7.3.4 Set Up Alarmable Inputs in Latched or Unlatched Mode
Alarmable input points may be set up in Latched mode (Y), which requires
the user to clear the Liebert AC4 alarms after an alarm has occurred, or
Unlatched mode (N), in which alarms will automatically clear after a return-
to-normal state. The default setting for alarmable inputs is Y(Latched).
Any input defined as an event is automatically Unlatched.
An input defined as Latched does not reset automatically after an alarm. It
will remain in the triggered position even after the monitored device
returns to normal. After an alarm, the user must manually reset Latched
inputs, as described in Clear Active Alarms on page66. This also means
that any outputs linked to a Latched digital input will remain triggered
until the input is manually reset.
An input defined as Unlatched will automatically track the status of the
monitored device. No action by the user is required.
• From the Setup Inputs Menu, choose Latched, as shown above
right, and press Enter.
• To change this feature, use the arrows to choose Y (Yes -
Latched) or N (No - Unlatched), then press Enter.
NOTE: Only alarmable input points may be set up as Latched. If you
attempt to set up an event as Latched, the message shown at right
appears. Press the ESC key to return to the previous screen to continue
configuring the digital input.
The only way to reset latched alarms is by clearing active alarms. This step
is required to return latched points to their normal state. For details, see
Clear Active Alarms on page66.
7.3.5 Set Up Delay Time
Each input may be set up with a specified time delay between the
occurrence of an alarm or event—a monitored device changes state—and
any response by the Liebert AC4. This feature can prevent needless
responses to transient conditions.
This delay is the amount of time that must elapse before the Liebert AC4
acknowledges the change of state in the monitored device and takes any
further action, such as dialing configured pagers. The default time delay is 1
second (displayed as 00 MIN : 01 SEC).
The time delay applies only when a monitored device changes from its
normal state—for example, the Liebert AC4 detects a closed contact that is
defined as Normally Open.
When the monitored device returns to its normal state, the Liebert AC4
acknowledges the change of state after the delay timer ends its countdown.
• From the Setup Inputs Menu, choose Delay, as shown at right, and press Enter.
• To change the time delay in minutes and seconds (in the range of 00:00 to 99:59):
Vertiv | Liebert® AC4 User Manual | 47
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