Function
A constant volume controller, CAV controller or CVC, is used in a ventilation system to keep a fixed flow rate constant. When the system pressure in front of the controller changes, the position of the valve blade is mechanically adjusted so that the flow rate remains constant. This flow rate can be easily read and adjusted on an external scale.
Material quality and thicknesses
For normal comfort ventilation, constant volume controls are manufactured from the following materials:
- Casing: Sendzimir galvanised steel;
- Valve blade: Sendzimir galvanized steel;
- Other choice of material, depending on the application, in consultationwith the supplier.
Connections
The constant volume control is available with circular and rectangular connections.
Dimensions
The available nominal dimensions of the intermediate constant volume controls are standardized in accordance with DIN EN 1505 (rectangular connections) and DIN EN 1506 (circular connections) and can be selected as indicated in the tables for standard dimensions given in this guide in sections 2.1.1.6 (rectangular connections) and 2.1.3.6 (circular connections). They refer to internal dimensions with a tolerance of +0 to -5 mm. The dimensions depend on the manufacture.
Assembly instructions
Constant volume controls must be fitted in accordance with the manufacturer's instructions. If present, they must at least comply with the requirements of paragraph 3.1.4.
The constant volume control should be installed in a horizontal or vertical duct with the rotation axis in a horizontal position.
A minimum distance from or to a bend, fan, valve, etc. must be observed. For circular constant volume controls the minimum distance is 3 x the connection diameter. For rectangular constant volume dampers, the minimum distance is 3 x the duct width.
Sustainability aspects
Constant volume controls with circular connections, fitted with rubber sealing rings, can be connected to air ducts efficiently and make a contribution to the airtightness of the air duct system, if the fittings have sufficient airtightness in accordance with NEN-EN 1751.
