TB9100/P25 CG/P25 TAG Installation and Operation Manual Description 29
© Tait Limited March 2014
Front Panel Fans
The front panel can be equipped with up to two fans. One fan is for the
PMU and the other is for the PAs. (Reciters also have fans, see “Reciter Fan
Operation” on page 121.)
Front panel fans do not operate continuously but are switched on and off as
needed by the reciter firmware.
When the base station powers up, the fans turn on: the PMU fan runs first,
followed by the PA fan (the reciter fans will also power up, after the PA fan).
Each fan will run for about 5 seconds before switching off.
Front panel fans must have the correct wiring: power and ground (2-wire
fans), or power, ground, and rotation detect (3-wire fans). Both fans in a
subrack must be of the same type. If 3-wire fans are fitted, the reciter can
monitor whether the fans are rotating and generate an alarm if the fan fails.
The control and monitoring of the fans is performed by the reciter selected
at the control panel. We recommend that you enable the fan alarms for
reciter 1 and disable the fan alarms for the other reciters.
Configuring Fan
Control
The operation of the PA fan is configurable via the CSS; you can specify the
threshold temperature at which the fan will be turned on, and set the fan to
operate only when the PA is transmitting.
The PMU fan has fixed on/off thresholds and a defined set of duty cycles
based on the PMU temperature and load current, as described in the
following table.
PMU Temperature Current Fan Duty Cycle
<149°F (65°C) <4A
4A–6A
6A–8A
8A–12A
12A–14A
≥15A
always off
2 minutes on, 8 minutes off
2 minutes on, 5 minutes off
3 minutes on, 3 minutes off
4 minutes on, 1 minute off
always on
>149°F (65°C) –– always on
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