<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="Generator" content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Verdana;
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","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Verdana","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:1551304657;
mso-list-type:hybrid;
mso-list-template-ids:1730820682 67698703 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l0:level1
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level2
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
@list l0:level4
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level5
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level6
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
@list l0:level7
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level8
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level9
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
ol
{margin-bottom:0in;}
ul
{margin-bottom:0in;}
--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d">Matt:</span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d">This connection is not advised for these reasons: </span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d"> </span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-family:"Verdana","sans-serif";color:#1f497d"><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-family:"Verdana","sans-serif";color:#1f497d">The assumption is that two controllers were installed because one charge controller could not handle the charging duties. Due to small differences in manufacturing tolerances, charge controllers never operate at exactly equal values. The charge controller working harder will get warmer. Thermal runaway is possible with the harder working charge controller working harder and harder until it is passing all of the charging current, exceeding its rating and risking damage, overheating and attendant fire risks.</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-family:"Verdana","sans-serif";color:#1f497d"><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-family:"Verdana","sans-serif";color:#1f497d">If two of this particular charge controller are installed, one is supposed to act as GFDI enabled device. Cross connecting negatives could defeat this function.</span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d">As usual, there is no substitute to doing a job correctly. </span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d">William</span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1f497d">Miller Solar</span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1f497d">17395 Oak Road, Atascadero, CA 93422</span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1f497d">805-438-5600</span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1f497d"><a href="http://www.millersolar.com/"><span style="color:blue">www.millersolar.com</span></a></span></p><p class="MsoNormal"><span style="font-family:"Arial","sans-serif";color:#1f497d">CA Lic. 773985</span></p><p class="MsoNormal"><span style="font-family:"Verdana","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> RE-wrenches [mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Matt Sherald<br><b>Sent:</b> Thursday, November 7, 2019 11:46 AM<br><b>To:</b> RE-wrenches<br><b>Subject:</b> [RE-wrenches] Two MPPT Charge Controllers, One PV Circuit</span></p><p class="MsoNormal"> </p><div><div><p class="MsoNormal">Hi All,</p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">I recently posted a request for suggestions regarding a 600Vdc xfer switch. In the intervening time, I've been out to visit and review the system in question and found that the original installer had been called back and had added a second XW MPPT 80.</p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">The installer did not run separate strings to each of the two MPPTs, but instead they split the PV output circuit with split bolts and now feed the two MPPTs from this splice. A Schneider tech whom I spoke with said that this was a safety issue, but was unable to clearly explain why it posed a danger. Can anyone lend some insight? I can imagine how the MPPT function might be skewed, but the wire size of the feeders are adequate for the combined current of the full PV array and the units are producing power. </p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">-Matt</p></div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">I'd like to give the system owner advice with t </p></div><div><p class="MsoNormal"><br>-- </p><div><div><div><div><div><p class="MsoNormal">Matt Sherald</p></div><p class="MsoNormal">PIMBY Energy, LLC</p></div><div><p class="MsoNormal">NABCEP Certified Solar PV Installer®</p></div><div><p class="MsoNormal" style="margin-bottom:12.0pt">304-704-5943</p></div><p class="MsoNormal"><a href="http://www.getpimby.blogspot.com" target="_blank">www.getpimby.blogspot.com</a><br><a href="http://www.getpimby.com" target="_blank">www.getpimby.com</a></p></div><p class="MsoNormal"> </p></div></div></div></div></div></body></html>