<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"></div><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Maybe this is a better example (attached). I don't see how this would be a problem under NEC 2014, 2017, or 2020. No portion of the main bus, feeder conductors, or subpanel could possibly be subjected to overcurrent without an OCPD stopping it.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">My point is that here we are, 3 code cycles in since feeder taps were addressed, and there is still no clarification of intent. AHJs are still struggling with this. </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I'm not sure where residential meter/mains with feed through lugs are popular. I know they are in Florida and I have heard Hawaii. I'm curious what your jurisdictions think of this if you have this scenario. Most of the time the subpanel is main lug only, but adding a main circuit breaker is usually an easy and cost-effective fix to make this interconnection type work.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Jason Szumlanski</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><b><div style="text-align:center"><br></div></b></div></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Oct 28, 2020 at 5:15 PM Jason Szumlanski <<a href="mailto:jason@floridasolardesigngroup.com">jason@floridasolardesigngroup.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div style="font-family:arial,helvetica,sans-serif"></div><div dir="ltr"><div style="font-family:arial,helvetica,sans-serif">For further discussion, I don't see how my original scenario is any different from this attached scenario, which I think everyone would agree is allowed. All conductors and busbars are subject to the same potential loads and fault currents. </div><div style="font-family:arial,helvetica,sans-serif"> (Image attached).</div><div><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><table border="0" cellpadding="0" cellspacing="0" style="font-family:"helvetica neue",helvetica,arial,sans-serif"><tbody></tbody></table><b><div style="text-align:center"><br></div></b></div></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Oct 28, 2020 at 5:01 PM Jason Szumlanski <<a href="mailto:jason@floridasolardesigngroup.com" target="_blank">jason@floridasolardesigngroup.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div style="font-family:arial,helvetica,sans-serif"></div><div dir="ltr"><div style="font-family:arial,helvetica,sans-serif">Of course the feeder conductors and bus bar could be subjected to a fault. But we're not talking about faults here. Fault protection is the job of the PV OCPD And primary supply OCPD to protect the downstream busbar and feeders. If that wasn't the case, you would need a new OCPD on BOTH the load and line side of a solar connection as a feeder tap, not just the load side.</div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif">If your interpretation is correct regarding the location of the OCPD, that sounds like a sub-feed breaker is the only way to comply, and I haven't seen such an animal for a typical residential load center. You can get these for NQ panelboards and similar panelboards from other manufacturers of course. It doesn't say as close as practicable or anything like that. It says that a busbar connection is allowed when there are feeder CONDUCTORS connected to feed through LUGS. What does "overcurrent device .. <i>at</i> the supply end" mean? I emphasize "at." It's unclear how you would implement this other than a sub-feed breaker I suppose, but that's not what it says. It refers to feeder conductors on lugs on busbars, not feeder conductors on load-side terminals of an overcurrent device.</div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif"></div><div style="font-family:arial,helvetica,sans-serif">My point is that 705.12 should have been wrapped up neatly in a bow, but the lack of clarity, still, is astonishing. Why add a section about feed-through lugs if it's going to be so vague?<br></div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif">Jason</div><div><span style="font-family:Arial,Helvetica,sans-serif"></span></div><div style="font-family:arial,helvetica,sans-serif"><br></div><div><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><table border="0" cellpadding="0" cellspacing="0" style="font-family:"helvetica neue",helvetica,arial,sans-serif"><tbody></tbody></table><b><div style="text-align:center"><br></div></b></div></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Oct 28, 2020 at 3:37 PM Brian Mehalic <<a href="mailto:brian@solarenergy.org" target="_blank">brian@solarenergy.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Hey Jason, <div>Here's the 2020 text:</div><div><br></div><div>
