9
10
OIMM – VENTUS PRO
With the outlet connected to the discharge duct by a flexible connector, which is desirable for noise and vibration
isolation, it is important that the connector is correctly fitted. The fan outlet and the duct should not be misaligned
nor should the flexible connector be allowed to concertina. A smooth passage of air is desirable at all times.
When discharging into a duct of larger cross-sectional area than the fan outlet, an expansion section with an
included angle of 7-20
º
should be used. The ideal configuration is with parallel length
of ducting prior to the expansion section, allowing the air to become less turbulent before expanding. The fan
should never discharge directly into a duct with larger cross- section.
The same criteria apply when discharging into a duct of smaller cross-sectional area then the fan outlet.
A ducting section with an included angle of up to 45
º
should be used. Losses will again be minimized if a parallel
section of ducting is used prior to the reducing section. To achieve ideal conditions the length of parallel ducting
in both cases should be equal to 8 impeller diameters. However, parallel ducting of considerably shorter lengths
can be used to advantage.
!
Appropriate operation of the flexible connection occurs if it is stretched to about 110 mm.
!
The ducts connected to the AHU have to be suspended or underpinned with dedicated support
elements. Conducting the ducts with the fittings should be done in a way to eliminate possible
increase of noise level in the ventilation system.
!
Air tightness should be maintained to achieve required air flow conditions. Poor ductwork
connections to the unit and incorrect size, shape and arrangement of ductwork fittings can
change airflow conditions.
!
DUCTED OUTLE CONNECTIONS
3.6.1
»
DUCTED OUTLET CONDITIONS
»
RULES DUCTED OUTLET CONNECTIONS
Extremely high losses occur when attempts are made to change the direction of the airflow close to the fan
discharge. If this is necessary the installation should be carried out as in and ever as in. A better solution is to
have a parallel section of ducting prior to changing direction and it should be as long as can be accommodated.
