The 4000-series is more or less the bigger version of the 1800-series. This air inlet valve also has a relative small width and big height. Due to this phenomenon, it is very well and easy controllable at minimum ventilation level.  At complete opening, this air inlet valve has, due to the relative big height of the inlet, a higher capacity then for example the 3000-series. The inner flap is on both sides equipped with an edge. This edge assures that at minimum ventilation level the air stream is brought straight into the house.

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