Air handler applications are designed with an Application Mode input which allows the user to force the unit into a mode of operation. The possible modes are Cool Only, Heat Only, Fan Only, Water Flush, Purge, Vent, and Auto. Some air handler applications may need to support all of these modes, and other applications may only need a few. This module is designed to override the modes not required by the application. This module has inputs for the Application Mode and for each mode in the application mode enumeration set. The module has an output for the effective mode. As an example, an application may not support purge mode so the user could change the purge mode to vent. Therefore, purge mode is overridden to vent. This module is implemented as a control activity.