As a result, the maximum relative airflow must be constrained to 1.

Equation 22 can be used to determine the required fan settings for a given total relative airflow.

The conversion process between a relative airflow setpoint and the discrete fan control involves choosing the set of discrete fan settings from the table that produces a tower airflow closest to the desired flow, assuming that airflow is proportional to fan speed.

According to Equation 22, the fan-speed setting if all cells are operating is equal to the relative airflow setpoint.

Then, for each entry in the table, the required fan control settings for the variable-speed fans that give the required relative airflow are determined using Equation 22, assuming that all the variable- speed fans operate at the same speed (see step 2).