Pretreatment function enables utilization of the geothermal preheating and precooling of the intake air.

The function activates "Pretreatment start" output once the outdoor temperature passes the activation threshold. The digital output Pretreatment is activated when the unit is started and the outdoor temperature is below the set heating start limit (default 8 °C) or when the outdoor temperature is above the set cooling start limit (default 19 °C).

If the outdoor temperature exceeds the set preheating start limit by more than 1 °C, preheating will be stopped, as well as if the outdoor temperature falls below the precooling start limit by 1 °C.

The function can work with just the outdoor temperature sensor present. If the intake temperature sensor is added - the temperature difference of both sensors is used as additional start condition.

If the temperature in the intake duct does not exceed the outdoor temperature by more than 1 °C (adjustable) 5 minutes (adjustable) after start-up when using preheating, preheating will be stopped. The same conditions apply to precooling, i.e. if the intake temperature is not more than 1 °C (adjustable) cooler than the outdoor temperature, precooling will be stopped.

Pretreatment always starts and runs for at least 5 minutes (adjustable) at start-up of the unit, if the outdoor temperature so permits. If pretreatment is stopped due to a small difference between the intake temperature and the outdoor temperature, pretreatment will be blocked for 6 hours.

Configuration and settings for pretreatment


Available options & Selection


Activate pretreatment function

Configuration > Functions > Function activation


| Yes | No |

Select if pretreatment activated during free cooling during free cooling

Configuration > Functions > Pretreatment

Pretreatment active during free cooling

| Yes | No |

Activate temperature sensors

Configuration > Functions > Temperature control

Outdoor temperature sensor

| Intake air | Outdoor | Outdoor + Intake air |

Either "Outdoor" or "Outdoor + Intake air" can be used

Configure inputs and outputs

Configuration > I/O allocation settings >

Analog inputs > Outdoor temperature

Any available I/O

Analog inputs > Intake air temperature

Digital outputs > Pretreatment start

Operational settings

Data & Settings > Temperature control > Pretreatment

Activate preheater when outdoor temperature <

[8] oC

Temperature values for starting and stopping

Activate precooler when outdoor temperature <

[19] oC


[1] oC

Min difference between outdoor and intake air temperature

[1] oC

Settings only active if both intake and outdoor sensors are in use

Pretreatment block time if difference below min

[6] h

Min run time

[5] min