Replacing the filters of a controlled mechanical ventilation (HRU) system is a simple operation, but it requires some preliminary steps: identifying the filter section and the direction of the airflow.
In a classic double-flow HRU, the filter sections are generally two: one for supply and one for exhaust. In some models, return filters and grille filters are also present, which are easy to identify.
Optimal configuration:
- Supply filter: high efficiency, to protect occupants from fine particulate matter.
- Exhaust filter: lower efficiency, to prevent coarse dust from depositing on the heat exchanger and compromising its performance.
Recommended maintenance frequency:
- Filter replacement: once a year, or more frequently if the pressure drop is excessive.
Steps for replacement:
- Identify the filter sections and determine which is the supply and which is the exhaust. The supply filter is usually much dirtier than the exhaust one.
- Remove the saturated filters and observe which side has accumulated more dust: that is the air inlet side. New filters must be inserted respecting the airflow direction. Some filters have directional arrows to facilitate positioning.
- If the filters were removed without noting their orientation: it is possible to deduce the air inlet side by observing the position relative to the heat exchanger, which is always located at the center of the main unit. Air always moves toward the exchanger: therefore, the air inlet side is facing the outside of the unit.
- Once the correct position has been identified, insert the new filters.
Other components to maintain:
- Grilles and vents: periodic cleaning
- Heat exchanger: replacement every 10 years