Correct AnswerB. Vary the airflow to a zone based on its temperature needs
Quick Explanation
A VAV system primarily varies the quantity of supply air delivered to each zone according to its thermal demand while the central supply-air temperature is usually maintained within a controlled range. VAV boxes modulate airflow using dampers/controls.
Detailed Explanation
Concept & Reasoning
When zone cooling demand falls, the VAV terminal reduces airflow; when demand rises, it opens to supply more air. This reduces fan energy compared with constant-volume systems, especially when a variable-speed supply fan tracks duct static pressure. Some VAV terminals may include reheat for minimum-flow/temperature control.
How to Solve It in the Exam
VAV = Variable Air Volume → airflow changes.
Important Exam PointDo not confuse VAV with constant-air-volume systems that vary temperature more directly.
Related Revision Path
This question sits in the revision path Building Electrical Services → HVAC → Air Distribution .
