Sunny Island Retrofit [RE-wrenches]

[John Berdner]

August/Wrenches:
 
I suggest a bypass switch in all backup power / off grid with generator
installations.  
This has little to do with inverter choice.
I like bypass switches because there is a simple way to get things up
an running immediately while you sort out what went wrong.
I believe the benefit of having a simple way to transfer the critical
loads to the grid or generator outweighs the added costs.
You can use an unfused manual transfer switch which are pretty
reasonable from several different suppliers.
 
You can notify the customer of a grid outage using the one the two
programmable relays in each 5048U.
One of the functions can be to close / open when the grid is present /
absent.
You have access to the NC, COM, and NO terminals so you can invert
logic where needed.
The SI5048U also has battery voltage (48 Vdc) excitation terminals (750
mA max) inside the unit for driving other relays, indicator lights,
buzzers, etc. 
You can also use the grid present to activate an external automatic
transfer switch so that the big protected loads are powered directly by
the grid when it is there.
 
The SI5048U is rated a 5000 Watts continuous @ 25C but can do
substantially more for short periods of time.  It can output 6500 Watts
for 30 minutes (many older inverters used this 30 minute rating as the
power rating) and 7200 Watts for 5 minutes so a hard 5000 Watt limit may
be overly conservative.  The only other concern I would have is the 25
Amp breaker limit on the Outback autoformer. Based on your description
of the large number of protected loads the 25 Amp breaker may not be
enough.  With a pair of SI5048's you use a 70 Amp breaker on each unit
which almost triples the available pass through current.  
 
Best Regards,
 
John Berdner

>>> August at luminalt.com 11/8/2007 08:09:11 AM >>>


Wrenches -

I'm looking for help in figuring out a dilemma for a Sunny Island
grid-connected system with battery backup. 

We are upgrading an old Trace grid-connected battery backup system to a
new
Sunny Island based system. We just fired up the Sunny Island 5048U
yesderday
along with a SB 7000US and and SB 4000US (attached to a 9 kW PV
array).
Everything went well and I'm pleased with the general operation; the
new
Sunny Island has a very intuitive interface. We're using an IOTA
transfer
switch to allow the Sunny Boys to bypass the Sunny Island and Outback
X240
autoformer to reduce losses.

The problem is that the client has a huge quantity of critical loads.
I
didn't realize this at first. Most of them are 120 Volt but a few are
240
Volt. There are four critical loads sub panels and it seems like 80% of
the
day to day loads are connected though these critical panels. Another
contractor installed these years ago so we didn't have any control over
this
portion of the design. It's a bit crazy. The sunny island operates such
that
all of the critical loads run through the Sunny Island and Outback
autoformer. If the Sunny Island and/or autoformer fail then the
critical
panels will also shut down. I'm considering recommending adding a
second
Sunny Island which will eliminate the autoformer and add an additional
5000
Watts of critical load ability. Secondly, I'd like to add a transfer
switch
to bypass the Sunny Islands incase they fail.

We've warned the customer that their critical loads can never exceed
5000
Watts and that during a power outage they will drastically need to
reduce
their usage. A point that came up, however, is that they probably won't
even
know if the power does go down. The Sunny Island switches over to
battery
backup completely seamlessly. 

My questions:

1. Does anyone have experience and or recommendations about a better
way to
setup this system?

2. Does anyone have experience with the reliability of the above
mentioned
products?

3. Does anyone have suggestions for notifying the customer if/when the
power
goes down so that they can start conserving?

Any other comments are welcome. 

Thanks, August

August Goers
VP, Engineering
NABCEP Certified PV Installer R

Luminalt Energy Corporation
Office: (415) 564-7652
Mobile: (415) 559-1525
www.luminalt.com 
august at luminalt.com 


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