Chiller retrofit proves benefits of EC fans

AUSTRALIA: Retrofitting EC fans to an air-cooled R134a screw chiller is said to have reduced fan power consumption by approximately 252,000kW over a 12-month period.

Nine EBM Papst EC fans were installed on one of two side-by-side York YCIV air-cooled screw chillers at Roma Mitchell Secondary College in Adelaide. They were controlled using Johnson Controls’ Metasys building management system. This allowed Johnson Controls to compare the performance, energy efficiency and noise levels of the two chillers..

It was found that the chiller with EC fans would achieve energy savings of approximately 252,000kW over a 12-month period – a 49.7% reduction in fan power consumption compared to its twin.

Super school

Located 11km from Adelaide’s Central Business District, Roma Mitchell Secondary College was established in 2011 as one of the South Australian Government’s ‘super schools’, an amalgamation of four schools that resulted in it becoming one of the largest in the region.

Johnson Controls was already contracted to manage the onsite York chillers for the school through Melbourne-based facilities management company Spotless. The EC fan retrofit upgrade was seen as an ideal opportunity to demonstrate energy efficiency proof of concept by upgrading one of the chillers with the new fans. As a test project, the upgrade would allow Johnson Controls to compare the results and, if successful, set a new industry benchmark for increased energy efficiency and noise reduction levels.

Johnson Controls designed the control strategy to ensure the retrofitted chiller remained operating at a constant peak performance range. To ensure this was achieved, a second sensor was installed adjacent to the existing sensor that feeds the PID loop and controls the speed of the condenser fans, supplementing the system if required.

Johnson Controls collected and analysed baseline data prior to and after the EC fan upgrade. In addition to the substantial performance improvements, it was found the chiller operated better under extreme heat weather conditions at/or close to full load conditions. This is important given Adelaide’s harsh temperatures, which can reach up to 46ºC during summer.

Logistically, timing proved to be a challenge for the four-month project as the Johnson Controls team needed to work around the school’s requirements, including class times and change-over periods during semesters. However, the project was completed on time and on budget with a predicted return on investment expected within 20 months.

Ben Sergi, HVAC&R technician at Spotless Group confirmed that the fans appeared to have operated without issues through the warmer period: “There were no high motor temperature cut-outs and the compressors did not appear to go into limiting mode. Regarding capacity, the chiller that had the EC fan motors installed seemed to deal with the high ambient temperatures better than it used to,” he said.