Good Morning Wrenches,
I'm wondering if anyone has an advice on preferred methods and
component/panel recommendations for paralleling multiple inverters. The
proposed system will utilize 4 SMA6000 inverters (100 amps) and will be a
ground mounted system with inverters located outdoors in the cold
Hi Rich
If there are no AC loads, only the inverters then there is no derate for the
panel buss.
However if you connect any other loads such as a metering device, now you have
to apply the 120% rule.
Jay
Peltz Power
On Jan 22, 2012, at 4:53 AM, Rich Nicol r...@solartechvt.com wrote:
That is very interesting Jay, do you have a code reference for no derate needed
for your solar accumulation panel?
Thanks,
Nick Vida
btw- Rich, thanks for Bernie Sanders.___
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Nick,
Forgive me as I am referencing NEC 2008. But 690.64 (B) Load Side, ...and
where this distribution equipment is capable of supplying multiple branch
circuits, or feeders, or both...shall comply...
To the extent the accumulation panel is NOT capable of supplying other
circuits, then NONE
Hi Nick,
I see (2011) 705.12 (d) where it talks about supplying branch circuits as
the area where it changes.
ie w/o branch circuits then all circuits are protected by the breakers as long
as the main buss isn't exceeded by the solar input of course.
But in putting in that metering device
Rich:
Here is the first consideration you might want to make: You state a value
of 100 Amps for this system, which I assume is the maximum AC output at 240
VAC (25 Amps) times four inverters. The value of 25 amps per inverter is
irrelevant to your design, however. You must take the 25 amps
William,
The SMA6000 @ 240V has an AC output rating of 25A. 4 times 25 times 1.25
equals 125 A. If the solar accumulation panel is a dedicated load center,
then the load center, feeder and feeder breaker need only be rated to 125 A.
If the dedicated load center is located in the same building as
Friends:
I have heard, but I have not researched myself, a provision in the code
where one could dedicate a panel to be an AC combiner to collect the
outputs of multiple inverters. You would not install any branch circuit
breakers and thereby eliminate the need to comply with the 120% rule.
Jay:
Thanks for citing this section. I reviewed it just now (2008 version) and
I noticed that it says, capable of supplying multiple branch
circuits, not actually supplying branch circuits. Any energized
breaker panel is capable of supplying branch circuits. Only if you size
the panel
Mark:
I would respectfully disagree, based on my reading. If you have code
citations that inform me otherwise, I would be very grateful to expand my
knowledge.
Pending hearing otherwise from you, here is what I know, based on 2008
code, and assuming load side connection (2008 citations in
William,
I think we have it all out on the table. Below you cite 2008 690.64 (B) (2).
But the requirements of (B) (2) do not come into play if it is excluded by
the provisions of 690.64 (B). And as you already pointed out, this all
revolves around the interpretation of the Code vis-a-vis the
Wrenches
Thanks for the detailed responses.
My understanding is the same as William's that my total back feed value is
based on the over current devices for each inverter which is 40 amps X 4 =
160 Amps.
Where I'm having a problem is choosing a panel based in respect to
considering both the
Rich,
If you have an archive of Wrenches email, also see thread on this subject
dating on and about March 29, 2011.
Mark Frye
Berkeley Solar Electric Systems
303 Redbud Way
Nevada City, CA 95959
(530) 401-8024
http://www.berkeleysolar.com/ www.berkeleysolar.com
_
From:
RIch;
I think you're exactly right on your interpretation. Mike Holt's
Guide to 2011 NEC requirements for PV... has an 'author's comment' on
page 305, that the 120% buss bar rule of article 705 only applies if
there are loads in the panel. If all slots are filled with PV breakers,
you're
Mark:
Thank you.
William
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I am a little late on this:
Mark and Jay,
thanks for the code reference for the solar accumulation panel bus rating. It
is too bad that adding a little 15 amp receptacle for your monitoring that
draws like 7 watts is enough to incite a derate under the more optimistic
school of thought.
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