HP Netserver L Server series - Manual (Page 50)

Chapter 7 Installing Additional Power Supplies
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Ventilating Fans
HP NetServer fans are placed to ventilate and cool internal components. The LH
4 and LH 4r use a redundant fan assembly with two fans that mount directly in
front of the fans cooling the power supplies. In general, if any one fan fails, the
NetServer will continue to operate, but if two fans fail, thermal shutdown will
occur.
CAUTION The NetServer must have its covers in place for proper
cooling. If you open the NetServer while it is operating, do
not run it for more than three minutes.
Do not run the NetServer for more than two minutes without
at least one working fan in the fan assembly mounted
immediately behind the power supplies or in the exhaust fan
assembly. Failure to observe these precautions may result in
thermal damage to the NetServer.
Servicers can hot-swap any fan except the processor fan. If
this fan fails, or if the metal baffle is removed, thermal
damage to the NetServer can occur.