Government-owned office building in Adelaide more efficient after EC retrofit
Kevin O'Reilly (Director at System Solutions Engineering) planned and rolled out the retrofit.
The iconic Wakefield House Building in Adelaide, South Australia, was suffering from poor fan installation, and as a result, was not delivering airflow as per the National Construction Code (NCC). The below case presents the application of an idea that was firstly trialled on level 14 of the Wakefield House building and was very successful. A two-step retrofit program was undertaken to bring the installation up to date and bring the building to compliance with the NCC.
For commercial office buildings, up to 70% of the total energy use is attributed to the heating, ventilation, and air conditioning (HVAC) systems. Fan energy is typically the most significant consumer of energy within a commercial building. Approximately 50% of energy can be saved by replacing the existing AC belt driven backward-curved fans throughout a building to EC plug fans.
Wakefield House, Adelaide
The original fan and air handling unit (AHU) arrangement for level 14 of the government-owned Wakefield Building in Adelaide, which is typical throughout all floors of the building, comprised a coil face bypass arrangement, with air distributed via a belt driven backward curved centrifugal fan arrangement. In October 2011, one existing AHU fan was replaced by an ebm-papst EC plug fan on level 14 to verify results for a potential future rollout for the rest of the building. Minor works to the damper were also performed.
The retrofit was very successful and this lead to the South Australian Government providing immediate funding to implement the progressive roll out of the remaining 18 floors (19 stories of occupied floors). The retrofit of the whole building has been completed with the retrofit giving the benefits of:
Old System
The main issues with the above arrangement and system relate to performance and the ability to adequately distribute the air to the floor. Due to the system type and the fans proximity to the cooling coil, cooling capacity of the AHU is reduced as only part of the coil face is utilised. Air from the fan is only incident on part of the cooling coil, which then is reflected by insufficient capacity being delivered to the floor.
New System
The new ebm-papst EC Plug fan was installed away from the cooling coil, and the damper was rearranged above the cooling coil in the bypass ductwork. The new damper was installed to provide an equivalent pressure drop to the cooling coil, which provides more stable distribution and controllability of supply air. The EC Plug fan pressurises the plenum chamber and rather than delivering an uneven air profile as per a centrifugal fan it provides uniform air pressure and therefore volume across the whole cooling coil, achieving greater capacity from the coil.
For commercial office buildings, up to 70% of the total energy use is attributed to the heating, ventilation, and air conditioning (HVAC) systems. Fan energy is typically the most significant consumer of energy within a commercial building. Approximately 50% of energy can be saved by replacing the existing AC belt driven backward-curved fans throughout a building to EC plug fans.
Wakefield House, Adelaide
The original fan and air handling unit (AHU) arrangement for level 14 of the government-owned Wakefield Building in Adelaide, which is typical throughout all floors of the building, comprised a coil face bypass arrangement, with air distributed via a belt driven backward curved centrifugal fan arrangement. In October 2011, one existing AHU fan was replaced by an ebm-papst EC plug fan on level 14 to verify results for a potential future rollout for the rest of the building. Minor works to the damper were also performed.
The retrofit was very successful and this lead to the South Australian Government providing immediate funding to implement the progressive roll out of the remaining 18 floors (19 stories of occupied floors). The retrofit of the whole building has been completed with the retrofit giving the benefits of:
- 50% input power reduction
- 20% increase in cooling capacity available
- 10% increase in airflow available
Old System
The main issues with the above arrangement and system relate to performance and the ability to adequately distribute the air to the floor. Due to the system type and the fans proximity to the cooling coil, cooling capacity of the AHU is reduced as only part of the coil face is utilised. Air from the fan is only incident on part of the cooling coil, which then is reflected by insufficient capacity being delivered to the floor.
New System
The new ebm-papst EC Plug fan was installed away from the cooling coil, and the damper was rearranged above the cooling coil in the bypass ductwork. The new damper was installed to provide an equivalent pressure drop to the cooling coil, which provides more stable distribution and controllability of supply air. The EC Plug fan pressurises the plenum chamber and rather than delivering an uneven air profile as per a centrifugal fan it provides uniform air pressure and therefore volume across the whole cooling coil, achieving greater capacity from the coil.
Old Performance
Contributing to the insufficient capacity is the reduction in supply air to deliver cooling to the floor. Locating the fan so close to the cooling coil creates turbulence and increases the system static, which in turn reduces 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 is approximately 45% from design.
New Performance
As part of the upgrade works, airflow was increased by 10% returning the supply air quantity to the design figure and combined with the resultant increased coil efficiency, cooling delivered to the floor was increased by approximately 15-20%.
Summary
Power measurements were taken before and after each upgrade, and the measurements logged for reference. After 2 years in operation, a recent site evaluation has confirmed that power savings for the building are at 194,000kWh per annum, equivalent to 132t CO2-e.
As fan energy is typically the most significant consumer of energy within a commercial building, the reduction of approximately 50% from the replacement of the existing AC belt driven fans throughout the building to EC Plug Fans had a significant impact on the total energy consumed, as well as reduction in green house gas emissions.
