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 that > breakers were not intended to be used to back feed power, but that is the > easiest way, so the code people > actually 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/20240310/28223dc9/attachment.htm> _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
