36
Project
CHALLENGES PRESENTED The decision to change the HVAC design came with its own set of challenges . These included power supply limitations , tenant considerations , plantroom space restrictions , chilled water pipe routes , change-over co-ordination , logistical planning , noise considerations and last , but no means least , no disruption to the air-conditioning of the building for the duration of the project . The engineers were under no illusion as to the difficulty of the task at hand .
EQUIPMENT SELECTION Chillers The ( 4 OFF ) 10m x 10m high level plantrooms available ( to locate the chillers ) necessitated the use of modular-type chillers . This need was further dictated by the fact that the old cooling towers required to be retained in this space to always enable ongoing air conditioning to the building .
The search was on for chillers of suitable modular capacity and dimensions best suited for the purpose . These were sourced from Hitachi Spain following a visit to a similar ( albeit new ) project in Camden , London , UK ( 28 OFF ) 160kWr ( nominal capacity ) modular chillers were selected and duly ordered on 16 March 2017 .
RPM Consulting Engineers
Air handling units The removal of the existing water-cooled DX packaged units from their individual plantrooms proved a straightforward but timeconsuming exercise . Valve off , disconnect , cut up and remove from site .
Installing new chilled water air handling units into each existing plantroom proved a completely different prospect .
Access to the vast majority of plantrooms was by way of a 600 x 600 opening . This opening could not be enlarged due to the construction of the building ( 350mm thickness cast concrete walls ). To overcome this obstacle , the air handling units were manufactured in various sections , suitably dimensioned to be accessed through the available openings .
Designed by RPM and manufactured locally , these air handling unit sections , including frames , panels , EC plug fans , chilled water coils , were suitably constructed for assembly within the plantroom . Manufactured from aluminium and stainless steel in only three physical sizes , uniformity and longevity is assured .
Controls The control of the new plant consisted of the upgrade to the existing BMS to include additional functions . These new control functions are typically included for additional BMS controllers , sensors , LCD display units , pressure switches , over-heat thermostats , CO2 sensors , actuators , CHW control valves , CHW energy meters , power meters , master control panels and variable speed drives .
Electrical The electrical power supply was extended to the new chiller plantroom areas ( 4 OFF ) at high level . This included for cable , control panels , control wiring , power meters with CT ’ s , new DB board chassis , temporary cooling tower connections , chiller and pump wiring , new chiller panels , cable termination , stripping out old wiring , testing , and commissioning .
Following a successful tender process , the project commenced on 27 September 2017 with the site kick-off meeting .
A plan was duly formulated to always ensure ongoing plant operation ( as required by the tenants ) and to keep subsequent disruptions to an absolute minimum ( weekends , after hours ).
Existing cooling towers making way for aircooled chillers at roof level .
“ After some 24 years of operation and several successful attempts at extending the life of the equipment , the air-conditioning plant was eventually deemed no longer economically viable to retain .”
36
RACA Journal I August 2023 www . refrigerationandaircon . co . za