Description
In the Hardware Installation Manual, SINAMICS G120 Power Module PM240, Edition 07/2009 (entry ID: 52593268), the use of a line contactor for converters, frame size GX (160kW -250kW) is described. According to this description, the line contactor closes before the motor is switched-on – and opens after the motor has been switched-off (ON/OFF 1).
With Control Units (CUs) and firmware (FW) V4.0 up to V4.4, this switch-off procedure does not function as described. Although the contactor can be closed using an ON command, it cannot be opened using an OFF1 command.
From FW V4.5, this behavior has been resolved, and the line contactor can be controlled from the converter as described.

Solution for
CU230P FW V4.2, V4.3, V4.3.2, V4.4
CU240E FW V4.3, V4.3.2, V4.4
CU240B FW V4.3, V4.3.2, V4.4

For CUs with FW V4.x, a line contactor control, as described in the SINAMICS S120 Function Manual Drive Functions (entry ID:49084671), can be implemented.
Or the CU can be replaced by one with FW V4.5.

Solution for
CU240S FW V3.0, V3.1, V3.2

Although this function was not intended for CUs with FW V3.x, however, the application "MICROMASTER, SINAMICS G120: main contactor control using free function blocks (FFB)" (entry ID:22078212) can be used. Replacing a CU with FW V3.x by a CU with FW V4.5 is not possible as result of various hardware and software changes. 

Note
In the description of terminal block -X9, the load capability of terminals 5 / 6 is specified to be 230 V AC ± 15 %, 400 mA; this data is incorrect. The following data is correct: 240 V AC, 10 A.