Juniper EX4650 Series, Hardware Manual, Page: 37 / 195

Figure 15: Back-to-Front Airflow Through EX4650 Switch Chassis
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Ports FRUs
You must install only power supplies that have AIR IN (AFI) labels in switches in which the fan modules
have AIR IN (AFI) labels.
Do Not Mix AIR IN (AFI) and AIR OUT (AFO) Components in the Switch
Do not mix power supplies and fan modules with different airflow labels (AIR IN (AFI) and AIR OUT (AFO))
in the same chassis. If the fan modules have AIR IN (AFI) labels, the power supplies must also have AIR IN
(AFI) labels; if the fan modules have AIR OUT (AFO) labels, the power supplies must also have AIR OUT
(AFO) labels.
The labels on the power supplies and fan modules should match the labels on the switch chassis.
Mixing components with AIR IN (AFI) and AIR OUT (AFO) labels in the same chassis hampers the
performance of the cooling system of the switch and leads to overheating of the chassis.
CAUTION: The system raises an alarm if a fan module fails or if the ambient temperature
inside the chassis rises above the acceptable range. If the temperature inside the chassis
rises above the threshold temperature, the system shuts down automatically.
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