10
2.5.3 Alarm Relay Contact States
All alarms contacts for the A75D(E) are designed to be fail-safe. In other words, if both the AC and DC power
are removed, each alarm will be indicating in its correct state. To accomplish this, certain alarm relays are de-
energized on failure (such as AC Failure), and certain alarm relays are energized on failure (such as High DCV).
All relay contacts are shown in the de-
energized state on schematics. Set A
alarms are shown in non-alarm state on
the schematic. Set B alarms are shown in
alarm state on the schematic. Customer
alarm connections should be made
accordingly.
2.5.4 Alarm Connection Procedure
Before
making any connections to the A75D(E) ensure that the AC Power is off at the main breaker box and that both of
the unit’s breakers
are off. Verify that no voltage is present by using a voltmeter at all input and output terminals.
For alarms in Set A (Energized on Alarm):
If it is desired that the annunciator be active until the alarm triggers
connect the annunciator leads to the
NC
and
C
contacts of the desired
alarm (located on the Relay Alarm Connect Card
S2A-198B
). If it is
desired that the annunciator be activated after the alarm triggers
connect the annunciator leads to the
NO
and
C
contacts of the desired
alarm.
For alarms in Set B (De-Energized on Alarm):
If it is desired that the annunciator be active until the alarm triggers
connect the annunciator leads to the
NO
and
C
contacts of the desired
alarm (located on the Relay Alarm Connect Card
S2A-198B
). If it is
desired that the annunciator be activated after the alarm triggers
connect the annunciator leads to the
NC
and
C
contacts of the desired
alarm.
Example connections
The example shown in Figure 7 demonstrates how a customer might connect the AC failure contacts. The AC
failure relay is de-energized on alarm, so the Speaker and the Red Lamp connected to the Normally Closed
contacts will activate under the AC failure condition. The Green Lamp connected to the Normally Open contacts
will be active when AC power is present, effectively acting as an external AC On Lamp.
Energized on Alarm (Set A)
De-Energized on Alarm (Set B)
High DCV
AC Failure & Summary (S2A-364 card)
High DCV Shutdown
Low DCV
Positive Ground
End of Discharge
Negative Ground
Low DCA
Charger
Failure
Table 8 - Relay Contact State on Alarm
Figure 9 - Example Connections
(Customer Provided Equipment)
