If axial fans or inline fans are being considered, select each fan for the flow rate required and one-half of the system total pressure requirements. If they are known only in terms of static pressure, total pressure values may be calculated by adding the velocity pressure corresponding to the velocity passing through the outlet of the second stage fan to the system static pressure requirements.Ģ. Establish the system requirements in terms of total pressure. What is the quickest and easiest way to select two fans in series?ġ. These losses must be added to the normal system resistance requirements. There may also be bypass ductwork around the second fan if only one fan is run for a period of time. Total pressures are used instead of static pressure because the fans can actually be different sizes and a change in fan or connecting duct areas has an influence upon static pressure values. The combined total pressure across both fans will be the sum of the individual total pressure of each fan. To simplify selection and control, two fans of the same size are typically used with the required flow rate defined by the inlet conditions of the first fan. RATING TWO FANS IN SERIES Two fans in series are normally rated as a single unit in order for AMCA rating definitions and practices to apply. (Click on the image for an enlarged view.)
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