The EC plug fans replaced the existing AC belt driven backward-curved fans throughout the building to save approximately 50% of energy. Fans account for the consumption of a significant amount of energy in commercial buildings.
The original fan and air handling unit (AHU) arrangement for level 14 at the Wakefield House Building comprised of a coil face bypass arrangement, with air distributed via a belt driven backward curved centrifugal fan arrangement.
In addition to performance issues, the AHU also failed to adequately distribute air to the floor. The system type and the fan’s proximity to the cooling coil reduced the cooling capacity of the AHU as only part of the coil face was being utilised.
Locating the fan so close to the cooling coil created turbulence and increased the system static, which in turn reduced the supply air quantity by approximately 10-15% from design. When combined with the reduced performance of the cooling coil, the net reduction in capacity to the floor was approximately 45% from design.
Starting currents for each day exceeded 80 Amps while the average current across the phases throughout daily fan operation was 8.55 Amps.
The existing fan was replaced by an ebm-papst EC plug fan in October 2011 by System Solutions Engineering Pty Ltd, an engineering firm and consultancy based in Adelaide.
The new EC plug fan was installed away from the cooling coil, and the new damper, rearranged above the cooling coil in the bypass ductwork was installed to provide an equivalent pressure drop to the cooling coil, which ensured more stable distribution and controllability of supply air.
The EC plug fan provided uniform air pressure and volume across the whole cooling coil, achieving greater capacity from the coil. The retrofit enabled a 10% increase in airflow, which combined with the resultant increased coil efficiency, enhanced the cooling delivered to the floor by approximately 15-20%.
Starting currents now approach 6 Amps while the average current across the phases throughout daily operation of the EC plug fan is 4.7 Amps.
The commercial building is now able to achieve annual savings of 9,470.7 kWh and 6.5 tonnes of CO2 emissions.
Up to 70% of total energy consumption in commercial office buildings is attributed to HVAC systems. A reduction of about 50% that can be achieved by replacing existing AC belt driven fans with EC plug fans will have a significant impact on the total energy consumed as well as greenhouse gas emissions.