Leaf Ventilation Module

The Leaf Ventilation function block controls a Leaf Ventilation unit based on Humidity, Temperature, and CO2 levels. When using a Motion detector, different ventilation operating speeds can be defined dependant on presence detection. If desired, various special functions such as Sleep, Turbo, and Exhaust Air can be activated via the User Interface as well as via function block inputs. If several Leaf units are in use, these can simply be linked via the module properties. A distinction is made between Type A and Type B fans. This differentiation enables the fans to operate in opposite directions. This means that if Type A fans provides a fresh air supply then Type B fans will exhaust air.

An imbalance in the distribution between type A and B fans can lead to vacuum/over-pressurisation in the room! If air-dependant fireplaces are in the fan’s area of influence, a negative pressure can draw smoke into the living area!



AbbreviationDescriptionUnitValue Range
HiInternal Humidity. If humidity exceeds parameter Hmax, the ventilation will increase. If this input is not connected, humidity is not taken into account.%0…100
CO2Internal Air Pollution. If CO2 levels exceed the parameter CO2max, ventilation is increased. If this input not connected, air pollution is not taken into account.ppm0…∞
TsOutside Air Temperature. Indicates the temperature of the incoming air. Used for Temperature functionality. If this input is not connected, the value of the System Variable “Outside Temperature” is used. If this is also not available, all Temperature Functionality is disabled.º
IwDigital Input – Window Contact (ON: Window open, OFF: Window closed), if window is open Ventilation is deactivatedDigital0/1
MvMotion Sensor Input. The overrun duration must be configured using parameter TH.Digital0/1
StSTOP. Stops the Fan and closes the Ventilation flap when ON.Digital0/1
SIDigital Input – Sleep Mode: Turns off ventilation for the time set in parameter TSl. Afterwards, the block will start again with ventilation.Digital0/1
TbBOOST. Stops all control and sets the output to 100 percent.Digital0/1
ExExhaust Air. Stops all control and exhausts air at 100 percent. ATTENTION: This input can only be used if the block property “Exhaust Air / Supply Air Operation Permitted” is activated.Digital0/1
RFAcknowledge Filter Change. Resets the filter warning. Should be activated after a filter change.Digital0/1


AbbreviationDescriptionUnitValue Range
AQsAnalogue Output – Value indicates which parameter is driving the ventilation. This output is for informational reasons only. 0: Basic Ventilation, 1: Increased Humidity, 2: Temperature Control, 3: Poor Air Quality (CO2), 4: Manually Stopped, 5: Window Open, 6: Manual Boost, 7: Manual Control User Interface, 8: Manual Exhaust Air, 9: Sleep Mode.0…9
QftFilter Change. Indicates whether air filters need to be changed.Digital0/1
QeError Output: Indicates whether there is an error: 0 = No Error, 1 = Offline, 2 = Stuck, 3 = Aperture Error.0…3


AbbreviationSummaryDescriptionUnitValue Range
HmaxMaximum HumidityMaximum Humidity Limit: The block tries to keep the Internal Humidity level below this value.%0…100
CO2maxMaximum Air PollutionMaximum Tolerable Air Pollution: The block will always try to keep the Internal Air Pollution level below this value.ppm0…∞
THMotion Sensor TimeoutOverrun timer, which starts with the falling edge of the motion detector. Extends presence by the specified time spans0…∞
TSlSleep Mode DurationOverrun timer, which starts with the falling edge of the sleep input. Hold the device closed for a specified period of time.s0…∞
ViAbsence Intensive VentilationIntense Ventilation During Absence. At Humidity levels above Hmax or CO2 levels above CO2max, the fan will operate at this strength. In Temperature mode, this value is used as the maximum.%0…100
VBasic Ventilation During AbsenceBasic Ventilation During Absence. Fan operates at this level in automatic mode when absent. In Temperature mode, this value is used as the minimum.%0…100
VPiPresence Intensive VentilationIntensive Ventilation During Presence. At Humidity levels above Hmax or CO2 levels above CO2max, the fan will operate at this strength. In Temperature mode, this value is used as the maximum.%0…100
VPPresence Basic VentilationIntense Ventilation During Presence. Fan operates at this strength during automatic mode when present. In Temperature mode, this value is used as the minimum.


Ventilation Direction (Without Heat Exchanger)Sets the airflow direction on a pair of Leaf fans when the heat exchangers are disabled. If the heat exchangers are active then there is no set direction since the direction is reversed in regular intervals


  • From Fan A to Fan B
  • From Fan B to Fan A
Exhaust Air / Supply Air Operation PermittedSets whether a fan is permitted to operate as extract only. When active, an extra input is available on the Leaf function block which can be used to start the extract mode. WARNING: If a room has an open fireplace an extract fan in close proximity may result in smoke being pulled into the room!
Assigned Fan A/BLeaf fans are synchronised. Whilst fan A provides fresh air, fan B operates to extract stale air and vice versa. Please ensure that your configuration always contains the same number fans set to type A and B. WARNING: An uneven split may lead to either higher / lower air pressure in a room!Device Errors

Device Errors

If you receive a message that your Leaf unit has experience an aperture error or fan motor fault, refer to the documentation on the device’s diagnostic inputs here. for more detailed information.

Maintenance Interval/Filter Change

Information on the filter change or the maintenance interval of the device can be found in the device documentation here.