The objective of this research project was to obtain a body of measured inlet and discharge system effects for both air and sound for two typical sizes (15", 27") airfoil centrifugal plenum fans. The inlet appurtenances tested in this project were as follows: a typical pillow block bearing, an inlet cabinet with different side wall spacings, an inlet cabinet with a coil at four axial spacings from the fan inlet, and a return fan inlet cabinet with four different side wall spacings and with a 45-degree baffle. The outlet appurtenances were outlet cabinets with different side wall spacings. The fan was tested at one speed for all the inlet or outlet configurations. The tests were performed at the Air Movement and Control Association (AMCA) International laboratory in Chicago.

As can be expected, the measured system effect varied according to the amount of flow disturbance created by the appurtenance. For example, there were some side wall configurations that rendered the fan completely unstable, which made the calculation of system effect meaningless. On the other hand, there were bearing configurations that had a negligible system effect.

This project benefits the public by providing information to the system designer that aids in their understanding of the effects that the system has on the fan employed in it.