Free cooling is used during the summer to cool the building at night-time using cool outdoor air.

Installation of outdoor and room temperature sensors is required. Alternatively, intake air and extract air temperature sensors can be used.

In that case, the function performs temporary starts of the AHU (default: 3 min run every 60 min) for temperature sampling.

Operation will continue if measured temperatures fulfill the condition for running. Otherwise the operation will stop after 3 minutes and retry after 1 hour.

Free cooling is only activated when all conditions are fulfilled:

  • The unit is stopped by the schedule.
  • The unit is scheduled to run in next 72 hours.
  • Less than four days have passed since the unit was last in running mode.
  • The outdoor temperature during the previous running period exceeded a set limit [22] °C.
  • Current outdoor temperature is within permissible limits [10] > Outdoor temperature < [18].
  • Current room temperature is > [18] °C.
  • Current time is between 00:00 and 07:00.

When free cooling is active, the fans run at normal speed or the set value for pressure/flow control. An offset can also be entered for the fan setpoints during free cooling.

After free cooling has been active, the heating output is blocked for [60] minutes.

Settings and configuration of Free cooling


Available options & Selection


Activate Free cooling function

Configuration > Functions > Function activation

Free cooling

| Yes | No |


Activate temperature sensors

Configuration > Functions > Temperature control

Room temperature sensor

| No | 1 | 2 | 3 | 4 |

alternative: Extract air temperature sensor

Outdoor temperature sensor

| Intake air | Outdoor | Outdoor + Intake air |

alternative: Intake air temperature sensor

Configure inputs

Configuration > I/O allocation settings > Analog inputs >

Room temperature 1

Any available I/O


Outdoor temperature


Operational settings

Data & Settings > Demand control > Free cooling

Free cooling mode

Not active | Active

Indication of function status

Running when day outdoor temperature >

[22] oC

Settings for run condition check

Stop when night outdoor temperature >

[18] oC

Stop when night outdoor temperature <

[10] oC

Stop when room temperature <

[18] oC

Free cooling start hour


Free cooling is activate during period 0:00 - 7:00

Free cooling stop hour


Time to block heat output after free cooling

[60] min

Heating is blocked after free cooling for 60 min.

Fan-kick temperature check

[180] s

Only work if: Intake air is used instead of Outdoor air sensor and/or Extract air is used instead of Room temperature sensor. Fans start for 180 s every 60 min to allow sensors to measure the temperatures

Fan-kick interval time

[60] min

Configure fan offset

Data & Settings > Fan control > Fan setpoints

Offset supply air fan when free cooling

[0] Pa


Offset extract air fan when free cooling

[0] Pa


Chapter info                              

Last reviewed: 11/29/2021

Access version: 4.6-0-14 (3045)