Mac, that Island interconnects with a max 70A 1P breaker (6.7kW
continuous), so unless they have a constant critical load draw or the
Fronius is massively oversized, you probably don't want to AC couple the
Fronius. The 5048 is also able to output a continuous 5000W only when
it's cooler than 77F and it derates above that (4500W at 95F, for
example). I don't believe its surge ratings apply to the AC2 output back
into the utility but they probably wouldn't be enough, anyway. I think
that whenever the Fronius output reached about 6000W, the SI would shift
its frequency to switch the Fronius off. Cheapest may be along the lines
of your first option-- not sure what the PV stringing is like but maybe
you could move a string or two off the Fronius and put it onto a new
Sunny Boy with an autoformer. Since I imagine this system doesn't have
PV WIRE on the module leads or home runs, officially I'd recommend a
classic Sunny Boy. Then leave the Fronius as-is.
Unless of course the customer thought they were buying a system with the
full 10kW supplying critical loads when the utility is down... then the
original contractor is stuck with buying the second SI they should have
installed in the first place.
DKC
On 2014/7/3, 10:46, Mac Lewis wrote:
Hello wrenches,
I wanted to run this scenario by the forum. I have spoken with SMA
about this, but want some other opinions.
We were recently contracted by a fellow solar company to do some
warranty work for them out of town on a Sunny Island system that they
had installed about 5 years ago. It was VERY poorly implemented
originally and was never installed as SMA intended. In fact, during a
small power outage, the only loads that never came back on after the
utility was back on line were the loads in the critical load panel.
Oops.
Anyway, our job is to get it working properly for the least amount of
cost possible. They have a Fronius IG Plus 10.0 fed into a 400A
service panel. The Sunny Island 5048 AC Input also comes off of this
panel and feeding a 120V only critical load panel. Please note that
there is no solar fed into the AC output side of the Sunny Island,
because there is not 120/240 available and thus there is no possible
way for this system to utilize the solar while the grid is not present.
I see two options (but there may be more): pull out Fronius, put in
Sunny Boy inverters and an autoformer, wire properly. Another option
is to add second Sunny Island and try to AC couple the Fronius with
the two Sunny Islands. The second option is less expensive overall,
but I'm hesitant to rely on AC coupling with the Fronius.
I'd appreciate any thoughts on this.
Thanks
--
Mac Lewis
*
"Yo solo sé que no sé nada." -Sócrates
*
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