Specific Fan Power (SFP) is normally required and controlled at maximum airflow rate. However, a DCV system will typically have airflow rates between 30 and 80% of the maximum airflow rate, depending on diverse factors for dimensioning and on the minimal ventilation rate. At maximum airflow rate, there are only small differences between the system’s SFP depending on the control strategy (Figure, r=1), but at lower airflow rates (Figure, r < 1), there are major differences depending on the control strategy. It is important to require a maximum SFP-value for two operating scenarios: maximum airflow rate and reduced airflow rate, in order to ensure an energy efficient control strategy.
The most important control points are presented in Figure.
The most important control points. Measurement of SFP with partial load, control of the compliance between airflow rate at room level and total airflow rate, and control that there is always one DCV damper in max open position with the help of the Building Management System (Schild&Mysen, 2009).
Source from article on “Commissioning for energy-optimal Demand-Controlled Ventilation” by Mads Mysen, Peter G Schild, Axel Cablé and John Woollett