Connecting External Sources
SMA America, LLC
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SI5048U-TUS121440
Technical Description
14.3 Generator and Grid
In addition to the public grid, a generator can also be integrated into an off-grid power system as a
secondary protective measure. This is particularly useful in case of long-term grid failures, even if the
battery size is no longer sufficient to bridge the failure after a period of time.
The standard solution in such cases is to use a transfer switch that can be purchased as a manual or
an automatic switch. By using such a switch, a diesel generator is connected to the AC2 connection,
to which the public grid is normally connected, as displayed in the figure below:
To use such a switch, proceed with the installation as follows:
1. Connect the negative pole of the DigIn connection on the Sunny Island to the negative pole of
the BatVtgOut connection, also located on the Sunny Island.
2. Connect the positive pole of the DigIn connection to a NO connection of an auxiliary contact
of the transfer switch.
NOTICE
Abrupt switching from the power distribution grid to the generator and vice versa.
Destruction of the Sunny Island.
• If an automatic switch is installed, make sure that the breaker completely disconnects
the Sunny Island from the grid and from the generator for at least 5 seconds.
• If a manual switch is installed, leave the switch in off-position for at least 5 seconds
before switching to the new position.
• Refer to the download area at www.SMA-America.com for further information on
how to install a switch for connecting the Sunny Island to the power distribution grid
and to a generator.
