[RE-wrenches] Outback AC coupling Sunpower?

[Corey Shalanski]

Mac,

We have installed about ten AC coupled Magnum systems over the past year.

Overcharge protection is accomplished by frequency shift, but Magnum
recommends an auxiliary form of battery management. The cheapest way to do
this is to program the relay driver on the Magnum advanced remote control
(ARC) to open/close a solid state relay at specified battery voltage
setpoints - similar to what Kelly mentioned. Unfortunately the "cheapest
way" sometimes comes back to haunt us in the form of unanticipated extra
costs. We had two customer callbacks indicating their inverter had
mysteriously shut down - site visit revealed a fried relay in each case..
so I would recommend at least investing in a good quality relay if you
choose this route.

One other thing we have learned is that not all grid interactive inverters
are compatible with the Magnum inverters. Specifically Power One Aurora
string inverters cannot seem to synchronize in off-grid mode - we have had
to switch out Auroras on two projects because of this. We have had no such
synchronization issues with SMA inverters so far.

--
Corey Shalanski
Joule Energy
New Orleans, LA



On Wed, Jul 31, 2013 Mac Lewis <maclewis1 at gmail.com> wrote:
>
>
> Here is a paper on AC coupling the magnum.
>
> http://www.wholesalesolar.com/pdf.folder/inverter%20pdf%20folder/MagnumACcoupling.pdf
>
> The key is to connect the AC input terminals on the Magnum to the main
> panel (or a panel closer to the utility feed) and then feed the utility
> interactive inverter to a subpanel that is connected to the AC output
> terminals on the Magnum.  Under normal operation, the Magnum passes the
> power through and the utility interactive inverter is connected to the
> grid.  If the grid goes down, the internal relays isolate the Magnum and
> the critical load panel from the grid and the Magnum starts to make a sine
> wave that the UI inverter will export power to.
>
> You have to keep the critical load panel amperage below the pass through
> rating on the internal relays on the Magnum, and the grid connected
> inverter needs to have a lower output than the Magnum (I think by 10%).
>  Also, I'm not sure if the diversion controller Magnum has been working on
> is out yet or not.
>
> I've never done this, but I am about to.  Any wrenches have experience
> doing an AC coupled magnum?
>
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