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THE DEPARTMENT OF EDUCATION IN JOHANNESBURG MODERNISES WITH SAMSUNG DVM When the old chiller system in the Department of Education building in Braamfontein, Johannesburg, started showing its age, a brand-new energyefficient system was specified. Samsung DVM S units with heat recovery were selected to solve this problem. The building itself was also older, so it was important that the new system installation could use existing ceiling space and existing piping shafts. A total of 20 outdoor DVM S units of 504kW capacity were installed on the roof of the building, supplying 577
kW of indoor capacity via 83 Samsung 4-way Cassettes totalling 114% average combination ratio. This will also allow flexibility for future tenants if the Department relocates in future. Not only is the DVM S system economically viable, it doesn’t ruin the exterior appearance of the building. The project started in March and was completed in September 2016. The problem with the older chiller system was that due to the site having only used one main chiller, it meant that when
the chiller was down and not functioning, the whole building would be without cool ventilation. The current VRF DVM S system has individual floor control, meaning at worst if one outdoor unit shuts down unexpectedly, only one floor would be affected. The HVAC system would carry on as usual throughout the rest of the building. The DVM system used is also a heat recovery system, and is zoned in such a way as to maximise
the benefits of the north/ south heat exchange. The heat recovery system supports more agile operation through simultaneous, continuous operation in both cooling and heating modes. www.fourwaysaircon.co.za
TAILOR-MADE AIR CONDITIONING
Anyone who passes by the new luxury multi-use development known as The Capital Mirage on the corner of Strand and Hudson Streets in De Waterkant (Cape Town) is struck by the structure’s ultramodern facades and high-end finishes. Less obvious but equally impressive, are the building’s state-of-the-art internal mechanical and electrical services. The building is expected to achieve 4 Star Green Star rating by the Green Building Council of South Africa, in large part due to the design team’s focus on environmental sustainability and energy efficiency.
As part of this drive for operating efficiency, the client required that the service costs for each apartment, hotel room and retail tenant be individually monitored, controlled and billed. Providing for tenantspecific electricity metering was relatively straightforward. Tailor-made air conditioning, however, was a more challenging exercise. Sutherland Engineers decided on a Variable Refrigerant Flow (VRF) process because of its ability to provide detailed information and individual control over end-units. The design team appointed Mitsubishi as its preferred supplier. Advantages of their system include its ability to continue operating while individual units are switched off (for example when certain apartments are unoccupied) and the usage information it provides for every unit. Another stand-out feature is the way it uses waste heat from the air-conditioning process to produce domestic hot water for the hotel rooms and apartments.
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The hotel rooms are installed with hideaway units with hard-wired controllers, while the apartments have mid-wall units with remote controllers. This makes it possible to select a different heating or cooling cycle for every room in the building. Although the process of generating hot water from the waste heat of airconditioning systems is not new, the Mirage installation is one of the first to use VRF as its prime source of energy. While the air-conditioning system is in operation, the waste heat is recovered and used to produce domestic hot water via four plant rooms located at different levels throughout the building. The use of VRF air conditioning, coupled with the use of the waste heat and inverter heat pumps for the production of the domestic hot water, results in significant savings in operating costs for both the hotel operator and apartment owners. This is especially so because the condensing units can provide the correct amount of energy/refrigerant required, even as occupancy levels vary. www.msaircon.co.za