WhisperGreen Select's Multi-Speed with Time Delay* allows you to select the proper CFM settings to satisfy ASHRAE 62.2 continuous ventilation requirements. The fan runs continuously at a preset lower level (0, 30-100 or 0, 50-120 CFM, in 10 CFM increments), then elevates to a maximum level of operation (50-80-110 or 110-130-150 CFM) when the wall switch is turned on, or when the Motion Sensor or Condensation Sensor module is activated. A High/Low delay timer returns the fan to the preset CFM level after a period of time set by the user. *Applies to both the Pre-Installed Multi-Speed with Time Delay, as well as the FV-VS15VK1 Multi-Speed with Time Delay Plug 'N Play module.