### Multiple Fans

**FANS IN PARALLEL**

A parallel arrangement of fans is characterized by the same pressure increase across each fan and the total flow is the sum of flows through each individual fan. In the figure below, the total flow is shown as x1 + x2 + x3, where xn is the flow through fan “n”. The resulting total pressure is equal to each individual fan pressure, since they are all the same

**FANS IN SERIES**

Fans in series are characterized by the same flow across each fan and the total pressure increase is the sum of the pressure increase through each individual fan. In the figure on the following page, the total flow is shown simply as y, which is consistent throughout each fan. The resulting total pressure is equal to sum of each fan’s individual pressure increase, y1 + y2 + y3, where yn is the resulting fan pressure increase at fan “n”.