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:[email protected]
<mailto:[email protected]>] *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 <[email protected]
<mailto:[email protected]>> 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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"Yo solo sé que no sé nada." *-Sócrates***
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