M40E Cooling System Description; Cooling System Components; Airflow Through The Chassis - Juniper M40E Hardware Manual

M40e Multiservice Edge Router Hardware Guide

M40e Cooling System Description

Cooling System Components

Airflow Through the Chassis

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The cooling system includes a fan tray and several impellers that draw room air into the
chassis to keep its internal temperature below a maximum acceptable level. When the
temperature is below the maximum, the fans and impellers function at less than full
speed. If the MCS detects that the temperature of a component has exceeded the
acceptable maximum—for example, because an impeller is removed—it automatically
increases the speed of the remaining impellers and fans to reduce the temperature. The
fans and impellers can function at the higher speed indefinitely.
Cooling System Components on page 48
Airflow Through the Chassis on page 48
The cooling system has the following components. All are hot-removable and
hot-insertable, as described in "M40e Field-Replaceable Units (FRUs)" on page 157.
Air intake vent, air filter, and intake cover—Provide an opening for room air to enter the
router. They are located at the bottom of the chassis front, below the cable
management system, as shown in "M40e Chassis Description" on page 8. The air filter
is removable and covers the air intake vent, preventing dust and other particles from
entering the cooling system. For maintenance and replacement instructions, see
"Maintaining the M40e Air Filter" on page 130. The nonremovable air intake cover is
located behind the air filter and provides EMC shielding.
CAUTION: Do not remove the air filter for more than a few minutes while
the router is operating. The fans and impellers are powerful enough to draw
in foreign material, such as bits of wire, through the unfiltered air intake,
which could damage router components.
Front cooling subsystem—Cools the FPCs, PICs, and midplane. It includes a fan tray
located behind the cable management system and a large, central impeller behind
the craft interface. For replacement instructions, see "Replacing the Fan Tray on an
M40e Router" on page 168 and "Replacing the M40e Front Impeller Assembly" on
page 172.
Rear cooling subsystem—Cools the SFMs, host module, PCGs, and power supplies. It
includes one impeller located at the upper right of the chassis rear and another at the
lower left, as shown in "M40e Chassis Description" on page 8. The upper and lower
impellers are not interchangeable. For replacement instructions, see "Replacing the
M40e Rear Lower Impeller Assembly" on page 175 and "Replacing the M40e Rear Upper
Impeller Assembly" on page 177.
Figure 32 on page 49 shows airflow through the chassis and the location of the impellers
and fan tray.
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