Here is the corrected drawing for the record.
On Sun, Nov 8, 2020 at 12:51 PM Jason Szumlanski < [email protected]> wrote: > Correction... The PV OCPD would need to be 80A or less or the total loads > would need to be 100A or less. It's the sum of the OCPD, not loads plus > rated PV current. > > On Sun, Nov 8, 2020, 12:46 PM Jason Szumlanski < > [email protected]> wrote: > >> It's a 200A bus. >> >> 300A "on" the bus doesn't matter. The total of all load and supply >> devices does not exceed the bus rating. This is 705.12(D)(2)(3)(c) in >> 2014/2017. >> >> In no way can the total ampacity on the 200A bus exceed 200A as long as >> additional loads are not added, hence the required warning label. Where >> would 300A of current ever flow? >> >> On Sun, Nov 8, 2020, 12:30 PM Jay <[email protected]> wrote: >> >>> Hi Jason >>> >>> My question is if it’s 200a in from the main breaker and 100a from PV >>> its 300 amps on the buss correct? >>> >>> How is that ok with the 125% rule? >>> >>> Or is this covered by some other rule as it’s a feed through lug load >>> center? >>> >>> Jay >>> >>> >>> >>> On Nov 8, 2020, at 9:46 AM, Jason Szumlanski < >>> [email protected]> wrote: >>> >>> >>> 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. >>> >>> 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. >>> >>> 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. >>> >>> Jason Szumlanski >>> >>> >>> >>> >>> >>> On Wed, Oct 28, 2020 at 5:15 PM Jason Szumlanski < >>> [email protected]> 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 < >>>> [email protected]> 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 <[email protected]> >>>>> 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/6eb0c6c8006878ded7b952fd907cf2296d8a8c23?url=http%3A%2F%2Fwww.solarenergy.org&userId=1613865&signature=b90b1c342f944fc6> >>>>>> >>>>>> SEI Professional Services >>>>>> http://www.seisolarpros.com >>>>>> <https://mailtrack.io/trace/link/0c7a06ede90529e40edf3310fc409ef25d314f50?url=http%3A%2F%2Fwww.seisolarpros.com&userId=1613865&signature=90f78f85b5245d83> >>>>>> >>>>>> >>>>>> >>>>>> On Wed, Oct 28, 2020 at 10:18 AM Jason Szumlanski < >>>>>> [email protected]> 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 >>>>>>> >>>>>> <Feed Through Lug Interconnection Option (2).pdf> >>> _______________________________________________ >>> List sponsored by Redwood Alliance >>> >>> List Address: [email protected] >>> >>> Change listserver email address & settings: >>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>> <https://mailtrack.io/trace/link/a508814a91f7fad4c91cb6fc97922e45ccd78e16?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=42daadc1cf7c9084> >>> >>> There are two list archives for searching. When one doesn't work, try >>> the other: >>> https://www.mail-archive.com/[email protected]/ >>> <https://mailtrack.io/trace/link/1f9850889dc692a09d33ffb9c74141df66c2f619?url=https%3A%2F%2Fwww.mail-archive.com%2Fre-wrenches%40lists.re-wrenches.org%2F&userId=1613865&signature=d673e951847c87eb> >>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >>> <https://mailtrack.io/trace/link/43f4b3a8fe61bd04fcc0da80189644cd4469af0e?url=http%3A%2F%2Flists.re-wrenches.org%2Fpipermail%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=4aba6be7c097c677> >>> >>> List rules & etiquette: >>> http://www.re-wrenches.org/etiquette.htm >>> <https://mailtrack.io/trace/link/8b9d34a3cd498671f1ffd693900413a452386135?url=http%3A%2F%2Fwww.re-wrenches.org%2Fetiquette.htm&userId=1613865&signature=c808e1d55c0af1a3> >>> >>> Check out or update participant bios: >>> http://www.members.re-wrenches.org >>> <https://mailtrack.io/trace/link/04218d8e6a1baae12f88b2d657e2f45e9f798c4e?url=http%3A%2F%2Fwww.members.re-wrenches.org&userId=1613865&signature=545fb4d0ff21ff33> >>> >>> _______________________________________________ >>> List sponsored by Redwood Alliance >>> >>> List Address: [email protected] >>> >>> Change listserver email address & settings: >>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>> <https://mailtrack.io/trace/link/6b09aeef26f6788fb5d2ea22112bb686347b7fbf?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=198f8532a8201f02> >>> >>> There are two list archives for searching. When one doesn't work, try >>> the other: >>> https://www.mail-archive.com/[email protected]/ >>> <https://mailtrack.io/trace/link/d2a5dfee8cf90cc9d6d0507dc021f7df79d9a729?url=https%3A%2F%2Fwww.mail-archive.com%2Fre-wrenches%40lists.re-wrenches.org%2F&userId=1613865&signature=4b66bc2ee38a9e73> >>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >>> <https://mailtrack.io/trace/link/bff29ac89287feeed11cf19c6690147803c2d9c3?url=http%3A%2F%2Flists.re-wrenches.org%2Fpipermail%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=fc732945abf29f4e> >>> >>> List rules & etiquette: >>> http://www.re-wrenches.org/etiquette.htm >>> <https://mailtrack.io/trace/link/9c70dbeffa47721f81c73a2a13b61737dfc9ebff?url=http%3A%2F%2Fwww.re-wrenches.org%2Fetiquette.htm&userId=1613865&signature=c045bc78f52658c4> >>> >>> Check out or update participant bios: >>> http://www.members.re-wrenches.org >>> <https://mailtrack.io/trace/link/f342a09c740b61f880b6ca21f6456c58b1e65a97?url=http%3A%2F%2Fwww.members.re-wrenches.org&userId=1613865&signature=fb4c9c552fd1b7a9> >>> >>>
Feed Through Lug Interconnection Option (2)(REV1).pdf
Description: Adobe PDF document
_______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] 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/[email protected]/ 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
