Functional description

The volume flow controllers work without an external power supply.

A damper blade with low-friction bearings is adjusted by aerodynamic forces such that a set volume flow rate is maintained within the differential pressure range.

The aerodynamic forces of the airflow create a closing torque on the damper blade.

The bellows extends and increases this force while at the same time acting as an oscillation damper.

The closing force is countered by a leaf spring. As the differential pressure changes, the leaf spring adjusts the position of the damper blade such that the volume flow rate is maintained almost exactly.

Efficient commissioning

The volume flow rate setpoint value can be set quickly and easily using the pointer on the external scale; no measurements are required.

The advantage over flow adjustment dampers is that there is no need for repeat measurements or adjustments by an air conditioning engineer. Should the system pressure change, e.g. by opening or closing of duct sections, the flow rates in the entire system will also change if flow adjustment dampers are used; however, this is not the case with mechanical self-powered volume flow controllers A mechanical self-powered controller reacts immediately and adjusts the damper blade such that the set constant volume flow rate is maintained.

Order example: VFC/100/E03

Installation and commissioning

• Any installation orientation
• Take the adjustment value from the characteristic on the sticker (on each volume flow controller)
• Volume flow rate setpoint can be set on external scale

Upstream conditions

The volume flow rate accuracy ΔV applies to a straight upstream section of the duct. Bends, junctions or a narrowing or widening of the duct cause turbulence that may affect measurement. Duct connections, e.g. branches off the main duct, must comply with EN 1505. Some installation situations require straight duct sections upstream.

Free air intake only with a straight duct section of 1D upstream.

Space required for commissioning and maintenance

Sufficient space must be kept clear near any attachments to allow for commissioning and maintenance. It may be necessary to provide sufficiently sized inspection access openings.

Space required

Prinipal dimensions

ØD [mm]

Outer diameter of the spigot

L [mm]

Length of unit including connecting spigot

L₁ [mm]

Length of casing or acoustic cladding

m [kg]

Weight

Acoustic data

f_m [Hz]

Octave band centre frequency

L_PA [dB(A)]

A-weighted sound pressure level of air-regenerated noise of the CAV controller, system attenuation taken into account

L_PA1 [dB(A)]

A-weighted sound pressure level of air-regenerated noise of the VAV terminal unit with secondary silencer, system attenuation taken into account

L_PA2 [dB(A)]

A-weighted sound pressure level of case-regenerated noise of the VAV terminal unit, system attenuation taken into account

_qvnom [m³/h] and [l/s]

Nominal volume flow rate (100 %)

• The value depends on product type and nominal size
• Values are published on the internet and in technical leaflets, and stored in the Easy Product Finder design software.
• Upper limit of the setting range and maximum volume flow rate setpoint value for the CAV controller

qv [m³/h] and [l/s]

Volume flow rate

ΔV [± %]

Volume flow rate accuracy in relation to setpoint (tolerance)

Δp_st [Pa]

Static differential pressure

Δp_st min [Pa]

Static differential pressure, minimum

• The static minimum differential pressure is equal to the pressure loss of the CAV controller when the damper blade is open, caused by flow resistance (bellows, crossbar)
• If the pressure on the CAV controller is too low, the setpoint volume flow rate may not be achieved, not even when the damper blade is open
• Important factor in designing the ductwork and in rating the fan including speed control
• Sufficient duct pressure must be ensured for all operating conditions and for all controllers, and the measurement point or points for speed control must have been selected accordingly to achieve this

Galvanised sheet steel

• Casing made of galvanised sheet steel
• Parts in contact with the airflow as described for the product type
• External parts, e.g. mounting brackets or covers, are usually made of galvanised sheet steel