Juniper QFX5240 - Page 43

Figure 21: AFO Airow Through the QFX5240 Chassis
Power Supply Cooling System
The QFX5420 power supply modules (PSMs) are installed at the rear of the chassis. The PSMs are self-
cooling. Each PSM has its own fan and is cooled by its own internal cooling system.
NOTE: The PSU fan speed is regulated by the internal microcontroller rmware of the PSU. This
speed varies from 4000 RPM to 28,000 RPM depending upon the load condions and
temperature variaon.
WARNING: The PSU fan speed variaons are in range of 18,000 RPM to 28,000 RPM
based on the PSU internal higher temperature condion, This does not aect the
system funconality or the lifespan of PSU fans.
The PSMs in an QFX5420 switch support front-to-back airow (airow out or AFO).
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