[RE-wrenches] More on AC coupling

[Matt Tritt]

I am curious as to why OutBacks were used for this system instead of 
using SunnyIslands and SunnyBoys? From what I can tell about the SI 
system, virtually no aspect of battery charging, auto gen-start/stop, 
and interactive inverter control has been overlooked - or remains to be 
engineered in the field by the installer. Because SunnyIslands have the 
ability to "talk" to Sunny (or Windy)Boys, excess energy is taken care 
of by "integrated load shedding" - no need for multiple relays, dumpoads 
and voltage sensors. :-) The only limitation to these systems (and only 
in 60 Hz land) is a maximum of 20 kW single, and 15 kW three phase per 
autonomous load. I really like the flexibility of being able to connect 
all AC inputs on the same line, as well as having the option to do 
direct battery charging from a DC source (as long as you use a shunt to 
measure current).

I know this doesn't answer your questions, but for similar applications 
in the future it would be good to take a close look at the SunnyIsland 
system. They're cool.



Matt T

Mark Dickson wrote:

> Hello Wrenches,
>
> On the heels of the previous thread:
>
> We just got finished installing a system that utilizes an Outback Quad 
> stack and a 5.2kW array coupled to the AC panel via a Fronius 
> IG5100--due to a long home-run.  The VFX's are wired into the home in 
> their traditional manner, providing the "grid" for the Fronius.  As 
> the solar comes in, excess power not used in the home back feeds the 
> batteries through the VFX's.  I have a series of relays operating dump 
> loads and finally a power cut-off for when the batteries reach 
> critical level.  We installed the system yesterday and turned it on 
> for a test run (then back off to power it up in 2009 for the 
> ITC's)--it worked great!
>
>  
>
> I have a couple questions for you all:
>
>     * Seems how we are back feeding the inverters and forfeiting their
>       charge control, where would you set the dump loads to kick on?
>           o For now I have them set at: 1^st load to kick on at float
>             voltages, 2^nd to kick on at bulk voltages and 3^rd to
>             kick the solar power off at the EQ voltages.  Does this
>             make sense?  The bank is made up of Rolls 4ks-25ps batteries.
>     * Following a recent discussion on the Wrenches list with a
>       similar system:  Do I need to worry about back feeding the
>       generator if it is runnin in the morning when the sun comes up? 
>       Do I need a relay that will shut it down when solar comes on line?
>     * I plan on setting the Absorb and Float set times to a miimum. 
>       Would you recommend this?
>
>  
>
> Thanks for your input!
>
>  
>
> Mark Dickson
>
> Oasis Montana Inc.
>
>  
>
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