Modern Building Services

MODERN BUILDING SERVICES FEBRUARY 2023 27 To read the full guide ‘Give a Fan a Chance’ visit: https://tinyurl. com/4m97aen4 When bends occur in the ductwork near centrifugal fans, it’s important to ensure that the bend ‘rotates’ in the same direction as the impeller. The use of splitters within the bend can help prevent spinning in the airflow. 3. Look for pressure recovery at fan outlets (See Figures 3 and 4) The fan system’s total pressure can be reduced by using a correctly designed discharge diffuser adjacent to an axial or centrifugal fan’s outlet, when used in a non-ducted outlet system, at a 15 degree or less angle. This arrangement can also reduce discharge losses by up to 75 per cent for both fans, increasing the IAQ level. 4. Do not block fan inlets or outlets (See Figures 5 and 6) You should allow a gap that is at least equal to one fan diameter between the fan’s intake and any near obstructions. However, it should be noted that even doing this can cause the fan’s performance to be less than rated. When an inlet is obstructed, the impeller can be starved of air, which in turn increases the system’s resistance and reduces airflow being handled by the fan. This applies to all fan types. Additionally, you should always fit an inlet cone on open axial fan inlets. When placing a fan, you should allow a gap of at least one fan diameter between the fan outlet and any obstruction and fit a diffuser on the discharge. When the discharge is too close to a wall the obstruction can generate noise and increase discharge losses. Efficient ventilation relies on good installation As more and more people become attuned to their surroundings and the air they breathe, it is vital that all measures are taken to guarantee the highest level of efficiency in ventilation systems. To support installers in achieving good IAQ levels, Elta Fans has collated a comprehensive ventilation dos and don’ts guide titled ‘ Give a Fan a Chance’ . Broken down into five sections, the guide details installation tips for axial, centrifugal and roof Fans before delving into the topics of noise and vibration reduction. Figure 2. For centrifugal fans, it’s important to ensure that the bends near ductwork ‘rotates’ in the same direction as the impeller Figure 3. Pressure recovery with centrifugal fans Figure 4. Pressure recovery with axial fans Figure 5. Blocking axial fan outlets can increase noise and discharge losses Figure 6. Blocking axial fan inlets can lead to the impeller being starved of air Figure 1. For centrifugal fans, uniform air entering the inlet is important to prevent air spin Source 1 https://workplaceinsight.net/ poor-indoor-air-quality-is-a-threat- to-health-say-people-coming-into- the-office/ FEATURE INSTALLER’S VIEW