Belimo controls reduce fan power in VAV systems
By enabling the fan in VAV air-distribution system to be controlled to deliver the required air volume rather than maintain a constant pressure in the duct, Belimo's MP-Bus system makes possible considerable improvements in energy efficiency. An installation in Switzerland monitored during the winter is said to have reduced fan energy consumption by 40%. The MP-Bus enables the damper position of the VAV controller in each zone to be monitored. The damper that is open the widest serves as a reference. The speed of the fan is reduced until this damper is about 85% open and other dampers are closed as required in response to lower airflow requirements. Since air volume is proportional to the speed of the fan and static pressure is proportional to the square of the fan speed, potential savings are immediately apparent. In addition, fan power consumption is proportional to the cube of the fan speed.