A key design requirement in most communications systems is
redundancy. It is expected that the system can survive “single fault”
conditions. The cooling systems for these products are designed
with N+1 redundancy for cooling. If any one airmover fails for
whatever reason, the cooling system needs to compensate for
the fault condition and maintain acceptable temperatures until
the problem unit can be replaced.
The redundancy requirement can be challenging, especially when
considering the full range of possible environmental conditions.
Airflow needs to be distributed evenly enough through the system
so that no card slots are “starved” for air during a failed fan condition.
A failed airmover not only stops contributing to moving the air but
can re-circulate or short circuit the air within the system and
further decrease the thermal performance.
