How to Tune VAV Box PID Loops

VAV box PID loops behave very differently from AHU-level loops. Terminal units respond quickly, have limited authority, and are easy to overtune.

Common VAV Tuning Problems

• Rapid damper hunting
• Short cycling of reheat valves
• Noise complaints
• Inconsistent space temperature

Why VAV Loops Are Sensitive

VAV boxes typically control small air volumes with fast feedback. Aggressive tuning that might work at the AHU level often causes instability at the terminal level.

Recommended Approach

• Use conservative proportional response
• Keep integral action slow or minimal
• Avoid derivative unless explicitly required
• Confirm valve or damper direction

In most cases, stable VAV performance comes from tuning that prioritizes smooth response over speed.