Removal and Replacement Procedures - Safety Considerations - PLAN AHEAD! 
188   HC900 Process Controller Installation and User Guide  Revision 19 
    06/14 
Replacing the Scanner Module 
Removing and replacing the Scanner Module from an I/O expansion rack (C50, C70, C75 CPU controllers 
only) requires that the source of AC power is removed from the rack.  Removing power from the 
Expansion rack has the following consequences: 
•  All power to all I/O modules in the rack will be lost; hence all control outputs from the rack to the 
process are lost. 
•  Redundant controllers will operate with the affected I/O in failsafe state during Scanner2 module 
replacement 
•  Does not impact other I/O Racks in the same configuration 
Table 36 – Scanner Module Replacement 
Step  Action 
1.  If a process is currently in operation, then: 
•  Either ensure that powering-down the expansion rack will not have adverse consequences on 
any running process, or 
•  bring the process to a safe and orderly shutdown. 
2.  Using an external (user-supplied) switch, disconnect the power supply or supplies in the 
expansion rack from the site AC power source. 
3.  Unplug the cable(s) from the scanner port(s). 
4.   At the top and bottom of the Scanner Module, loosen the captured screws that secure the module 
in the rack, and remove the module from the rack.  
5.  Configure the scanner address jumpers/DIP switches on the replacement module to match those 
of the removed module. 
6.  Ensure that the new Scanner Module is properly aligned with the slot guides, insert the new 
Scanner Module in the rack, and secure it in place with the captured screws at top and bottom of 
the module. 
7.  Re-install the cable(s). 
8.  Using the external (user-supplied) switch, connect the power supply or supplies in the expansion 
rack to the site AC power source.  The Scanner Module should resume communications with I/O 
modules in the rack and with the Controller Module with which it is connected. 
9.  Check status indications at the Scanner Module, at the Controller Module, and at the OI.