Why Multiple Fan Array Configurations & FanWalls are Advantageous

What is a Multiple Fan Array?

A multiple fan array is exactly as it sounds, instead of running a large single belt drive as the work horse of the ventilation system, multiple fans are used in parallel to one another. This can be any configuration that is needed to achieve the overall system duty.


Multiple Fans in Parallel vs. a Single Fan in Ventilation Systems

Running more than one fan running in parallel on a fan grid (or fan wall) in a ventilation system can be advantageous for a number of reasons as indicated below:

1. Efficiency
Typically 40% of a commercial buildings energy use comes from heating, ventilating and cooling with 50% of the HVAC energy consumption coming from fans. Given the increasing cause for environmental concern, designers should look to select EC plug fans which will not only provide the necessary reliability, but also provide optimum efficiency and environmental benefits. Savings as a result of moving from AC to EC occur from both improved motor efficiency and optimising system design. There is potential to achieve greater efficiency when the system’s operating range includes multiple plug fans running closer to their peak efficiencies, instead of one large fan controlled over a wide operating range.


2. Redundancy
Continuous and consistent airflow is essential to virtually every facility. Running fans in parallel allows for redundancy which is designed to improve reliability and consistency. For example, if one fan fails within the ECFanGrid (multiple fan wall from Axair), only that portion of the airflow is lost, unlike single fan systems where the entire air handler goes offline. Moreover, the loss of airflow from one plug fan can be offset by increasing the speed of the remaining fans; this can be achieved automatically in conjunction with the building’s management system.


3. Flexibility
The number of plug fans in each ECFanGrid or fan wall system can vary according to the airflow requirements. For example, in a wall of 9 fans in a 3×3 configuration where only 7 fans may be required for normal operations to deliver the designed duty, the 8th and 9th space can be blanked off with a plate. If the demands on the AHU increase through building expansion for example, the blanking plates can be removed and 1 or 2 fans added to the grid to meet the new requirements.


4. Ease of installation
ECFanGrids are ideally suited for retrofit AHU projects, particularly where a single large radial fan is being replaced. It is often the case that buildings have expanded around an AHU over its years of operation. This can make the extraction of the old fan problematic but the install of the new fan impossible without minor works to the fabric of the building. Plug fans can be walked through standard pedestrian doorways by no more than two operatives: a significant factor in maintaining a tight replacement schedule, reducing costs and downtime.


5. Ease of maintenance
Unlike a traditional belt drive unit which covers a large floor space, the ECFanGrid is completely free of the floor. This means that maintaining the hygiene of the AHU is quicker, simpler and more effective. No dust is released into the supply air as there are no belt drives to degenerate over time. Furthermore, component failure is quickly dealt with due to the modular nature of the ECFanGrid. For example, a single fan module could be replaced and the AHU back online within an hour of being shut down.


6. Noise Attenuation
Case studies show that there is the potential to significantly lower noise when using an ECFanGrid. There are two major advantages to attenuate noise. First, the noise spectrum of smaller impellers contains higher frequencies, thus the wave lengths are shorter, allowing for the use of shorter attenuators. Second, the required length of the fan section in a typical air handling unit using a single large radial fan can be reduced dramatically, in some cases up to 50%. Read more about noise in fan systems here.


7. Easy to Scale up Capacity
Multiple fan arrays offer the flexibility of being able to quickly and easily scale up the duty if required by adding additional fans to the array. Let's say for example a current array has a 3x3 grid but has two blanking plates as at the time that capacity was not needed, therefore the expense of the fans didn't warrant adding them in. When the time is right to scale up, instead of replacing the entire system, one or two additional fans can be added to the blanked areas to quickly add more performance to the ventilation system. Equally, as it's only fabrication metal work that's needed to extend it further, and everything is delivered in transportable and carried by max two persons, this can be added on reasonably fast with no downtime of the existing system.


The multiple fan configuration can be used in numerous applications due to its adaptability. Our ECFanGrid case study booklet features several examples of retrofitted multiple fan arrays that replaced large single fans in air handling units (AHUs). The different sizes and configurations highlight the flexibility of our Rosenberg fan array solution; the ECFanGrid.


If you would like us to specify an ECFanGrid for your application, please call 01782 349 430 or email us at [email protected].