[RE-wrenches] Sunny Island retrofit

[Dave Click]

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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