Constant Volume Swirl Diffuser (CSW, CRW3) | rickardair

Constant Volume Swirl Diffuser (CSW, CRW3)

The RICKARD Constant Volume Swirl Diffusers (CSW/CRW) have been designed to provide a cost effective outlet that provides excellent levels of comfort in an architecturally pleasing package.

CSW Constant Volume Swirl Diffuser


Damper adjustment is easily accessible via a screw driver slot in the diffuser face.


Traditional designs suffer from dumping at minimum because a butterfly damper controls volume at the inlet of a plenum and not at the outlet. Rickard limits this effect by positioning the damper closer to the outlet and uses an aerodynamically shaped back-pan instead of a plenum.

Swirl diffusion pattern creates excellent mixing.
Good Coanda, Velocity and Throw at all diffuser damper positions.
Good Air Change Effectiveness.
Good ADPI values.


Included Jubilee Clamp saves time and material when attaching the flex.
Included plastic packaging can be used to protect the Tile once installed.


Low diffuser height (125mm) can reduce a buildings overall cost by reducing the height of the ceiling void.


Available in Round (CRW) for skimmed ceilings and Square (CSW) for drop-in ceiling Tee applications.
High Quality Epoxy Powder Coated Finish available in a wide range of colours. Matt White comes as standard.


No regular maintenance is required.


The RICKARD Constant Volume Swirl Diffusers (Types CSW and CRW) are primarily intended for use in internal zones of buildings where good air mixing is required for improved occupant comfort. Normally these zones are less complex to air condition as load fluctuations are not as severe as those on building perimeter zones. The Constant Volume Swirl Diffuser, as its name implies, does not automatically regulate the air volume entering the conditioned space - they are constant volume devices. Consequently, room temperatures will vary with room loads (assuming the duct air temperature and pressure remain constant).

Should this method be decided upon, care should be taken in selection of the CSW and CRW diffusers to ensure dumping does not take place at minimum air flow status.

The Rickard CSW and CRW diffusers can be used to supply spaces that require heating or cooling. To ensure that dumping does not occur in cooling and stratification in heating care must be taken to supply the diffusers with adequate pressure.

Constant Volume Swirl Diffusers can be used to supply top up heating when required. This is achieved by fitting them with a Rickard neck heater.

Although the CSW is a constant volume terminal device, the air volume flow rate may be adjusted manually to obtain the required design air flow.  This is achieved by manually adjusting the control disc up or down using the screw driver slot located in the face of the trim.

CSW Volume Damper AdjustmentCSW Volume Damper Adjustment

The most important practical factors to consider in internal zones are noise levels and uniform air distribution without "dumping" or "coning" effects. "Dumping" is the tendency for cold, dense air to leave the diffusers as a vertical column similar to a waterfall.

The effect of dumping is to overcool the person immediately below the diffuser while the person further away will not be cooled enough.

Dumping is eliminated by ensuring that the discharge air energy from the diffuser is adequate to distribute conditioned air evenly throughout the conditioned area and at the same time provide good secondary room air induction rates. Providing the total pressure in the neck of the RICKARD CSW diffuser selected is not too low, dumping of conditioned cold air will not take place. The CSW is designed to be resistant to dumping.

In the context of radial discharge ceiling diffusers, 'coning' occurs when two air streams travelling in opposite directions meet. As a result a downward moving cone of air is produced this will have a similar effect to dumping. Coning is substantially reduced with the use of swirl diffusers, but it can be avoided completely by ensuring that CSW/CRW diffusers are placed far enough apart to eliminate drafts in the conditioned spaces. The Table CAV Swirl Diffuser Performance Data shows the distance from the centre of a CSW/CRW at which air velocity has reduced to 0.25 m/s (the 'throw' of the diffuser). Using this information, CSW/CRW diffusers should be situated in the ceiling such that two adjacent diffusers are separated by slightly less than the sum of their throws. Exactly how much less depends largely on the ceiling height and the amount of air movement desired in the conditioned spaced. If the CSW/CRW is used in conjunction with Variable Linear Diffusers or Side Wall VAV Units, their throws should also be considered.


The drawing below describes how to determine the maximum ceiling height that can be achieved from a diffuser. Please see the diffuser performance data page for airflow, throw, noise and pressure information.

150 to 300mm
150 to 300mm
CSW Constant Volume Swirl Diffuser
CRW Constant Volume Swirl Diffuser