SMA SI 4548-US - Manual (Page 138)

14 Connecting External Sources SMA America, LLC
138 SI4548-6048-US-BE-en-20 Operating Manual
In order to switch the signal circuit via the DigIn input, a single pole break contact or a single pole
auxiliary relay with a 120 V coil is necessary. If there is no auxiliary relay present in the ATS, you must
install an external contactor with a 120 V or 240 V coil. The coil is supplied with voltage via the utility
grid.
Treat this electric circuit as a communication circuit and do not connect it in parallel to AC voltage and
current cables. Running this circuit parallel to AC voltage and current conductors may cause
interference in the signal and give the Sunny Island an incorrect signal. No voltage should be present
on the relay during a grid failure. For external relays, pull voltage from the grid side of the transfer
switch.
The auxiliary relay can be a part of the automatic transfer switch or a separate assembly.
The signal circuit occupies two auxiliary contactors at the DigIn input:
1. Connect the negative terminal of the DigIn terminal to the negative terminal of the BatVtgOut
terminal.
2. Connect the positive terminal of the DigIn terminal to a NO terminal of an auxiliary contact of
the transfer switch.
3. Connect the positive terminal of the BatVtgOut terminal to the second contact of the same
auxiliary contact on the transfer switch.
An auxiliary contact is used because the Sunny Island must "know" whether it is connected to the utility
grid or whether it must manage a diesel generator.
To enable such an operation, you must set parameter "231.06 ExtSrc" to "GenGrid" (see Section 8.2
"Starting the Quick Configuration Guide (QCG)", page 68).
Settings performed on the generator and utility grid
All the settings made for the generator and utility grid in the sub-menus also apply to the
"GenGrid" selection.