External weather louvres are externally mounted air transfer devices for the fresh air and exhaust air of airconditioning systems. They are installed in external walls and façades. Their narrowly arranged blades give goodprotection against the direct ingress of rain as well as against leaves and birds.
Under certain unfavourable conditions, such as heavy rain, and depending on the airflow velocity it might happenthat slight quantities of water enter together with the air.
This is why the airflow velocity in fresh air openings should not exceed 2.5-3.0 m/s.
Multileaf dampers with external linkage can have parallel action blades or opposed action blades.
An external linkage transfers the synchronous rotational movement from the drive arm to the individual blades. Even very large multileaf dampers can be safely opened and closed with this type of linkage.
Opposed action blades close at different speeds since the linkage includes a transverse link. This facilitates theclosing process and reduces the closed blade air leakage.
Combinations of external weather louvres and multileaf dampers as a protection against the direct ingress of rain, leaves and birds, and for shut-off and control