I'm not following you. How is this not at the end of the feeder? The feeder terminates at the main breaker in the subpanel.
On Wed, Oct 28, 2020, 6:34 PM Brian Mehalic <br...@solarenergy.org> wrote: > This scenario is certainly allowed, but since it's not at the end of the > feeder, either: > > 1. a. > > The feeder ampacity shall be not less than the sum of the primary > source overcurrent device and 125 percent of the power-source output > circuit current. > 2. b. > > An overcurrent device at the load side of the power source connection > point shall be rated not greater than the ampacity of the feeder. > > As with the feed-thru conductors, the idea is make them big enough or > re-establish overcurrent protection, and protect busbars accordingly. > > > > > Brian Mehalic > NABCEP Certified Solar PV Installation Professional™ R031508-59 > National Electrical Code® CMP-4 Member > (520) 204-6639 > > Solar Energy International > http://www.solarenergy.org > > SEI Professional Services > http://www.seisolarpros.com > > > > On Wed, Oct 28, 2020 at 2:48 PM Jason Szumlanski < > ja...@floridasolardesigngroup.com> wrote: > >> 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. >> (Image attached). >> >> >> >> On Wed, Oct 28, 2020 at 5:01 PM Jason Szumlanski < >> ja...@floridasolardesigngroup.com> wrote: >> >>> 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. >>> >>> 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 .. *at* 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. >>> >>> 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? >>> >>> Jason >>> >>> >>> >>> >>> On Wed, Oct 28, 2020 at 3:37 PM Brian Mehalic <br...@solarenergy.org> >>> wrote: >>> >>>> Hey Jason, >>>> Here's the 2020 text: >>>> >>>> 6) 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)(3)(1) through 705.12(B)(3)(3). >>>> >>>> >>>> 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. >>>> >>>> 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. >>>> >>>> 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. >>>> >>>> Brian Mehalic >>>> NABCEP Certified Solar PV Installation Professional™ R031508-59 >>>> National Electrical Code® CMP-4 Member >>>> (520) 204-6639 >>>> >>>> Solar Energy International >>>> http://www.solarenergy.org >>>> <https://mailtrack.io/trace/link/6861d7d8805b342c05a1945424d5d3679153b6c2?url=http%3A%2F%2Fwww.solarenergy.org&userId=1613865&signature=755f4d3125876434> >>>> >>>> SEI Professional Services >>>> http://www.seisolarpros.com >>>> <https://mailtrack.io/trace/link/56a599fdf28222e003dcf7711461480ee5165051?url=http%3A%2F%2Fwww.seisolarpros.com&userId=1613865&signature=68c217cadacd349b> >>>> >>>> >>>> >>>> On Wed, Oct 28, 2020 at 10:18 AM Jason Szumlanski < >>>> ja...@floridasolardesigngroup.com> wrote: >>>> >>>>> 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. >>>>> >>>>> Where is it written, "where an overcurrent device is installed at the >>>>> *supply >>>>> end* 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. >>>>> >>>>> See my interpretation of one scenario in the attached image. >>>>> >>>>> 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. >>>>> >>>>> >>>>> Jason Szumlanski >>>>> >>>> _______________________________________________ >> List sponsored by Redwood Alliance >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> There are two list archives for searching. When one doesn't work, try the >> other: >> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org >> >> _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > >
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