What is volumetric tracking in HVAC systems?

• A. A method to adjust air density in ducts.
• B. A method to monitor humidity levels in the space.
• C. A method to track outdoor weather patterns.
• D. A method to maintain a fixed difference between supply and return flow rates.

Answer: (D)

Volumetric tracking is a control approach that keeps a constant relationship between the air volumes moving through the system. Specifically, it maintains a fixed difference (delta) between the supply air flow to the space and the return air flow back to the air handler. By holding that delta steady, the system guarantees a predictable amount of outdoor/ventilation air is being introduced, even as room loads, leakage, or sensor readings change. The controller uses measurements of supply and return flow and adjusts fans or dampers to keep that delta constant, which helps meet ventilation requirements and manage energy use.

This concept isn’t about changing air density, monitoring humidity, or tracking outdoor weather patterns, which are separate control or monitoring tasks.