Figure 2 shows the change of working point and power comparison, where c1 and c2 are system resistance curves under normal and fault conditions (dirty filter or evaporator); [P.sub.[omega]1] and [P.sub.[omega]2] are the fan head curves of a forward-curved fan, under speed [omega]1 and [omega]2; [W.sub.[omega]1] and [W.sub.[omega]2] are the fan-power curves under speed [omega]1 and [omega]2.
For radial and forward-curved fans, the fan power increases when the airflow rate increases.
For example, a housed forward-curved fan
operating at peak efficiency is actually more efficient than the same size housed airfoil fan.
For the forward-curved fan
represented in Figure 3b, a 20% increase in pressure drop from point A to point B would decrease airflow approximately 7%, and fan power draw would actually increase approximately 7%.
"Another popular energy-saving Trane feature is eDrive direct-drive plenum fan technology, which is up to 20 percent more efficient than traditional forward-curved fans
," he adds.
Regarding fan static, the value used was generated by use of software tools from a well-known manufacturer of forward-curved fans
. Finally, the 1.1 kW is unit power including controls and actuators.