After power-up, all segments light up for about 3 seconds. The FAU unit starts in Normal mode (ON) to display the current room temperature, user navigation icons and status of the application according to factory settings. Then the unit is ready for commissioning by qualified HVAC staff.
The control parameters of the fresh air fan controller can be adjusted to ensure optimum performance of the entire system (see Control parameters).
External circulation (factory setting)
The unit is set with the factory setting for external circulation (
) only and 3-speed manual fan (P54 = 3), i.e. P02 = 1, P24 = 0, P25 = 0 and P26 = 1 (see Control parameters).
Alternatively, some fresh air units or purifiers are equipped with an ECM fan (P54 = 4). This allows user selection of low, medium and high fan speeds.
Depending on use cases, users can also select P54 = 1 (1-speed fan) or P54 = 2 (2-speed fan).
Bypass function
When P24 = 1, bypass heat recovery is enabled, i.e. users can select external circulation (without heat recovery) and with heat recovery 
.
Internal circulation
When P25 = 1, internal circulation is enabled, i.e. users can select both external and internal circulation 
.
When P24 = 1 and P25 = 1, users can select all modes (, , ) via setting button 
.
Selection of FAU ECO mode
Except ON/OFF mode selection, users can select different modes for air flow. When P02 = 2 and P25 = 1, users can select FAU ECO mode 
via On/Off button 
.
With FAU ECO mode is selected with the factory setting of P26 = 1 (1:5), the unit switches to external circulation for 10 minutes, then internal circulation for 50 minutes within one hour.
The mode setting repeats automatically within one hour. Other ratios can be selected via P26.
When FAU ECO mode is selected and P24 = 0, operation mode is external circulation without heat recovery function. Otherwise, when P24 = 1, operation mode is external circulation with heat recovery function.