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For the last 30 years, centrifugal fans have been a central component of air handling units (AHUs). However, with the pressures of the ErP Direcve and energy eciency under increasing scruny, building owners are now upgrading these units to plug in fans for greater eciency and longer AHU life.


PLUG FANS BSEE Plug in for longer life AHUs

centrifugal fans are no longer the most suitable option available. In terms of an AHU, the aspect which has the highest electricity consumption is the fan, and replacing an outmoded centrifugal fan can make serious savings. The issue with centrifugal fans is that energy loss is inherent in their operation. Traditionally driven by a motor in a belt and pulley arrangement, improving the efficiency of these units is extremely difficult. Whilst there are models available that can be operated as direct drive fans to eliminate belt losses, these are restrictive and have limited applications. The only other gain has been from moving from a forward curved to a backward curved design to improve aerodynamic efficiency. Given that there has been little progress made in raising the efficiency of these units, it is no surprise that an alternative solution has emerged to cater for rising HVAC standards. The plug fan is a purpose-designed, free- spinning backward curved centriflow impeller which can be used within the casing of an AHU, providing an effective, energy-saving replacement for centrifugal fans.


A typical upgrade from a double inlet centrifugal fan to an inverter driven direct drive plug fan, at average UK electricity prices and AHU annual

s HVAC has evolved in-line with energy efficiency standards, the original

running hours, will lead to energy savings in the region of 30 per cent per annum and payback periods of less than three years*.

In fact, a government organisation based in Surrey that upgraded the belt driven centrifugal fans in its building’s AHUs (originally installed in the 1970s), to plug fans connected via a variable speed inverter drive, saved £45,493 in the first year alone.

Modern plug fan technology can be used to significantly increase the duty both the volume and pressure) of the air being supplied through HVAC equipment, potentially alleviating the need to install additional AHUs to serve an increased load.

Many building operators and owners that have extended the life of their AHUs by replacing old centrifugal with modern plug fans are using data logging to predict and validate energy savings.

In addition to delivering energy savings, plug fans offer lower noise levels, and are easy to fit and maintain. For many building owners, a quick and simple retrofitting process is crucial in order to minimise downtime for occupiers.

When it comes to commerical buildings, energy is not only a hot topic now, but will continue to be so for years to come. With this in mind, upgrading to ErP compliant plug fans can be a simple way of improving the efficency of an entire building. By integrating

plug fans into existing commercial ventilation systems, consumption can be reduced, along with electricity load and CO2 emissions. Given the ease with which these can be installed, making the move from centrifugal fans to plug fans is a no-brainer for building managers looking to modernize their HVAC systems.

*Energy savings are dependant on the electricity tariff for the site (p/kWh), annual operating run hours and motor size/electricity consumption. uFor more information email, call 01206 222 555 or visit:

uUpgrading to ErP compliant plug fans can improve the energy e ciency of an enre building.



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