The AHJ generally enforces the code, which specifically allows loading a busbar with 120% of its rating when backfeeding solar into it. So it depends on what you define as "correct". Following the code, or following the laws of physics. I hate to admit it, but there are many things in the code that are not based on the laws of physics. I've been doing solar for 25+ years now, and also know a bunch of people on code writing panels, and have learned that writing the code is much like writing legislation, lots of special interests and political lobbying -- it's not just a bunch of engineers or physicists sitting around deciding what is the safest way to build something.
On Sun, Mar 10, 2024 at 10:57 PM Lawrence Winiarski via EV < ev@lists.evdl.org> wrote: > My AHJ nor my brothers did not enforce it so we've had a different > experience. > > > On Sunday, March 10, 2024 at 10:45:01 PM PDT, (-Phil-) < > p...@ingineerix.com> wrote: > > The NEC definitely accounts for this since 2011, and I know from > experience AHJs enforce it. (705.12 D 2) > > There are 2 ways:1. Derate: Replace the main with a lower amperage, or:2. > End Feed: Install the solar breaker at the opposite end of the busbars and > put a sign that states: "SOLAR PV BREAKER - BREAKER IS BACKFED, DO NOT > RELOCATE!" > Most brands of panels also now over-rate the busbars for this reason on at > least some of their models. > > On Sun, Mar 10, 2024 at 9:52 PM Lawrence Winiarski < > lawrence_winiar...@yahoo.com> wrote: > > I'm going to chime in with a point. Probably plenty all ready know it, > but maybe some don't. > Virtually all home solar is actually kind of technically violating some > electrical rules. The reason is thatbreakers were not intended to be used > to back feed power, but that is the easiest way, so the code peopleactually > look the other way. > > The problem is as follows. > Imagine a 200 amp panel for you house. It has a big 200 amp breaker at > the top and the bus bars are designed to handle 200 amps.Further imagine > that you have a 40 amp solar. > So imagine you have no solar (it's dark) and you turn on every appliance > and you are drawing 200 amps. (or a tiny bit less). No problem as the > main breaker (the 200amp one) doesn't flip yet. Now turn on the 40 > amps of solar and now the main breaker is only seeing 160 amps (160 from > the power company and 40 from the solar is going into your appliances. > But the important thing is the bus bars are still seeing (or potentially > seeing 200 amps). Now start charging your EV (say it's 40 amps) so > now the bus bars are seeing 240 amps and the main breaker STILL doesn't > flip (because it's now it only sees 200 amps. > So you are technically over powering the panel bus bars more than they are > rated for. > The proper solution is actually to put in a NEW main breaker of 160 amps > but almost nobody does that. > > But the reality is the code people fudge it and allow 20% but it's not > really correct. > Anyway I'm guessing this has something to do with your adding outlets to a > solar panel not being entirely kosher. > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20240311/dc15b180/attachment.htm > > > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20240311/2205efaa/attachment.htm> _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
