We always specify a smaller neutral for Enphase IQ systems with 240V output where the feeder neutral is only used for the Envoy data monitor. I have never experienced a problem with an AHJ. However, this is not based on Article 705. It's based on 220.61.
I just note why the neutral is downsized on the plans with the code reference. Technically it can go all the way down to #14 neutral to supply the 15A circuit for the Envoy data monitor, but we typically use #10 or the EGC size, whichever is larger. The circuit from a breaker in the main panel to an AC combiner load center is a feeder, so 220.61 applies. It also applies in the case of a supply-side connection from the fusible disconnect and then continuing on to an AC combining load center. If you are talking about a branch circuit to an inverter, that isn't a feeder, so that's probably going to be a different story. 705.95 could apply depending on what the neutral is needed for. If it's strictly for voltage sensing or data comm, that might work. Of course, if the PV AC Combiner has other loads, the feeder neutral needs to be sized to handle these loads as well. This can be the case where we are not using the Enphase IQ Combiner, but it's rare for us since we usually dedicate a load center for PV AC combining only and exclude all other loads. Jason Szumlanski Florida Solar Design Group On Thu, May 7, 2020 at 11:04 AM Al Frishman <[email protected]> wrote: > Hey Wrenchers, > Wondering what you all think about NEC Article 705.95 and if downsizing > the Neutral is common practice. If your JHA accepts it and the model > inverter you are installing complies do you see any issues with downsizing > the Neutral? This section of code has been in place since 2011 and I must > admit I have been slow to adopt it. > > 705.95 Ampacity of Neutral Conductor. The ampacity of the neutral > conductors shall comply with either (A) or (B) > (A) Neutral Conductor for Single Phase, 2-Wire In- verter Output. If a > single-phase, 2-wire inverter output is connected to the neutral and one > ungrounded conductor (only) of a 3-wire system or of a 3-phase, 4-wire, > wye- connected system, the maximum load connected between the neutral and > any one ungrounded conductor plus the inverter output rating shall not > exceed the ampacity of the neutral conductor. > > (B) Neutral Conductor for Instrumentation, Voltage Detection or Phase > Detection. A conductor used solely for instrumentation, voltage > detection, or phase detection and connected to a single-phase or 3-phase > utility-interactive inverter, shall be permitted to be sized at less than > the ampacity of the other current-carrying conductors and shall be sized > equal to or larger than the equipment grounding conductor. > > *Al Frishman* > EvolvedSolar > (917) 699-6641 > > _______________________________________________ > 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/4fc2d44617016caf2754cb7685e73e06cbb319d4?url=http%3A%2F%2Flists.re-wrenches.org%2Foptions.cgi%2Fre-wrenches-re-wrenches.org&userId=1613865&signature=f1089370b62be9c9> > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > <https://mailtrack.io/trace/link/a9b5f81025be49ffe4d5281fa9653a493680ba13?url=http%3A%2F%2Fwww.mail-archive.com%2Fre-wrenches%40lists.re-wrenches.org%2Fmaillist.html&userId=1613865&signature=0dc7e1e62f79d4f6> > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > <https://mailtrack.io/trace/link/b22e3e1c5a8228764ce84f087341e0003b619bd7?url=http%3A%2F%2Fwww.re-wrenches.org%2Fetiquette.htm&userId=1613865&signature=1aef36d39ddca7a3> > > Check out or update participant bios: > www.members.re-wrenches.org > <https://mailtrack.io/trace/link/e64c7b45a5756a0d5c061f98d936bd0a9f5fd567?url=http%3A%2F%2Fwww.members.re-wrenches.org&userId=1613865&signature=bd9b160657f9216f> > >
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