September 2019

42 n ENERGY EFFICIENCY September 2019 www.drivesncontrols.com Durham college boosts DEC rating by installing 30 HVAC drives N ew College Durham is a higher education and sixth form college in County Durham. For many years, sustainability and carbon reduction have been a key element of its operations. It has previously implemented energy-saving measures including solar power, rainwater harvesting and BMS (building management system) optimisation. In July 2017, the college decided to install variable-speed drives in 30 AHU (air-handling unit) fan applications. The drives were integrated into an existing Cyclon BMS with kWh consumption data being analysed across the site. Before installing the VSDs, all of the College’s AHU fans ran continuously at full speed, wasting a lot of energy. To remedy this, carbon dioxide sensors were installed in the AHU return air ducts and connected via the BMS, allowing the actual occupation level of each area being served to be measured and controlled. The fan speeds were then reduced or increased automatically by the drives to provide the exact rate of air exchange needed to maintain a healthy and comfortable environment. One year on, Richard Newton, the College’s estates manager, reports that“we’ve made very large energy savings thanks to the accurate control the new inverter drives have provided over the air moving systems within the College. Crucially, in order to achieve the maximum benefits, the units are being used in tandem with focussed building reviews and regular optimisation of control systems at a BMS level. The big benefits we’re getting have led us to looking into other applications within the building where there is potential for using inverter drives to move from fixed-speed to variable-speed operation, and we already have several new applications in mind.” The energy savings have been reflected in improvements to the College’s already good Energy Performance Operational Ratings, which are included in its DEC (Display Energy Certificate). The rating for the main building has improved from 60 to 55, while the sports and music building has improved from 57 to 54. The College’s estates and facilities team discovered that the benefits of using VSDs are not limited to energy savings. “They have also reduced the need to change filters and belts within our many AHUs because we pull less air over a given period through the filters – which means they last proportionally longer,” Newton reports. “In addition, the drive belts are less stressed due to the controlled starting and stopping, so they also last longer. This has led in turn to saving physical resources and financial outlay. “We have also noted a marked benefit to the working environment and a significant reduction of complaints during extreme weather,” he adds, “resulting from the capacity to alter speeds and air flow from a supply and extract point of view in relation to air quality, temperature, humidity, and so on. All of these benefits are easily perceived by building users and have been noted in reviews submitted to us in the estates department.” The VSDs that the College is using are Danfoss VLT HVAC FC 102 models supplied by the Hinckley-based HVAC specialist, Digicon Solutions, which also performed an initial survey of the site. The drives incorporate functions developed to enhance the performance of pumps, fans and compressors. n A higher education college in Durham is reaping the benefits of installing 30 dedicated HVAC drives in air-handling fan applications. As well as saving energy, the drives have cut maintenance costs, and reduced complaints from students and staff during periods of extreme weather. New College Durham is reaping the benefits of installing 30 variable-speed drives to control HVAC fans The college has found that its VSDs are delivering several unexpected benefits, besides saving energy