Schneider Electric 840 USE 106 0 manual Through, Register, p

Maintenance

Forcing a	You can force a switchover using the RDE or, if you have programmed a CHS
Switchover	instruction in ladder logic, a Zoom screen. The instructions are the same; however,
Through	in the RDE you are working with the command and status registers, while in the
Software	Zoom screen you are working with the command and status pages.
	Step	Action
	1	Addressing the Primary controller: Check the status register or page to be sure
		one unit is designated A and the other is B. Be sure that both the Primary and
		the Standby controllers are in run mode and that the function keyswitch override
		has been enabled.
	2	In the command register or on the command page, take the Primary controller
		offline.
	3	If you are operating on a Modbus Plus network, the programming panel is
		automatically communicating with the Primary controller. If you are operating via
		the Modbus or Modbus Port directly connected to the original primary controller,
		you must reconnect the programming cable to the new Primary controller and
		then log in again, due to the port address swap.
		Result: The status should now show that the original Primary controller is offline
		and that the Standby is now functioning as the Primary unit. Refer to Command
		Register, p. 76.
	4	Check the LED displays on the Hot Standby modules to confirm that the
		switchover has taken place. The Primary indicator on the original Primary unit
		should be extinguished, while the Primary indicator on the original Standby unit
		should be a steady green.
	5	In the command register or on the command page, return the original Primary
		unit to RUN mode. The status register or page and the LED display on the front
		panel of the Hot Standby module should now show that unit in Standby mode.

204 840 USE 106 00 January 2003