[RE-wrenches] Fwd: AC Coupled

[JRQ]

Larry,

A Sunny Boy won't feed any power directly at a generator on the main panel: the AC on either side of the Sunny Island is separately derived, and it's my understanding that the SI can command the SBs through the CAT V link to throttle back if loads aren't sufficient. Wouldn't the Sunny Island inverters see that there is no load coming from the AC main panel where the generator is located? I would think the SI should be smart enough not to backfeed power at another source unless it sees a load. I could be wrong about this, though. Call SMA and ask. I think the main SI tech guy for SMA America is Roy Dyngen. Let us know what they say.

Jeffrey Quackenbush
NABCEP Certified PV Installer
Peripatetic Solar Technician


________________________________
 From: Larry Brown <sunmountain at netstep.net>
To: RE-wrenches <RE-wrenches at lists.re-wrenches.org> 
Sent: Saturday, February 18, 2012 9:03 AM
Subject: [RE-wrenches] Fwd: AC Coupled
 

> 
> 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
> 
> 

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