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 <[email protected]>
To: RE-wrenches <[email protected]>
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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