Alarms
The red LED is normally dark. The LED is lit for A- and B- alarm conditions.
The LED is dark for alarm condition: the (absolute) supply voltage is below
15 V.
Table 41 Fan Unit Alarms
Fan alarm_A is active when one or
more of the conditions is/are:
-48V is too low (towards 0 V) or
the temperature is above 65
degrees C
Fan alarm_B is active when one or
more of the conditions is/are:
one -48V input is missing or
the temperature is above 55
degrees Cor
the tempsensor fails or
the FAN or motor regulation fails
The alarm_a signal is tied to ground when alarm A is active while the alarm_b
signal is open when alarm B is active
7.5 AC/DC Unit Alarms
Connect the AC/DC unit alarm relay contacts to the inputs of the ALU2 board
through the MDF according to the cabling list for the site. The inputs of the
ALU2 are internally tied to -48 V through serial resistors and the board can
therefore detect loop or closing to 0 V. The resistance from the source to the
ALU2 input should be maximum 20 kohm.
7.5.1 115-230 V System
One power source is the Cherokee Power System, described earlier, see
Section 4.6.2 on page 48. It has a set of ports, alarm contacts, located on the
top left side, that reflect different operating conditions for the power supply,
see Figure 109 on page 134. Wires to the ALU2 alarm unit can be fastened
to the different ports.
133
6/1531-ASP 113 01 Uen J2 2008-07-17
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