[RE-wrenches] Sunny Island retrofit

Thu Jul 3 22:18:12 PDT 2014

A 60 amp continuously rated AC breaker is what is actually being used in 
the UL listed E Panel from Midnite.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 7/3/2014 9:01 PM, Brian Teitelbaum wrote:
>
> Mac,
>
> Be careful with breaker sizing here. The transfer switch in the SMA 
> SI5048 is only rated for 56A at 120 VAC. From the SI manual:
>
> "The maximum input current allowed on the Sunny Island is 56 A. Higher 
> input currents must not be connected to the Sunny Island."
>
> To protect that switch properly, you would need to use a 50A breaker 
> (unless you can find a 55A breaker that fits in your AC panel). Since 
> most common AC breakers are only rated for 80% duty, you would need to 
> limit that 50A breaker to a continuous 40A load. That's more than the 
> max output current of the Fronius 10.0-1, although it's debatable that 
> the output of a PV inverter is "continuous". It certainly could be in 
> some situations, especially with a tracker mount, although even with a 
> fixed array, you could see max rated output for at least a couple of 
> hours per day.
>
> I agree with the suggestion of putting part of the PV array on a 5kW 
> Sunny Boy, or adding a second Sunny Island and using two Sunny Boy 
> 5000's. Using two Islands would eliminate the need for a transformer, 
> and allow for full array power during grid outages.
>
> Brian Teitelbaum
>
> AEE Solar
>
> *From:*RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org 
> <mailto:re-wrenches-bounces at lists.re-wrenches.org>] *On Behalf Of *Mac 
> Lewis
> *Sent:* Thursday, July 03, 2014 9:34 AM
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] Sunny Island retrofit
>
> 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 
> <mailto: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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