<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">I have always thought it was the same calculation as the Fault current as calculated in NFPA 70E. but I will ask some one whom I respect.<br>Darryl<br><br>--- On <b>Sun, 3/28/10, R Ray Walters <i><ray@solarray.com></i></b> wrote:<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>From: R Ray Walters <ray@solarray.com><br>Subject: Re: [RE-wrenches] Supply Side Tap Overcurrent Protection<br>To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br>Date: Sunday, March 28, 2010, 11:45 PM<br><br><div id="yiv233937764">This brings up a related question, that I can't seem to find an NEC answer to: How do we calculate the available fault current, for picking our AIC rating?<div>I used to always throw 20,000 amps AIC rating fuses and breakers for large battery banks, but on grid, it seems we
would have to know things like the rating of the utility's upstream transformer, etc.</div><div>to really know the proper AIC to use.</div><div>The code mentions how important AIC is in several sections, but never explains how to calculate it. Did I just fall a sleep that day in Code class?</div><div>Seems that even a fused disconnect could be suspect, if they put in the wrong fuses. </div><div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-indent: 0px; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px;"><div>R. Walters</div><div><a rel="nofollow" ymailto="mailto:ray@solarray.com" target="_blank" href="/mc/compose?to=ray@solarray.com">ray@solarray.com</a></div><div>Solar Engineer</div><div><br class="khtml-block-placeholder"></div><div><br class="khtml-block-placeholder"></div><br class="Apple-interchange-newline"></span>
</div>
<br><div><div>On Mar 28, 2010, at 1:08 PM, Bob-O Schultze wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div style="word-wrap: break-word;">Dave,<div>OK, here's my shot at this. Your mileage may vary. I think 240.86(A) applies here. Unless the CB in the Xantrex XW has a higher interrupt ratting (AIC) than the available fault current from that supply side tap and the CB is so marked (240.83(C), a disconnect using appropriate current limiting OCD devices is required. I've never done a supply side tap without the disco being fused with current limiting fuses, nor have I ever heard of one that wasn't current limit protected being approved.</div><div>Good Luck, Bob-O</div><div>ps you travel without your Code book? :)</div><div><br></div><div><br></div><div><div><div>On Mar 28, 2010, at 10:52 AM, Dave Palumbo wrote:</div><br class="Apple-interchange-newline"><span class="Apple-style-span" style="border-collapse:
separate; font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><div lang="EN-US"><div class="Section1"><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;">Wrenches,</span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;">I am tasked with reviewing an installation by a licensed electrician in Vermont and would like help with the following:</span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family:
Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;">Grid-tied PV system with battery back-up. AC point of connection is a supply side tap (done on customer side of utility meter ) then traveling 5 feet of #2 THHWN in 1β EMT to the 60 Amp 240vac Lockable Utility Disconnect (unfused) and continuing 15 feet #2 THHWN 1β EMT to Xantrex XW 60 Amp breaker.</span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;">I had said that the 60amp 240vac lockable disconnect needed to be fused, and received the following reply from the
installing electrician.<i></i></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><i><span style="font-size: 12pt; font-family: serif;"> </span></i></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><i><span style="font-size: 12pt; font-family: serif;"><< βThe Xantrex XW Power Distribution Panel contains the required over current protection (60 amp</span></i></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><i><span style="font-size: 12pt; font-family: serif;">double pole circuit breaker) negating the need for a redundant fuse at the Utility Disconnect switch.β >></span></i></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><i><span style="font-size: 12pt; font-family: serif;"> </span></i></div><div style="margin: 0in 0in 0.0001pt; font-size:
11pt; font-family: Calibri,sans-serif;"><span style="font-size: 12pt; font-family: serif;">I am on a short trip in Florida and away from my code books. Can someone provide guidance and code reference please? I am concerned about the 20 foot distance of the un-protected circuit from the supply side tap and also the interrupt rating of the 60 Amp breaker in the Xantrex distribution panel.</span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"> </div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;">David Palumbo</div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;">Independent Power LLC</div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;">Offices in Lamoille and the Champlain Valley</div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family:
Calibri,sans-serif;">802.888.7194</div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><a rel="nofollow" target="_blank" href="http://www.independentpowerllc.com/" style="color: blue; text-decoration: underline;">www.independentpowerllc.com</a></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri,sans-serif;"><font class="Apple-style-span" face="Helvetica"><span class="Apple-style-span" style="font-size: medium;"><font class="Apple-style-span" face="Calibri, sans-serif" size="4"><span class="Apple-style-span" style="font-size: 15px;"><br></span></font></span></font></div></div></div></span></div></div></div>_______________________________________________<br>List sponsored by Home Power magazine<br><br>List Address: <a rel="nofollow" ymailto="mailto:RE-wrenches@lists.re-wrenches.org" target="_blank"
href="/mc/compose?to=RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br><br>Options & settings:<br><a rel="nofollow" target="_blank" href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br><br>List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org<br><br>List rules & etiquette:<br>www.re-wrenches.org/etiquette.htm<br><br>Check out participant bios:<br>www.members.re-wrenches.org<br><br></blockquote></div><br></div></div><br>-----Inline Attachment Follows-----<br><br><div class="plainMail">_______________________________________________<br>List sponsored by Home Power magazine<br><br>List Address: <a ymailto="mailto:RE-wrenches@lists.re-wrenches.org" href="/mc/compose?to=RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br><br>Options & settings:<br><a
href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" target="_blank">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br><br>List-Archive: <a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" target="_blank">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br><br>List rules & etiquette:<br>www.re-wrenches.org/etiquette.htm<br><br>Check out participant bios:<br>www.members.re-wrenches.org<br><br></div></blockquote></td></tr></table><br>