There's no problem with installing the panel and 690.64(B) is the
appropriate section to look at.
"690.64(B)(2) Bus or Conductor Rating. The sum of the ampere ratings of
overcurrent devices in circuits supplying power to a busbar or conductor
shall not exceed 120 percent of the rating of the busbar or conductor."
If you size the panel so that it can accommodate the sum of the
inverters AND the utility side fuse/breaker, then this meets
690.64(B)(2) no problem. For example, if you have 2 30A inverter
breakers and 1 60A fused disconnect as your line side tap, that's
30+30+60A total source that can energize the panel, so a 100A panel
would work here as long as you follow 690.64(B)(7) and have the PV
breakers at the opposite end of the main lugs/breaker.
If what you're trying to do is get away with a 60A panel rather than a
100A panel, that's where you have to get special permission from the
AHJ, and they'd probably require language somewhere along the lines of
"PV circuits only. Do not add load breakers." This system would be safe
if no loads are attached (you can easily see that you wouldn't see more
than 60A flowing across the buses here), but the key is to affix a
permanent label so that no additional breakers are ever added- just in
case the next person along assumes that everything is NEC compliant.
DKC
-------- Original Message --------
Subject: [RE-wrenches] Solar accumulation panel
From: Andrew Truitt <atru...@gmail.com>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Date: 2010/1/12 13:57
Team wrenches - I feel like I've seen a provision in the Code for
installing a sub-panel to aggregate PV inverter outputs for the purpose
of simplifying the actual grid connection (such as for a line-side tap)
but I can't find it in 690. I also seem to remember specific verbiage
that needs to be on the panel along the lines of "PV circuits only. Do
not add load breakers." to ensure compliance with 690.64(B). Does
anyone know where I can find this info in the NEC?
Andrew Truitt
Standard Solar Inc.
--
"Don't get me wrong: I love nuclear energy! It's just that I prefer
fusion to fission. And it just so happens that there's an enormous
fusion reactor safely banked a few million miles from us. It delivers
more than we could ever use in just about 8 minutes. And it's wireless!"
~William McDonough
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