Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
The Fan:VariableVolume module uses a polynomial relationship to set fan power as a function of flow rate only. Because it's only a function of flow rate, the fan is not controlled to a static pressure setpoint as it would typically in a real building. The flow rate is controlled by the terminal controllers, and this flow rate is sent to the fan to calculate the power usage based on the polynomial relationship. I believe the default in Open Studio corresponds to a VFD driven fan with a fairly aggressive static pressure reset. You could also modify the coefficients to model inlet vane or discharge damper control.
The Fan:ConstantVolume module doesn't have this relationship, so it consumes the same power regardless of the system flow rate.
