Why HVAC PID Loops Hunt or Oscillate
PID hunting occurs when a control loop continuously overshoots and corrects without settling. In HVAC systems, this is usually caused by tuning that does not respect system dynamics.
Common Causes
- Excessive proportional aggressiveness
- Integral action correcting too quickly
- Control loop faster than the physical process
- Misinterpreted PID parameters
Stabilizing a Hunting Loop
- Reduce proportional aggressiveness
- Slow down integral correction
- Allow the system time to respond
- Confirm loop direction and limits
Stability almost always improves when tuning is adjusted to match physical system lag rather than forcing rapid correction.