Temperature sensors are used as part of the control package to alarm or shut down the AHU in order to prevent coil damage. Sensors are also used to prevent air below a low temperature limit setpoint from being discharged into the occupied spaces. The choice to only alarm or to shut the unit down is relative to the type of space the unit serves. Hence, shutting the unit down may be a major problem in facilities such as hospitals, laboratories, or process environments.
The typical air handler has these basic components: outdoor air intake, return air connection, control dampers, mixing area, filter bank, heating coil (pre heat or basic heat), cooling coil, reheat coil, fan, and the appropriate control sensors. Low-temperature conditions must be considered for each of these components in order to prevent operational problems that would affect the occupied space conditions.