A factor strongly influencing the increased rating of equipment was that , previously , the Twin Towers were supplied with chilled water from the Sandton City central plant in the basement . The only practical position for the Atrium on 5th air conditioning equipment was found to be on the roof slab . Therefore , the transformers in the basement substations were increased in rating from 1,250 kVA to 1,600kVA each to cater for what is now a ‘ local ’ load within the building .
At the same time , the existing rising busbars in each tower had to be changed from a rating of 1,800 Amps to 2,500 Amps per phase to cater for the new roof load .
The original Twin Towers generator has been changed to a 1 x 1,000kVA diesel generator which operates independently of the Sandton City generator farm , installed to provide 100 % standby for ESKOM .
All Distribution Boards , especially those originally installed in the Twin Towers , have been replaced with new LV panels containing modern switchgear and mounting facilities , including meters .
As with capital equipment , cables from the original 1973 installation have been replaced with new PVC SWA PVC ECC copper cable . These are 4 core cables with an integral earth conductor embedded in the armouring . All original feeders to major panels not equipped with new ECC cables have been brought into the Sandton City Centre earth cable monitoring system which , using alarms and sms call-out , attempts to protect the older earth cables from copper theft .
Electrical Design Parameters The principle design requirement was to reduce energy and supply demand to levels set by the ESKOM savings regime which falls within their 5 year plan , enhancing the requirements of SANS 204-1:2006 ( at the time ) and reducing the demands on ESKOM ’ s long term strategy .
Control of lighting and other loads by means of sensors , time-clocks , BMS inputs and other electronic means are used to achieve the targets set by both ESKOM and the Green Building Council requirements .
In designing for a Green Building rating , the energy requirements have been reduced to levels appropriate to Green Building Council parameters .
Operational Requirements By providing a reliable , secure power supply , the building is a marketable property able to command high rentals and attract upmarket tenants . This reliability and security comes about because the power supply to the building is covered by the Sandton City Centre ’ s generator farm . This system ensures power to the entire Centre when ESKOM is off-line ( as in loadshedding ).
Furthermore , it is supplemented by the 1,000kVA building generator which stands-in for any commonmode failure of the Farm or when local breakdown leaves an area without power .
Metering and Sub-metering Strategies A smart metering system has been introduced to the Sandton City electrical infrastructure which monitors , reports , bills and alarms against parameters set up in the system based on a methodology defined by the Sandton City Centre Management .
In covering the building with meters , the areas are broken down into zones which correspond with the subdivisions expected according to tenant ’ s layouts , common areas , circulation , ablutions , etc . and which fall in line with the requirements of the Green Building Council .
CONCLUSION Atrium on 5th now has a clear sense of space , its own identity and its own street address with access from Sandton City . It also has longevity in the highly competitive office space environment of Sandton . “ Ultimately , our clients ’ success is of paramount importance to us . The tenant uptake has been encouraging and this bears testimony to the success of the project in that the owners ’ vision for Atrium on 5th has been achieved ,” concludes Pat Henry .
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