User Guide

DEFINITY Enterprise Communications Server Release 5
Maintenance and Test for R5vs/si
555-230-123
Issue 1
April 1997
Maintenance Object Repair Procedures
Page 10-227CABINET (Cabinet Sensors)
10
alarm state. If there is at least a 15
0
C (27
0
F) air temperature difference between
the air exhaust and air intake, and if the air exhaust temperature is greater than
50
0
C (122
0
F), all the fans are turned up to high speed. If this condition exists,
the AHD1 circuit pack reports an air flow problem which results in a Minor alarm
against the Cabinet Sensors.
Variable Speed Fan Option. A variable speed fan is indicated by the Product
Code "ED67077 G‘x,"’ where ‘x’ is ‘4’ or a number greater than ‘4.’ A variable
speed fan contains Thermal Speed Control and an alarm circuit. As a result, the
AHD1 circuit pack is not required in this type of fan.
A variable speed fan has two connectors: a two pin connector for the -48 volt
input power for backward compatibility, and the five pin Molex connector for
speed control and alarm circuitry. The -48 volt power circuitry is isolated from the
speed control and the alarm circuitry.
An alarm lead from all six variable speed fans is tied to a single lead leading to
the processor circuit pack. Three fans on the front of the system are connected to
an S3 sensor, which monitors the exhaust air temperature above carrier position
"C." Three fans on the back of the system are connected to another S3 sensor,
which monitors the exhaust air in the power distribution unit. The speed of the
variable speed fans is determined by the temperature detected by the S3
sensors. Thus, the fans’ speed changes continuously according to the
temperature of the exhaust air. If the fan speed drops below the preset limit, or if
the fan fails, the fan alarm circuit reports an air flow problem, which results in a
minor alarm.
A multicarrier cabinet containing variable speed fans is presented in Figure
10-11. Note that the two S4 sensors that are included with non-variable speed
fans are not required with variable speed fans.
NOTE:
The new variable speed fans are backward compatible to the carriers for
the non-variable speed fans. However, the carriers for the variable speed
fans are not backward compatible to cabinets configured for the carriers
for the non-variable speed fans. Finally, the carriers for the non-variable
speed fans are not forward compatible to cabinets configured for the
carriers for variable speed fans.