<p style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;font-family:"Helvetica Neue Light";color:rgb(0,0,0)">6)<span style="white-space:pre-wrap"> </span> Connections shall be permitted on busbars of panelboards that supply lugs connected to feed-through conductors. The feed-through conductors shall be sized in accordance with 705.12(B)(1). Where an overcurrent device is installed at the supply end of the feed-through conductors, the busbar in the supplying panelboard shall be permitted to be sized in accordance with 705.12(B)\u2060(3)\u2060(1) through 705.12(B)(3)(3).</p><p style="margin:0px;font-variant-numeric:normal;font-variant-east-asian:normal;font-stretch:normal;line-height:normal;font-family:"Helvetica Neue Light";color:rgb(0,0,0)"><br></p><div><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>The OCPD on the supply end of the feed-through conductors would be in the form of a sub-feed breaker at the point of supply to those conductors, re-establishing overcurrent protection of the conductors (likely at the same ampacity as the main breaker in the supplying panel. The feed-through conductors are basically an extension of the busbar in the supplying panel; they can either be protected by the main, or in the presence of multiple sources of power in the supplying panel (such as a backfed PV system breaker) they can be protected based on (B)(3)(1) - "the 125% rule" - or they can be protected by a new overcurrent device at their point of supply, in which case current on them is limited based on that OCPD size; in this latter scenario the busbar in the supplying panel is allowed to be sized based on one of (B)(3)(1) - (3) because it is protected downstream at its end.</div><div><br></div><div>The theory is pretty much the same as 705.12(B)(1) for feeders - when not connecting at the end of the feeder, use the "125% rule" or re-establish overcurrent protection for that portion of the feeder subject to multiple power sources.</div><div><br></div><div>In your drawing the 200 A feeder conductors, as well as the busbar below the PV system breaker, could be subject to > 200 A in the event of a fault somewhere along those conductors. </div><div><br></div><div>Brian Mehalic <br>NABCEP Certified Solar PV Installation Professional\u2122 R031508-59</div><div>National Electrical Code® CMP-4 Member</div><div>(520) 204-6639<br><div><br></div><div><div><div>Solar Energy International<br><a href="https://mailtrack.io/trace/link/b21acbbeee09b823ad85f3914f3c4e6948b3ed61?url=http%3A%2F%2Fwww.solarenergy.org&userId=1613865&signature=8ec85587a9fbe44e" target="_blank">http://www.solarenergy.org</a></div></div></div></div><div><br></div><div>SEI Professional Services</div><div><a href="https://mailtrack.io/trace/link/16ff4b9d2b5a9ff30e778067c7a9f70657f436ad?url=http%3A%2F%2Fwww.seisolarpros.com&userId=1613865&signature=c8818c380f4375fb" target="_blank"><span style="font-size:12.8px">http://www.s</span>eisolarpros.com</a><br></div><div><br></div></div></div></div></div></div></div></div></div></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Oct 28, 2020 at 10:18 AM Jason Szumlanski <<a href="mailto:jason@floridasolardesigngroup.com" target="_blank">jason@floridasolardesigngroup.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div style="font-family:arial,helvetica,sans-serif"></div><div style="font-family:arial,helvetica,sans-serif">Does anyone else think they botched the wording in this section? It's still not clear, and we have a ton of meter/main combos with feed-through lugs around here.</div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif">Where is it written, "where an overcurrent device is installed at the <b><i>supply end</i></b> of the feed-through conductors," (emphasis added) are they referring to the solar backfed breaker on the busbar or another breaker somewhere along the feeder circuit? It goes on to state that the loads on the supplying busbar can comply with any method in 705.12(B)(3), which prescribes an OCPD at the load end of the feeder in 705.12(B)(3)(3), so they can't be talking about that. I have to assume it is the solar backfed breaker they are referencing.</div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif">See my interpretation of one scenario in the attached image. </div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif">We're a long way off from the 2020 code implementation here, but it can help sway plans examiners looking to clarify the intent of the 2014/2017 code cycles.</div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif"><br></div><div style="font-family:arial,helvetica,sans-serif">Jason Szumlanski</div></div></blockquote></div>
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