Defrost settings

This section describes making the following defrost-related settings:

  • Defrost. method — The defrosting method is applied by the unit when the heat recovery cell must be defrosted. The heat recovery cell is defrosted by using the heat recovered from the extract air, or by bypassing the heat recovery cell from the outside. The duration of the defrosting cycle is 15–45 minutes depending on the amount of ice. Defrosting is part of the normal operation of the unit in winter.
  • Internal %RH — The relative humidity of indoor air affects the frosting of the heat recovery cell significantly. The unit is designed to operate optimally in normal humidity conditions of residential buildings. If the unit has been installed in exceptional humidity conditions, such as pool premises, the relative humidity of air coefficient may need to be manually adjusted. Set the humidity percentage above zero in humid conditions and below zero in dry conditions.
  • Outdoor air °C — The outdoor air temperature parameter can be used to control the operation of the unit in very cold conditions below -20°C when using an aluminium cell and below -5°C when using a plastic cell). The parameter has been optimised based on the cell type used and the installation conditions.
    Important:

    The outdoor air temperature setting must only be changed in extreme situations, and with the help of a HVAC specialist. If the heat recovery cell becomes frozen, the temperature value must be lowered. We do not recommend that the value be increased under any circumstances.

To make the aforementioned settings:

  1. Select Expert settings.
  2. Defrost settings are described in the Defrost settings area.
  3. Select one of the following defrosting methods from the Defrost. method drop down menu.

    • HR cell bypass — In this defrosting method, the heat recovery cell is bypassed on the supply air side. This does not change the ratio between the supply and extract air flows. In some cases, this prevents the generation of a potentially harmful underpressure in the apartment.

      In this defrosting mode, the electrical resistor heats the cool air flowing in from outside to the set temperature for the duration of the defrosting cycle. If the set temperature is too high compared to the outdoor temperature, the unit reduces the supply and extract air flows in order to achieve the set supply air temperature.

    • Supply fan stop — In this defrosting method, the supply air fan will be stopped for the entire defrosting cycle. A momentary underpressure is created in the apartment.
    Important:

    The parametres need not be changed in normal living conditions. Exceptional conditions include high moisture loads caused by e.g. pool premises, or the accumulation of a problematic amount of ice in the exhaust air channel.

    The defrosting method is now set.
  4. Set the relative humidity of air by moving the blue indoor%RH slider to the desired value.

    The relative humidity of air value can be set between -50 % – +50 % RH.

  5. The relative humidity of indoor air is now set.
  6. Set the outdoor air temperature by moving the blue Outdoor air °C slider to the desired value.

    You can set a value between 0–100%. The factory setting depends on the type of the ventilation unit.

  7. The outdoor air temperature is now set.