How do I commission a VAV airflow sensor?

VAV airflow sensors (typically pitot-tube arrays or velocity pressure sensors mounted at the box inlet) must be calibrated using a k-factor specific to the box size and inlet configuration. The calibration process involves measuring actual airflow using a calibrated flow hood (e.g., Shortridge or Alnor) at multiple damper positions and adjusting the controller's flow calculation until readings match within ±5% across the full range. The flow pickup should be verified to be centered in the inlet collar and the pressure tubing checked for leaks, kinks, or water traps that can cause significant errors. Per ASHRAE Guideline 36, the controller's flow measurement should be verified at the minimum cooling airflow, maximum cooling airflow, and at least two intermediate points — and the entire process should be documented in the commissioning report with as-found and as-left values. Modern DDC VAV controllers from JCI (FX-PCV series) and Siemens (ATEC series) have built-in auto-zero and auto-calibration routines that can simplify this process.