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Battery Backup Unit (BBU) — Installation & Maintenance Manual Continued
4.5 Fail Position - The actuator position during a power loss is determined by the close/Open switch
setting [Figure 12] on the BBU. The switch setting is only recognized at the time of a power failure.
Alarm Relay Contact - The BBU provides a voltage free relay contact shown in Figure 12 which is
normally open. The contacts close when the batteries cannot hold a charge and require
replacement. When power is applied to the BBU for the first time or when power is reapplied after a
power failure, the BBU commences a battery charge cycle. Depending upon the depth of
discharge and the condition of the batteries, a charge cycle can range from under 1 hour up to 8 hours.
When a charge cycle operates for more than 12 hours, this indicates that the batteries can no longer
hold a full charge and must be replaced resulting in the Alarm Relay Contact closing.
N.O
OPEN
N.C
CLOSE
FAIL POSITION
ALARM
Figure 12
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