='font-weight:bold'>To:</span></b> 'RE-wrenches'<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [RE-wrenches] DC
Rating of Disconnects</span></font></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Tahoma><span style='font-size:
10.0pt;font-family:Tahoma;color:navy'>In 2008, we have had to replace our
standard Sq. D HU361RB used since our beginnings, with the Sq. D H361RB (U
stands for unfused). Was there some sort of code change NEC or CBC
maybe that made most jurisdictions in So Cal suddenly start requiring fused DC
disconnects? Typically, we fill the fused Sq. D. box with 15A 5"
fuses.</span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 color=navy face=Tahoma><span style='font-size:
10.0pt;font-family:Tahoma;color:navy'>Peter D.</span></font></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabIndex=-1>
</span></font></div>
<p class=MsoNormal style='margin-bottom:12.0pt'><b><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>William Miller<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, November 21, 2008
9:43 AM<br>
<b><span style='font-weight:bold'>To:</span></b> RE-wrenches<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [RE-wrenches] DC
Rating of Disconnects</span></font></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Peter:<br>
<br>
I am resending, the first version inexplicably deleted some text:<br>
<br>
An arc is created in the process of disconnecting any current under load.
DC circuits have an enhanced ability to sustain that arc. PV circuits
exacerbate this problem as a short or load is disconnected because they can
sustain a short but the voltage rises drastically as a circuit is disconnected.<br>
<br>
This all justifies the added expense of a DC rated disconnect. We use the
Square D HU361 without hesitation. There are few alternatives available
and none with any significant cost savings. In selecting a disconnect, a
design-build contractor must use the highest Voc possible. Make sure you are
entering the 690.7 table with the record low temperature for the location.<br>
<br>
If we used a disconnect without the correct rating we would open ourselves to
unacceptable liability exposure and, worse yet, would not experience that
pleasant feeling one gets when you know you've done the job right.<br>
<br>
William Miller<br>
<br>
<br>
At 09:11 AM 11/21/2008, you wrote:</span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=2
color=blue face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:blue'>
<hr size=2 width="100%" align=center>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'> Peter Parrish [<a
href="mailto:peter.parrish@calsolareng.com" eudora=autourl>mailto:peter.parrish@calsolareng.com</a>]
<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, November 21, 2008
9:10 AM<br>
<b><span style='font-weight:bold'>To:</span></b> 'RE-wrenches'<br>
<b><span style='font-weight:bold'>Cc:</span></b> 'Peter Parrish'<br>
<b><span style='font-weight:bold'>Subject:</span></b> DC Rating of Disconnects<br>
</span></font><font face=Arial><span style='font-family:Arial'> <br>
I am looking into using the PV Powered PVP2000 inverter for some small, low
voltage designs. The string Voc will be around 200 Vdc, worst case.<br>
<br>
Since the PVP2000 doesnt come with a DC disconnect, I am wondered what
other wrenches who install the PVP2000 have been doing about this. I hate to
spend $150 on a 600 V AC/DC disco such as the SD HU361RB to provide the means
of disconnection. I believe that the 240 V AC discos such as the SD DU221RB
have no DC rating.<br>
<br>
>From an academic point of view, I wonder why the smaller discos are not dual
rated, since we all know that the real-time voltage difference in a 240 V AC
system can be 41% greater than 240 V.<br>
<br>
In any event, any Code-compliant solutions would be greatly appreciated.<br>
<br>
- Peter<br>
</span></font><br>
<font size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:
Arial;color:navy'>Peter T. Parrish, President</span></font></p>
</div>
</body>
</html>