Good design and installation practice for insulated flexible ducting.

  Typical Plenums standard duct sizes supplied plus highlighted in yellow some manufacturers standard sizes for guidance (please select for application).

 

Fan Coil Capacity kw

1 duct

2 ducts

3 ducts

4 ducts

1.5 – 2.5kw

250mm dia.

200mm dia.

150mm dia.

150mm dia.

3.0 – 4.0kw

250mm dia.

200mm dia.

150mm dia.

150mm dia.

5.0 – 5.6kw

300mm dia.

200mm dia.

160mm dia.

160mm dia.

6.7 – 8.0kw

355mm dia.

250mm dia.

200mm dia.

160mm dia.

9.0 – 12.5kw

450mm dia.

315mm dia.

250mm dia.

200mm dia.

14kw

450mm dia.

355mm dia.

300mm dia.

250mm dia.

20kw

500mm dia.

400mm dia.

355mm dia.

315mm dia.

25kw

560mm dia.

450mm dia.

355mm dia.

355mm dia.

 Steps to selecting plenums and grilles suitable for your application (use your scroll up/down and side to side buttons to view the full range of options).

1) Decide from the table below (taken from the Plenums “Grille Selection Data” spreadsheet which criteria your application refers to.

 Noise data

 

2) Note the yellow column with “Max. req. spigot velocity to grilles” figure in the corresponding column and match this speed to the velocity speed column on your particular fan coils options based on your design running fan speed of high or low. This then gives you the corresponding duct/spigot sizes you require.

3) Our grille selection packages are based on general office applications with 1.5-2.5kw suitable for small offices. If you require a different application please look at our “Grille Selection Data” spreadsheet and pick the noise levels and air throws suitable for good air distribution to your room.

 4) For the return air applications we have also provided various options. The standard return air plenums utilise the manufacturers standard filter supplied with the unit, if there is no filter supplied then we have provided an option with the reference + FK at the end which includes for our own filter to be included. If you require this filter option anyway so you don’t have to purchase the manufactures extra filters please contact us for a price or you can use the eggcrate return air grilles with in built filters.

 5) The return grille range has been designed to compliment the supply air range so they can either match or the eggcrate grilles with or without filters can be installed along side any of the supply air grilles.

6)  General guide lines for good design and flexible ducting installation.

  • Air volumes for general offices should be between 3-4 m/s as detailed within our individual price lists.
  • Do not exceed the manufacturers maximum fan pa (resistance), plenums grille kits and duct sizes have been selected with this in mind as long as the ductwork is installed correctly as below.
  • If you are installing mainly short lengths of insulated flexible ducting (2-5m) it must be free from kinks. Flexible ducting must always be fully extended, supported regularly ie. with hanging straps min. 25mm wide at 1m centres to keep duct sag to a minimum.
  • Flexible ducting must not be “stressed” on final connections.
  • Keep flexible ductwork away from sharp objects which may puncture it and hot un-insulated pipe work.
  • The graph below illustrates flexible duct losses (pressure in pa per m), this can be 200% or more if the ductwork is not fully extended and free from kinks.

  Flexi duct pressure losses

  • If longer duct runs are required we would recommend spiral or rectangular ducting be used sized to suit the application with added insulation.