Cooling Subsystem; Figure 11. Fan Array With Four System Fans Installed - IBM @server xSeries 343 Product Manual

Cooling Subsystem

All system components except the power supply cage are cooled by a set of fans mounted near the
middle of the chassis and behind the hard drive bays. This is shown in Figure 11.
J8A1 J8A2
J8A3 J9A1
Fan Array Assembly
TP00473

Figure 11. Fan Array with Four System Fans Installed

®
The IBM xSeries 343 server comes in a non-redundant, four-fan configuration that
consists of two 80mm x 38mm fans and two 40mm x 28mm fans.
Air flows in through the front bezel over the peripheral bay and the hard drive bays, passes through
the fans and over the baseboard, and exhausts through the rear of the chassis. Each fan provides
tachometer signal output to the server baseboard to indicate a fan failure.
The cooling subsystem contains a fan array (as shown in Figure 11) consisting of two 80 x 38 mm
fans and two 40 x 28 mm fans to cool the server board and other components. A fan failure is
indicated by one of the fault LEDs located on the front panel.
Ambient Temperature Control
The server baseboard contains a pulse-width-modulation (PWM) circuit, which cycles the 12 VDC
fan voltage to provide quiet operation when system ambient temperature is low and no fan failures
exist. There are 16 fan speed settings between 20 °C and 35 °C, with the lowest fan speed setting at
20 °C or below. When the room ambient temperature exceeds 35 °C, the fan control circuit ceases
cycling and delivers 12 VDC. Following a room temperature excursion above 35°C the fan voltage
does not reenter PWM mode until the room temperature drops below 35 °C and all fans are
operational.
30 System Description