[RE-wrenches] Sunny Island retrofit

[Mac Lewis]

Hi Wrenches,

Jerry, I think you are correct, sma gear all around would be best.  This
will be my recommendation but I am sensitive to this substantial cost.
Dave, if I add the second Sunny Island, I don't think I will be throttled
back because the transfer relays are rated for 60A.  This should pass the
full current of the output of the Fronius, which is 41.7A.  My concern is
more during backup mode, if the Sunny Islands could "trick" the Fronius
into staying on line.  I would add either load dump relay control or an AC
interrupt relay to knock the Fronius off-line if the batteries were full,
in addition to the frequency shift control that the Sunny Island offers.

Thanks for the input, I'll shoot for all SMA gear.

Thanks


On Thu, Jul 3, 2014 at 9:23 AM, Dave Click <daveclick at fsec.ucf.edu> wrote:

>  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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-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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