Abstract: A centrifugal fan arrangement includes a centrifugal fan rotatably mounted within a scroll housing and a plurality of circumferentially spaced fan blades fixed to a central fan axle extending along an axial direction and/or to a circumferential fan ring extending in a plane orthogonal to an axial direction. The scroll housing includes a housing main portion with a maximum housing diameter D and a maximum axial housing width H, a housing inlet portion and a housing outlet portion, said housing main portion surrounding said centrifugal fan at radially outer locations to define a circumferentially extending air guiding space. The housing inlet portion is located at radially inner locations to define an inner air inlet space. The housing outlet portion is located at a radially outer location to define an air outlet space.

Abstract: A heat recovery unit with a unit housing (11) defining a unit compartment, a heat exchanger (20), a fresh air bypass flow passage and/or an exhaust air bypass flow passage, a fresh air centrifugal fan arrangement (41) and an exhaust air centrifugal fan arrangement (42), a fresh air filter (51) and an exhaust air filter (52).

Abstract: The invention relates to a ventilation unit (1) for providing supply air (SA), preferably outside air (OA) or fresh air, to an apartment or parts thereof and for removing return air (RA), preferably exhaust air (EA) or used air, from said apartment or parts thereof. The ventilation unit comprises a bypass valve (BV; BV?) having a plurality of elongate members (EM; EM?) extending across a bypass duct and arranged in parallel next to each other, thus forming an arrangement of a plurality of elongate members next to each other as a one-elongate-member-thick layer. At least some elongate members (EM; EM?) of said plurality of elongate members (EM; EM?) are rotatably mounted around an axis of rotation (AR) parallel or identical to a longitudinal axis (LA) of said elongate members (EM; EM?). At least some elongate members (EM; EM?) are rotatable between a first rotational position or closed position (CP) and a second rotational position or open position (OP).