Doug,
In an ac coupled system with a Sunny Boy connected to the FX inverter's
output or to the critical loads panel, a grid connected Outback inverter
will work the same as it usually does - it is not affected by the Sunny
Boy other than by the rise of the ac feeder voltage. Just be careful to
not overload the FX's internal transfer switch - everything works
normally. As long as there is grid power and the Outback inverter's
internal transfer switch is closed, power (in excess of the critical
loads) from the Sunny Boy simply passes through the FX to the grid.
Problems arise when there isn't any grid power - that's when the system
is a micro grid - because all of the power must go someplace locally.
The FX inverter has no choice but to put all the energy from the Sunny
Boy into the batteries, so the FX becomes an unregulated battery
charger. When the batteries are (nearly) full, the Sunny boy must be
shut down. A voltage controlled switch or the FX inverter's Aux output
can open a relay to remove power from the Sunny Boy.
Kent Osterberg
Blue Mountain Solar
Doug Wells wrote:
Wrenches,
Howie, good to see you probing this issue.
I have an upcoming system as well that is considering a micro-grid
approach.
My question would be, is the Outback not able to sell back and charge
at the same time. I understand that with power present on the ac
output terminal the inverter will try to charge the battery. But
doesn't the unit also try to sell back on the AC output terminal.
Most Outback systems will sell down to the float voltage in a battery
back up situation that is grid connected. Does all of the DC
connected array stop selling back with the Sunny Boys going full steam.
For example. Lets imagine we have 4 kW connected to an Outback dual
inverter grid connected battery back up and then add 4 kW connected to
a Sunny Boy in a micro-grid format. When the sun is shining---and all
the loads in the critical panel are being met---that the Sunny Boy
overpowers the Outbacks and 1. Charges the batteries and 2.(my
question) overpowers the Outback's ability to sell to grid in its
traditional format?
As always the guidance of the "List" is greatly appreciated.
Thanks
Doug Wells
The Solar Specialists
www.thesolarspecialists.com
802-498-5856
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