MX240 Router Clearance Requirements for Airflow and Hardware Maintenance
When planning the installation site, allow sufficient clearance around the rack (see Figure 1):
For the cooling system to function properly, the airflow around the chassis must be unrestricted. Allow at least 8 in. (20.3 cm) of clearance between side-cooled routers. Allow 5.5 in. (14 cm) between the side of the chassis and any non-heat-producing surface such as a wall.
For service personnel to remove and install hardware components, there must be adequate space at the front and back of the router. At least 24 in. (61 cm) is required both in front of and behind the router. NEBS GR-63 recommends that you allow at least 30 in. (72.6 cm) in front of the rack and 24 in. (61.0 cm) behind the rack.
Airflow must always be from front to back with respect to the rack. If the device has side to rear airflow, then provisions must be made to ensure that fresh air from the front of the rack is supplied to the inlets, and exhaust exits the rear of the rack. The device must not interfere with the cooling of other systems in the rack. Fillers must be used as appropriate in the rack to ensure there is no recirculation of heated exhaust air back to the front of the rack. Care must also be taken around cables to ensure that no leakage of air in situations where recirculation may result.