6.22 Fail class
All activated alarms must be configured with a fail class. The fail classes define the category of the alarms and the subsequent
alarm action.
The tables below show the action of each fail class for a genset controller when the engine is running or stopped.
INFO
All fail classes trigger the alarm Warning, which is shown in the active alarm log.
More information
See Option G5 Power management for mains and BTB controller fail classes. See Option G7 Extended power
management for plant and group controller fail classes.
6.22.1 Engine running
Fail class
Action
Alarm horn
relay
Alarm display De-load
Trip of gen.
breaker
Trip of mains
breaker
Cooling-down
genset
Stop genset
1 Block X X
2 Warning X X
3 Trip GB X X X
4 Trip + stop X X X X X
5 Shutdown X X X X
6 Trip MB X X X
7 Safety stop* X X X** X X X
8 Trip MB/GB X X X** X
9 Controlled stop* X X X X X X
*Note: Safety stop and Controlled stop are shown as identical, but they act differently: Safety stop de-loads and stops the genset if
other power sources are able to take the load; if not, the genset does not stop. Controlled stop de-loads the genset, but if no other
power sources are available to take the load, the genset trips the breaker and stops. This means that Controlled stop prioritises
protection of the genset, whereas Safety stop prioritises the load.
**Note: Safety stop only de-loads the genset before opening the breaker if option G5 (power management) is used. If power
management is not active, Safety stop is similar to Controlled stop.
***Note: Trip MB/GB only trips the generator breaker if there is no mains breaker present.
The table shows the action of the fail classes. If, for example, an alarm has been configured with the Shutdown fail class, the
following actions occur.
• The alarm horn relay activates
• The alarm is displayed in the alarm info screen
• The generator breaker opens instantly
• The genset is stopped instantly
• The genset cannot be started from the controller (see next table)
DESIGNER'S HANDBOOK 4189341275A EN Page 143 of 196
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