Fan Array System: How Do You Engineer It for Commercial HVAC Projects?Fan array systems (FAS) are part of a growing trend to retrofit ‘green’ HVAC solutions in commercial buildings. In 2016, McGraw Hill found that 61% of all U.S. construction projects were retrofits. Importantly, these retrofits deliver several key benefits, including energy savings. According to the Pacific Northwest National Laboratory at the U.S. Department of Energy, small offices and stand-alone retail units can make energy savings of 35% with retrofit technologies, while supermarkets can save 24%.  In cold weather climates, energy savings can even rise to 40%. Retrofits can also deliver better sustainability measurements, extend the life of your existing HVAC system, and improve its overall performance.


What is a fan array system?

Fan array systems are a combination of smaller fans built into a single wall. Typically, they replace a traditional large, belt-driven fan. A series of smaller fans (an “array”) take the place of inefficient air handlers (AHUs). These motorised impellers operate in parallel. An obvious visual difference with fan array systems is their dramatically shorter footprint. They also provide strong energy performance for each selection point, with three different selection modes available in Swiss Rotors’ new model – economical, high efficiency and quiet.

A few reasons to choose a fan array system 

If you are considering a retrofit, a fan array system can bring you a range of significant benefits. They are:

  •   Easy to install because all parts are small enough to be carried by contractors through your existing doorways. You will not need to factor into your installation costs either building alterations such as doorway widening, or the hire of expensive equipment such as cranes.
  •   Easy to service because they comfortably provide enough space for ongoing maintenance and repairs. You can replace individual fans with ease, without the need for heavy equipment.
  •   Built with redundancy in mind. Even if any of the fans fail, a well-designed fan array system will continue to deliver the required performance.
  •   Quiet, as smaller fans deliver lower radiated and airborne noise levels than large belt-driven fans. Two of the main reasons for the lower sound output are that fan array systems remove vibrations from both rotor imbalances and airway tunnel turbulence. The smaller direct drive fans used by Swiss Rotors produce higher frequency sounds, which are much easier to attenuate.

Fan Array Video

Principles for designing a fan array system

Fan array systems are built using small-diameter fans mounted on a single wall.  Swiss Rotors constructs its fans using seven backward-curved blades, with fans available in 7.5”, 8.86”, 9.84” and 12.4” measurements. A high-performance EC motor powers each fan, offering variable control and complying with UL and AMCA guidelines. In a fan array system, making sure there is appropriate space between each fan can help to deliver optimal performance. A relatively simple calculation reveals whether the spacing is correct.

L / (N x D) ≥ 1.55

In this calculation, L refers to the length of the array, N is the number of fans along that length, and D is the outside diameter of the fan. As long as this calculation remains greater than or equal to 1.55, there is no need for partitions in the fan array system. Fan array systems should provide as much versatility as possible. Swiss Rotors’ new solution offers 100% speed control via 0~10VDC, airflow rates of up to 1,530CFM per single fan, and can operate safely anywhere between -22˚F and 140˚F. Our fan array system is available in product ranges for every application.

Read more about Swiss Rotors’ fan array system here.