Flexible Duct

Supports


  • Flexible duct hangers or saddles in contact with the flexible duct in accordance with Clause 2.5.3 of AS4254.1 must:
  • Be a minimum width of 25mm.
  • Have semi-rigid, fire resistant, load distributing support material with a minimum width of 75mm for at least a quarter of its circumference.


Flexible duct support must be spaced in accordance with Clause 2.5.3 of AS4254.1:

  • No greater than 1500mm apart
  • With no greater than 40mm/m of sag per support.

Connections


  • Flexible duct must be:
  • Cut to length when less than a full length is required, N.B. excess removed.
  • A single length of 6 m maximum. No intermediate joins are permitted. (Classes 4 to 9)
  • Not more than two lengths of up to 6m (Classes 1 to 3)
  • Attached to spigots preferably of min 150 mm in length.
  • Where duct tape is used as a sealing media, it must be:
  • Minimum 0.15 mm thick and 48 mm wide
  • Minimum of three overlapping wraps adhered to a collar on an air terminal device as outlined below.
  • Where mechanical fixing is used, it must be fastened permanently to circular collars on air terminal devices by means of a drawband/banding system located over the top of the air seal.
  • Vapour seals (where required) are to be continuous and any tears patched/taped up

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Labelling


  • Labels on the outer jacket/sleeve of all insulated flexible ductwork in accordance with Clause 2.7 of AS4254.1 must:
  • Be repeated along the total length of the ductwork at 1000 mm intervals
  • Include the following information:
  • Name of manufacturer
  • Compliance with AS 4254.1
  • The R value of the flexible duct.

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Changes in Direction


  • Flexible duct work must extend straight for 100 mm from the connection to an air terminal device prior to any change of direction.
  • Flexible duct work must be installed with a minimum bend radius to flexible duct diameter of 1 to 1.
  • Nude core (uninsulated) duct is only be used for exhaust systems such as toilet, general and miscellaneous exhausts, never for bathrooms, laundries or similar steam generating areas.