ABB S800 I/O - Page 110

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All I/O modules, except for relay output modules with normally closed contacts, can
be exchanged on-line and with the process power supply connected. This is possible
because the module deactivates when the I/O module lock switch is turned to
unlock.
It is important to understand the consequences of a module exchange on-line and
how it affects the process. Replacement of an S800 I/O module affects all channels
on the module. It also sometimes indirectly affects the outputs via some application
function, on another module.
The system software in the FCI checks automatically that all I/O modules function
correctly. In the event of module fault, and module exchange, the module and
associated signals are marked as faulty.
The system software checks that the module is inserted and correct. If this is the
case, the Fault-indicator (LED) extinguishes (after 10 seconds).
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In single or parallel operation of power supplies, there will always be a disturbance
of the function when a power supply must be replaced; the station will not have
power.
In a redundant power supply configuration, it is possible to replace a power supply
module without disturbance of the function. To achieve that the installation see
Section 3.1.2, SD811 and SD812 Power Supply Configurations and the correct
replacement procedure that follows.