Architect and Builder Magazine South Africa March/April 2015 | Page 55

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 the Green Building Council parameters.

Atrium on 5th

Operational Requirements
By providing a reliable, secure power supply, the
building is a marketable property able to command high
rentals and attract up-market 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 load-shedding).
Furthermore, it is supplemented by the 1,000kVA
building generator which stands-in for any commonmode failure of the Farm or when local breakdown, such
as a cable or transformer 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
sub-divisions 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 has generated a lot of interest in the
Sandton community, as evidenced by the large number
of visitors who enter the lobby purely to view and
photograph the building. The building has also become
a very attractive visual focus at the end of the vista along
Maude Street.
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 env