Swirl Diffuser Type ‘FD’


Circular and square ceiling swirl diffusers that create high induction levels, for high room air change rates

  • Nominal sizes 300, 400, 500, 600, 625
  • Volume flow rate range 9 – 235 l/s or 31 – 846 m³/h
  • Diffuser face made of galvanised sheet steel, powder-coated
  • For supply and extract air
  • For variable and constant volume flows
  • For all types of ceiling systems, and with an extended border also suitable for freely suspended installation
  • High induction results in a rapid reduction of the temperature difference and airflow velocity
  • Air change rates of up to 35 per hour can be achieved by arranging several diffusers in a row with a minimum pitch of 0.9 m (centre line to centre line)
  • Ideal for comfort zones

Optional equipment and accessories

  • Exposed diffuser face available in RAL CLASSIC colours
  • Plenum box with cord-operated damper blade and pressure tap

Product Information


  • FD-Q: Square diffuser face
  • FD-R: Circular diffuser face
  • FD-*-Z: Supply air
  • FD-*-A: Extract air



  • H: Horizontal duct connection
  • V: Vertical duct connection
  • X: Flexible plenum box FLEXTRO


Parts and characteristics

  • Circular or square diffuser face
  • Diffuser face with radially arranged fixed air control blades
  • Plenum box for supply air, with an optimised equalising element that ensures a uniform airflow through the diffuser face
  • Simple installation of the diffuser face due to central fixing screw with decorative cap
  • Damper blade for volume flow rate balancing (optional)



  • M: Damper blade for volume flow rate balancing
  • MN: Pressure tap and cord-operated damper blade for volume flow rate balancing with the diffuser face in place



  • Lip seal


Construction features

  • Spigot suitable for circular ducts to EN 1506 or EN 13180
  • Spigot with groove for lip seal (if accessory lip seal has been ordered)


Materials and surfaces

  • Grille face made of galvanised sheet steel
  • V, H: Plenum box and cross bar made of galvanised sheet steel
  • X: Plenum box made of plastic and galvanised sheet steel
  • Lip seal made of rubber
  • Diffuser face powder-coated RAL 9010, pure white
  • P1: Powder-coated, RAL CLASSIC colour


Standards and guidelines

  • Sound power level of the air-regenerated noise measured according to EN ISO 5135



  • Maintenance-free as construction and materials are not subject to wear
  • Inspection and cleaning to VDI 6022

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