The remit of a facilities manager means they are invariably masters of many trades. For core building services, such as ventilation, they require an understanding of the range of variables that dictate specification, installation, and ongoing maintenance. David Millward, Group Product Manager at Elta Group, provides some top tips for retrofitting a fan.
Indoor air quality (IAQ) is finally being acknowledged as a critical component of building management. This has led to a greater focus on ventilation, especially as public spaces continue to return to full occupancy levels. Whilst previous strategies may simply have relied on natural ventilation, such as opening windows, there is now an awareness that more sophisticated solutions are required to provide healthy air.
With this improved understanding comes an even greater challenge for facilities managers who are tasked with delivering suitable volumes of airflow in a building, all the while considering other key factors. The importance of finding the balance between flow rates and ambient temperature is well documented, which is where the latest technology is designed to utilise heat exchange to minimise running costs.
However, there are also some practical steps that facilitates managers should take to ensure ventilation systems are operating at maximum effectiveness. Much of this comes down to the fan itself, which makes specifying, positioning, and maintaining it key to providing good IAQ.
Axial Vs Centrifugal Vs Mixed Flow
Two common types of fans are axial and centrifugal, and it is worth getting to grips with what each type provides in order to ensure the optimum choice is made. While the vast majority of ventilation contractors are experienced enough to know whether an axial or centrifugal fan is most appropriate, it is still useful for facilities managers to have an understanding of the distinction.
Axial flow fans are typically compact, easy to install, and competitively priced. As a result of design improvements, they can also offer higher efficiencies and lower noise levels than previous incarnations and are suitable for a multitude of applications. Crucially, air flow is straight through the fan i.e., in an axial direction.
Centrifugal fans impart energy on the air in a way that causes it to flow in a radial direction. They typically give higher pressure development than axial fans and can either be forward curved or backward curved.
In addition, it is also worth noting mixed flow fans. These fans take advantage of axial flow fan features like volume flow and axial direction of airflow, whilst also incorporating features from backward-curved centrifugal fans, such as pressure development. The final product compares favourably to the axial flow fan for efficiency, noise and pressure development and to the centrifugal fan for airflow and compactness.
Ensuring the correct fan is used for the requirements of a particular location is important, as it helps to improve the overall effectiveness of a system. Facilities managers know the unique requirements of a premises better than anyone, which is where an open dialogue with contractors and building designers is key to improving existing systems.
Positioning Of The Fan
Another factor in determining the operational efficacy of a fan is where it is located. Once more, a detailed understanding of building layout, including which rooms are likely to be busier at certain times, will be integral to optimal ventilation positioning.
For instance, it may be that the most appropriate solution is a roof fan, which is specifically designed to deliver ventilation through roof outlets. The range includes models designed to offer high levels of volume flow or pressure in axial, centrifugal or mixed flow configuration.
For internal locations, care should be taken to allow a gap equal to one fan diameter between the fan intake and nearby locations. Otherwise, the impeller can be starved of air, which has the effect of increasing resistance and thereby reducing the air flow being handled by the fan.
Noise And Vibration Control
Performance and efficiency are always going to be the most important factors for facilities managers to consider, but issues such as noise or vibration should also be accounted for. Ensuring that neither of these are too disruptive to building occupants is important in providing a usable and comfortable space.
Sound, for example, cannot be avoided – but it can be minimised or reduced. Airborne and duct-borne noise can be reduced by using attenuators, while structure-borne noise can be limited by isolating the fan from the structure or the duct itself. Using lined fan types and duct lining can also alleviate breakout of duct-borne noise.
Vibration is another inevitable side-effect, as the fan will cause the structure on which it is mounted to vibrate. To overcome this, vibration isolators should be selected to offer the minimum deflection required. They should also be suitable for the fan and environment in which it will be operating.
Ongoing servicing and maintenance is something that facilities managers will be all too aware of, across all types of equipment. Ventilation is no different, and regular checks on a system will help to keep IAQ as high as possible.
Maintenance schedules vary depending on the type of fan being used, the atmosphere in which it is operating, and a range of further variables. Those tasked with the upkeep of such systems should check with the manufacturer, and formulate a detailed maintenance schedule.
Given their responsibility in providing a comfortable, safe, and healthy building, facilities managers should be aware of the importance of delivering good IAQ. This means keeping abreast of the key technologies in ventilation design and ensuring that the factors outlined above are considered when making improvements to existing systems.
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