What does the term "short cycling" mean?

Question

Options

• AThe fire suppression system clean agents are running low and have not been recycled.
• BCool air from the CRAC bypasses the IT equipment and flows directly into the CRAC return air duct.
• CThe raised floor is obstructed with excess cables and cool air is not getting through the vented floor tiles.
• DThe UPS supplies less runtime than anticipated because of overall wear and tear on the internal batteries.

• A
  5% (1)
• B
  79% (15)
• C
  5% (1)
• D
  11% (2)

Explanation

Short cycling describes a cooling inefficiency where cold air from a CRAC (Computer Room Air Conditioning) unit skips past the IT equipment entirely and loops back directly into the CRAC's return air intake, creating a wasteful closed loop that leaves servers underserved. Option B is correct because this bypass behavior is precisely what the term names - the airflow completes a "short" circuit rather than traveling through the full intended path across the hot equipment. Option A is wrong because fire suppression agents and recycling have nothing to do with airflow dynamics. Option C describes a raised-floor obstruction problem, which is a different issue (inadequate airflow delivery) rather than a bypass. Option D describes battery degradation in a UPS, which is a power system problem entirely unrelated to cooling airflow.

Memory tip: Picture the word "short" literally - the air takes a shortcut, cycling back to the CRAC before it ever reaches the equipment it was meant to cool.

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