Chapter 3

3.2.8 Variable volume control

A variable volume controller, VAV controller or VVC, is used in a ventilation system to measure and automatically control flow rates based on an external value, such as CO2, temperature, presence, etc. When the measured value changes, the position of the valve blade is automatically adjusted so that the flow rate changes.

Material quality and thicknesses
For normal comfort ventilation, variable volume controls are manufactured from the following materials:

  • Casing: Sendzimir galvanised steel;
  • Valve blade: Sendzimir galvanised steel, with rubber sealing ring;
  • Other choice of material, depending on the application, in consultationwith the supplier.

The variable volume control is available with circular and rectangular connections.

The available nominal dimensions of the intermediate variable volume controls are standardized to NEN-EN 1505 (rectangular connections) and NEN-EN 1506 (circular connections) and can be selected as indicated in the tables for standard dimensions given in this guide under chapters (rectangular connections) and (circular connections). They refer to the internal dimensions with a tolerance of +0 to -5 mm. The dimensions depend on the manufacture.

Inspection possibilities
It should always be possible to inspect intermediate variable volume controls for operation and valve position (this can usually be checked from the outside).

Assembly instructions
Variable volume controls must be installed according to the manufacturer's instructions. If present, they must at least comply with the requirements of section 3.1.4.
A minimum distance from or to a bend, fan, valve, etc. must be taken into account. This distance differs per supplier.
If there is no clear specification by the supplier, a minimum distance of 1 to 2 times the connection diameter is recommended for circular variable volume controls.
For rectangular variable volume controls, a minimum distance of 1 to 3 times the duct width is recommended (depending on the desired measurement accuracy; the greater the distance, the higher the measurement accuracy).

The housing of the variable volume control is also available with factory-soundproofing.

Sustainability aspects
Variable 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 accessories have sufficient airtightness in accordance with NEN-EN 1751.
The VAV principle is applied to save energy. The air volume, and thus the required energy consumption of the air handling system, is determined on the basis of the demand from the building or space.

Variable volume control

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