10
Electrical connection
The storage system has two primary AC
terminals: one for the utility grid and one for the
micro-grid. These AC connections must be made
for the storage system to operate.
The Grid terminal inside the storage system
must be connected to grid service, usually at the
main utility panel. A main disconnect between
the storage system and the utility grid of equal or
greater rating than the supply feeder connection,
up to 200 amps, is recommended.
The storage system can pass through up to
200A from the grid to the protected loads panel
when the grid is available.
If you will be using a protected loads panel,
design the panel for a nominal current of 33A.
Although the unit has a 200A pass-through rating,
the system has a 33A continuous output when the
grid is down.
Special care must be taken to ensure the
main panel and the protected loads panel are
electrically isolated from each other when the
storage system is in backup mode. L1, and L2, and
N must have no connection between the two
panels outside of the storage system internal AC
terminals.
If you are not using a protected loads panel,
you can use the storage system’s built-in, 200-
amp automatic transfer switch to provide backup
power for your whole house.
Special care must be taken
with this type of configuration
since all loads in the house will be
powered when the grid goes down.
Typically, this results in severely
reduced backup times and poor
customer experiences.
In either case, the AC panel with the loads that
will be powered by the storage system (protected
loads panel) is connected to the micro-grid
terminals inside the storage system. The storage
system’s built-in transfer switches will disconnect
the utility when a loss of utility power is detected.
The micro-grid will now be powered by energy
produced by the PV array and the energy stored in
the storage system battery modules.
Off grid applications
The sonnen storage system can also be used
in off grid applications where no utility power is
available. This is an extreme application for the
storage system since it operates best when it is
connected to the grid and has a source of AC
coupled solar. However, there are many examples
of successful off grid systems using the sonnen
offerings, but those systems were designed with
assistance from the sonnen Design team. It is
highly recommended that any off grid system
receives this assistance before purchasing the
product. Failure to do so could result in a loss of
warranty conditions.
It is necessary to fully charge
the storage system (100% SOC)
in an off grid application at least
once a month. This could be a
challenge in an off-grid application
using only PV since the system has
been designed to turn off the PV
inverter at 95% (while in backup
mode) to avoid overcharging.
Therefore, it is mandatory that
a compatible generator be
installed on site to achieve the full
charge request. Failure to meet
this expectation could result in
warranty liability.