What is the purpose of a static pressure reset strategy in a VAV system?

The purpose of a static pressure reset strategy in a VAV (Variable Air Volume) system is to reduce energy consumption by minimizing the fan energy required to deliver conditioned air to the zones served by the system, while still maintaining adequate airflow to meet the cooling or heating demands. A VAV system controls the temperature in individual zones by varying the amount of conditioned air supplied to each zone through VAV boxes. Static pressure is the pressure in the ductwork, and it's maintained by adjusting the supply fan speed. In a traditional VAV system, the static pressure is typically maintained at a fixed setpoint. However, with a static pressure reset strategy, the static pressure setpoint is automatically adjusted based on the actual airflow demand of the zones. When fewer zones require maximum airflow, the static pressure setpoint is lowered, reducing the fan speed and saving energy. Conversely, when more zones require maximum airflow, the static pressure setpoint is increased to ensure adequate airflow to all zones. This dynamic adjustment of the static pressure setpoint optimizes fan performance and reduces energy waste without compromising occupant comfort. The reset is often based on the VAV box damper positions; if most dampers are relatively closed, the static pressure can be reduced.