First, breakers themselves really don't care which way the power is
flowing. I can't think of anything about a breaker that would behave
differently if the power flows in or out of the bus bars.
VERY large breakers need power on the input side to rewind the trip
mechanism. Even then, you simply must rewind them with the manual crank
if you are in a no power situation. (You can't reset them if they aren't
rewound.) Aside from that, they also don't care which way the power flows.
I can't recall ever seeing a bus bar overheat due to overloading. I
suspect that the bus bars can take far more than the main breaker
current. Keep in mind that temperature is the issue. The ohmic heating
and the ambient temperature must cause the bus bar to rise to the point
where the insulation will be damaged. Each breaker that you attach to
the bus bar will both draw more current (perhaps) but will also help
wick heat away from the bus bar.
I suppose where you place the solar breaker in the panel might matter,
somewhat. It would likely be best if you placed the solar breaker on the
far end, away from the main breaker. Thus, no portion of the bus bar
would be subject to more amps than the main breaker current. (Think
about this for a moment or two.)
Even if you were to put the solar breaker in the middle of the panel,
the bus bars are not very likely to see a load greater than the main
breaker current, because the circuits between the solar breaker and the
main are drawing current. This draw is likely to be more than the solar
breaker is supplying to the panel. Typically (but not always) it is
general practice to install the larger current breakers near the top of
the panel, near the main breaker.
I would guess that under any normal circumstances, the odds of a bus
bar over load are vanishingly small, particularly if you don't place the
solar breaker near the very top of the panel.
Bill D.
On 3/11/2024 5:52 PM, Lawrence Winiarski via EV 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/20240311/6489e531/attachment.htm>
_______________________________________________
Address messages to ev@lists.evdl.org
No other addresses in TO and CC fields
HELP: http://www.evdl.org/help/
_______________________________________________
Address messages to ev@lists.evdl.org
No other addresses in TO and CC fields
HELP: http://www.evdl.org/help/
