The impeller is an executive element, an absolutely necessary element of any HVAC system, converting the rotational movement of the rotor of the electric motor into the translational movement of air for its forced (with rapid heat transfer) convection in the room and in the heat exchangers of the unit. The consumer parameters of the entire installation largely depend on its correct calculation, high-quality manufacturing, integrity, balancing and cleanliness:

• efficiency (efficiency of conversion of electrical energy);
  
• direction of air flow;
  
• vibration and noise characteristics;
  
• engine bearing wear, etc.
  

With a huge variety of sizes, shapes, materials and manufacturing technologies (cast, stamped, welded, riveted), fan impellers are divided into two main types: axial and radial. The former form a flow axial with the shaft on which they are installed, they are most efficient, but they require an exceptionally round channel - in any case, in a section with a length at least slightly exceeding the axial size of the impeller. The latter throw air radially (or rather, tangentially) in the plane of rotation, which allows you to create fans, fan coil units and split systems that are as flat as possible, meeting modern technical and aesthetic requirements.