CI820 Online replacement
Voted best answer
S800 IO MODULES are nicely available with Hot Swappable property(almost).
As your configuration is Redundant, thus YES you can go for online replacement.
Also your Redundant module has taken over clearly.
You have to take care for New Module's:
Same Software version,and the Cluster correct address.
(dont forget to take a healthy backup prior to this work)
For This Type of Works yes we can do it online
1- take the connection power for this CI820 out
2- you need xxxx driver and long to remove it
3- take care to remove it
4- give the same Address from the front
5- fix the new one
6- reconnect the power
7- wait for initialization