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Rules to follow when installing an MEV system


First, the installation of a Mechanical Exhaust Ventilation system, or MEV, must be done by a qualified technician. In addition to the information in this article, it is necessary to refer to the manufacturer’s manual for further information.

Improper installation may result in deterioration of the mounting bracket, noise nuisance in case of vibration of the MEV fan, or reduced fan performance.

MEV installation -Advice category page

The location of the MEV

  • The location of the MEV fan must be considered before installation. In the case of installation of an MEV, it is necessary to insulate any ducts placed outside the heating zone to avoid condensation accumulating in the ducts.
  • To obtain a more homogeneous ventilation system between rooms, it is preferable to have the same length of duct between the ventilation unit and the extraction ducts. Ideally it should be as close to the kitchen duct as possible.
  • Most MEV fans can either be suspended from the structure of a house by cords or other suspension system, or be directly attached to the wall. In the case of a wall installation, some MEVs are sold with placement templates. For example, the V4A has a base to precisely identify where the mounting screws are to be placed.
MEV installation -Advice category page

How should an MEV be connected?

To make the electrical connection of a humidity-controlled MEV, it is essential to comply with the rules in force in the country where it will be installed. Regardless, several rules still apply.

  • Firstly, it is necessary to have a dedicated electrical line at the electrical panel with a circuit breaker. The electrical panel must also include a 30 mA differential circuit breaker at the head end of the line.
  • For the electrical connection between the MEV unit and the electrical panel, a 1.5 mm² wire should be used. The colour code below must be respected (at least for the earth):
    – Live: Red
    – Neutral: Blue
    – Earth: Green/Yellow

The schematic diagram here aside shows the typical installation of an MEV installation.

MEV installation -Advice category page

Avoid nuisances

  • If the ventilation unit is placed directly on the wall, silent blocks must be inserted between the wall and the mounting points of the unit to avoid the possibility of vibrations generating noise that can disturb the occupants. For example, vibrations may be felt during the night if the ventilation unit is installed too close to the bedrooms.
  • Depending on the layout of the MEV sytem, it is possible to install attenuators with the ventilation box. This ensures very low nuisance at the exhaust unit. This can be particularly useful for small open plan studios where the kitchen is open to the bedroom/living room.
  • In the case where flexible ducts, expandable or not, are used during installation of the MEV, it must be ensured that they are neither too loose or too taught. Acoustic problems can also be generated if the manufacturer’s recommendations for the angles of the bends in the duct network are not observed.
MEV installation -Advice category page

The products choice

  • The diameter of the duct must also be suitable for the flow passing through it. In France, it is common to have a 125 mm diameter duct for the kitchen extraction air duct and one or more ducts of 75 or 100 mm for the bathroom duct and that of the toilets.
  • The choice of humidity-controlled exhaust units must be made taking into account current technical recommendations. The technical appraisal refers to the type of vent adjustment needed within a room to ensure good air quality while reducing extraction rates.
MEV installation -Advice category page

Technical recommendations

  • It is necessary to check that the door undercuts ensure free circulation of air from one room to another. In general, the undercuts must be between 1 and 2 cm across the entire width of the door.
  • Finally, the last point to consider when installing an MEV is the roof discharge, which must be suitably sized. It must be positioned far enough from the air inlets not to create a phenomenon of air recycling. In addition, the regulations prohibit any discharge of exhaust air in attics.

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