Larry,

Would it not be better to connect the Honda directly to the the Sunny Islands?
Use a manual transfer switch to choose between the grid and the Honda. Then, in
an extended outage, your client could charge the batteries with it and turn the
darn thing off once in awhile. Maybe you could transfer more of the loads to the
backup panel. How big is the Honda? I don't know of one bigger than 10KW. That's
too small to support a busy 200 Amp panel anyway.

Dick Ratico
Solarwind Electric


--- You wrote:
> 
> Wrenches,
> 
> I have a client with a 4.6 kw grid tied system using a Sunny Boy 6000
inverter.  We have AC Coupled to that system with 2 Sunny Island 5048's and
8-Concorde SunXtender 3050T 6 volt batteries in series feeding an essential
load/critical load sub panel.  The wiring to the sub panel from the Sunny
Islands is #6, the max wire size that can be used in the AC 1 and AC 2, in and
out, of the Sunny Islands.  The 2 pole breaker at the sub panel is 70 amps ( 56
amps feed through current x 1.25 = 70 amps ).
> This allow the 4.6 kw solar system and the Sunny Boy 6000 to act as a micro
grid and charge the batteries and support the loads in the SubPanel when the
grid is down and still be isolated from the main service panel and the grid. 
> 
> We have moved several loads from the main 200 amp service panel into the
essential load/critical load panel, the well pump, the refrigerator, the
circulator/boiler controls for the propane fired radiant heating system and some
lights and communication circuits.  
> 
> The main 200 amp main service panel has an integrated manual transfer switch
that has allowed them to fire up the gas powered Honda generator and run all of
the loads when the grid was down before we installed any systems to their home. 
They would like to be able to continue to do this in an extended power outage.
> 
> So here is the question?  In a power outage, if they fire up the generator and
move the manual transfer switch in the Main Service Panel to generator, the
Sunny Islands will see this generator power coming from the Main Service Panel
and switch from Back Up Mode to Pass Through Mode.  The Sunny Boy 6000 will send
any excess power not used by the loads to the the generator (as if it was a net
metering arrangement ) believing it is the grid. This would probably destroy the
generator or some other disasterous scenario.  
> 
> So how can the generator feeding the Main Service panel be isolated from the
Sunny Islands and Sunny Boy feeding the SubPanel as a micro grid in a power
outage and still provide power to the loads that are in the Main Service Panel?
> 
> Thank you for the collective wisdom and knowledge that this group has acquired
from years in the trenches making it all happen.
> 
> Larry
> 
> Larry Brown
> Sun Mountain
> NABCEP Certified PV Installer
> 
--- end of quote ---

