HP Carrier-grade cc3300 UserÆs Guide and Technical UserÆs Gu - Page 35

HP cc3300 Carrier Grade Server Product Guide Cc3300 Internal Disk Drive Product Numbers Product Number Disk Capacity Rotational speed Disk Replacement Part Number A6917A 18 GB 10,000 RPM A6917-69001 A6942A 18 GB 15,000 RPM A6942-69001 A6918A 36GB 10,000 RPM A6918-69001 A6943A 36 GB 15,000 RPM A6943-69001 Cooling Subsystem The cooling subsystem contains a fan array consisting of two 80 x 38 mm fans and two 40 x 28 mm fans to cool the server board and other components as shown in Figure 9. A fan failure is indicated by one of the fault LEDs located on the front panel. OM12820 Figure 9. Fan Array with Four System Fans Installed Air flows through the bezel, over the peripheral bay and the hard drive tray, passes through the fans, over the server board, and exhausts through the rear of the chassis. Each fan provides a tachometer signal output to the server board to indicate a fan failure. Ambient Temperature Control The server board contains a pulse-width-modulation (PWM) circuit, that cycles the 12 VDC fan voltage to provide quiet operation when system baseboard temperature is low, and there are no fan failures. Under normal baseboard temperature conditions (less than 45 °C), the fan power circuit supplies an effective fan voltage of 7.0 VDC. When the baseboard temperature exceeds 45 °C, the fan control circuit ceases cycling and delivers 12 VDC. Following a baseboard temperature excursion above 45 °C the fan voltage does not reenter PWM mode until the baseboard temperature drops below 45 °C and all fans are operational. The cooling subsystem' design meets acoustic and thermal requirements at the lower fan speed settings. At the higher fan speed settings, thermal requirements are met for the maximum ambient temperatures but acoustic requirements may be exceeded. Chassis Description 35