Rockwell Automation 1756-DH485 ControlLogix Data Highway 485 Module Installation Instructions - Manual (Page 10)

10 ControlLogix DH-485 Communications Module
Publication 1756-IN587A-EN-P - September 2005
Install or Remove the Module While Power Is Applied
You can install or remove the module while chassis power is applied if you
observe the following precautions.
Be sure that power is removed or the area is nonhazardous before proceeding.
Repeated electrical arcing causes excessive wear to contacts on both the
module and its mating connector. Worn contacts may create electrical
resistance that can affect module operation.
WARNING
When you insert or remove the module while backplane power
is on, an electrical arc can occur. This could cause an explosion
in hazardous location installations.