[RE-wrenches] AC Coupled

[Hilton Dier III]

Larry,

I have run into similar situations. The simplest thing is to wire the 
Sunny Boy 6000 into a breaker in a small dedicated box on the *grid 
side* of the transfer switch.

Grid present: feeds back normally
Grid absent: interacts with Sunny Islands
Grid absent, genset on: Sunny Boy cut off from the system

I'd assume that they wouldn't lose much, if any production from the PV, 
since they'd probably be running the genset for short runs, at night, or 
in cloudy weather.

Best,

Hilton


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



-- 
Hilton Dier III
Renewable Energy Design
Partner, Solar Gain LLC

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