Project
WSP was requested by the client to make provision for the possible future addition of split air conditioners in the apartments , depending on the requirements of individual purchasers . This was not a simple task , as this includes the provision of mechanical fresh air supply in accordance with the current SANS 10400 regulations .
CHILLED WATER PLANT The central chilled water generation plant has a total diversified cooling capacity of 1460kWr , with two water cooled Climaveneta screw compressor chillers of equal capacity , each providing some 65 % of the design total building load .
This plant is located in a designated plant room in the lower basement level , immediately adjacent to the electrical LV and generator plant room , which significantly reduced the cost of expensive cables feeding the chiller plant .
The chilled water system is configured as a de-coupled system , with two primary chilled water and two secondary chilled water pumps with variable speed drives . The secondary ( building ) loop is a variable flow system , with all air handling units and fan coil units fitted with two way modulating type control valves .
There are two BAC cooling towers , of the low profile open type , installed on the roof of office A building . Due to the close proximity of these towers to the apartments , the original design specified sound attenuation on both the inlet and discharge of these towers . As a result of subsequent value engineering , and with input from the appointed acoustic consultant , it was decided to omit the discharge sound attenuators . This has since proven to be the correct decision , as the overall ambient noise levels have been found to be well within acceptable limits .
Interestingly , it should be stated that at the initial design stage , a study was conducted jointly between WSP and the electrical consultant to determine the comparative energy consumption costs between open type cooling towers and closed-circuit coolers . This study revealed , that in this case , the annual operating costs for closed circuit coolers were some 47 % higher than those for open cooling towers . This , coupled with the much higher capital cost for closed circuit coolers , decided in favour of the latter for use on this project .
THE HOTEL The hotel comprises of 80 keys of approximately 20m 2 in size over five floors and is fitted out to a four-star standard . On level 2 there is a restaurant / lounge with an open view kitchen and reception area , whilst the staff areas , administration office and BOF / stores are located on level 1 .
Guest rooms are fully air conditioned by two pipe chilled water fan coil units with electric resistance heating . These units are Intramech , and utilise two way modulating chilled water control valves for capacity control . These fan coil units operate on a stand-alone control basis ( not linked to the Building Management System ).
A single fan at roof level supplies filtered fresh air ( unconditioned ) to each guest room as well as to the corridors , lobbies and linen rooms . Extraction from bathrooms is achieved by means of a single axial type extract fan located at roof level , with individual riser ducts , common to two adjacent rooms on each floor . Fresh air fans and extract fans are monitored by the BMS and operate on a 24 / 7 basis .
Chilled water piping to the rooms is reticulated vertically from the basement plant room in a single riser shaft , and horizontally on each floor in the corridor ceiling voids .
Most mechanical and electrical / electronic services reticulation had to share the corridor ceiling voids for horizontal reticulation , which required careful co-ordination and planning between these services within the limited space available . Such co-ordination and clash detection was all carried out in Revit 3D model space , by the various consultants and architect .
WSP
Figure 1 : A 3D rendering of chiller plant room .
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The large bore chilled water and condenser water piping is routed within the upper basement level to a number of riser shafts , from where it is reticulated vertically through the buildings .
RACA Journal I January 2022
WSP
Figure 2 : Co-ordinated 3D model of corridor ceiling .
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