Projects
HVAC SYSTEM
The air conditioning systems consists of a chilled water,
zoned variable volume system. Chilled water is generated
by four air cooled chillers located on the roof. Chilled water
is distributed via a primary/secondary pumping system.
Approximately 17 appropriately zoned air handling
units (AHUs) on the roof distribute air to the various zones
via externally insulated sheet metal ducting. The units are
complete with dry economy cycles. Variable air volume (VAV)
ceiling diffusers supply air to the space to suit the load.
The master diffusers are connected to the Building
Management System (BMS) and room temperature sensors
are integrated within the diffusers. The complete system
(including diffusers) are controlled and monitored by a
server based BMS system. The BMS provides monitoring
features for a number of integrated services within the
building, in addition it provides full heating, ventilation and
air-conditioning (HVAC) control.
Basements are mechanically ventilated. The extract fans
are high temperature fans which also act as smoke extract
fans. CO sensors control the fan VSD’s. In addition, impulse
fans supplement ventilation in the basement.
The following environmentally sustainable strategies
have been included in the 144 Oxford HVAC design:
• High efficiency equipment
• Low pressure ducting and pipe sizing
• CO2 monitoring and control of the fresh air
• CO control of basement ventilation fans
• Full fresh air economy cycles
• Small footprint diffuser zone control
• Zero ozone depleting potential (ODP) refrigerants
and insulants
Designed initially to
incorporate a hotel and office
component, 144 Oxford Road
was later changed to a multi-
tenant office building.
Offices
The air conditioning system consists of the following:
• The central Chilled Water Plant will consist of multiple
air-cooled chillers located on the roof utilising 2-pipe
chilled water reticulation.
• Four chillers will be provided, each with 25% of the
total design capacity of the building.
www.hvacronline.co.za
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Chilled water is distributed via a primary/secondary
pumping system.
Appropriately zoned air handling units on the roof
distribute air to the various zones via externally
insulated sheet metal ducting. The units are complete
with temperature controlled dry economy cycles.
Variable air volume (VAV) ceiling diffusers supply air
to the space to suit the load. Perimeter diffusers have
electric terminal heaters.
The master diffusers are BMS addressable and room
temperature sensors are integrated within the diffusers.
The air handling unit supply temperature is determined
by the diffuser demand.
The complete system (Including diffusers) is controlled
and monitored by a PC based direct digital control
(DDC) BMS system. In addition, electrical and wet
services are monitored by the BMS.
Ventilation
Toilets are mechanically ventilated to meet the building
regulations. Smoke extract is also provided on the office floors,
staircases and fire lifts will be pressurised during a fire scenario.
Control system
• The air conditioning and ventilation system is controlled
by a PC-based DDC system.
• A base-building BMS is provided by the Landlord as an
extension of the HVAC controls installation for the purposes
of base-building energy management and metering.
Air-conditioning and ventilation systems are integrated as
follows:
• Central cooling/heating plant – to allow central
scheduling, after hours operation and system
optimisation.
• Individual AHU’s and VAV zone master controllers – to
allow centralised space temperature, setpoint and
operational monitoring.
• Ventilation and fresh air monitoring scheduling and
optimisation.
GETTING THE JOB DONE
Each floor in the building is almost identical. The project was
completed at the end of 2019. “It was about a 24-month
construction period,” says Huddle. Changing part of the design
due to a major change in the building use was a bit of a ‘setback’
– according to Huddle. “Because we then had to make the best
of the building’s existing structure and vertical risers, however,
working closely with the architects cushioned any delays that
we could’ve experienced.” RACA
RACA Journal I May 2020
53