- Published on 01 February 2017
An resent article in RACA on the NGEBS City Mall's HVAC Installation of which Curvent International was proud to be a part of.
Highcrest Engineering in Johannesburg was awarded the contract to handle the HVAC design and Curvent installed the smoke ventilation systems:
BT Ngebs City in Mthatha opened in 2015, boasting the largest ever retail offering for the former Transkei with 6.9MW of cooling on the HVAC side.
BT Ngebs City, the new regional shopping mall in the Eastern Cape province town of Mthatha, officially commenced trading in June last year. The 60 000m2 GLA mall boasts over 150 tenants, a number of which are retail firsts for the former homeland, signalling growing investor confidence in the region.
A comprehensive mix of tenants, including retail, fashion, banking, homeware, health, sports and entertainment, will ensure this development caters to all 478 000 households in the catchment area.
BT Ngebs City forms part of developer Billion Group’s R16-billion investment earmarked for the Eastern Cape region over the next decade. During its construction phase, the R1.4-billion development created approximately 4 500 jobs. An additional 2 500 permanent positions have become available upon completion of the development.
This is but the beginning as the Billion Group is spending over R60-million on roads, bulk electricity, water, sewer, wetland systems and other infrastructure that will benefit the Mthatha community.
The project started in 2012, but groundwork could only start in August the following year as a stream flowing through the site first had to be diverted.
Client brief
Highcrest Engineering in Johannesburg was awarded the contract to handle the HVAC installation on this project, as well as the fire services, including smoke ventilation, fire detection, sprinkler protection and hand-held fire equipment, and fire signage and evacuation.
The brief was for an energy efficient, cost-effective HVAC system that could be easily maintained in the remote Eastern Cape location.
Subsequently, the Highcrest team did various energy simulations and ran through multiple costing options with the client before approving roof top package units and direct expansion ducted hideaway units.
“They opted for this option because the cost premium of having to install a chilled water system in a remote location such as Mthatha would not have been viable,” explains Ayanda Boltina, managing director of Highcrest Engineering. “We had to look at maintainability and capital expenditure versus energy efficiency and life span.”
On the fire side, the team was tasked with providing a cost-effective design, optimising on design allowances while still meeting with regulatory requirements and, of course, maintaining safety.
System description
The HVAC system for all the line shops and all the majors consisted of a combination of 50 Ecoaire ducted hideaway units and HPI rooftop packaged units (14 in total).
Most of the line shops were designed with a shared air conditioning solution as this is more efficient, reducing the cost per square metre. Because these shops generally have the same occupancy and requirements, this was easily done. This system was successfully tested and commissioned using averaging sensors that modulate the AC to give more or less cooling. All the lease documents also specify the temperature requirement as 23°C, +/- 1.5°C.
However, with the restaurants, each client has its own HVAC system. There are no shared systems for the restaurants as the environments differ more drastically and you don’t want to be dumping a fish and chips smell into KFC, for example.
The mall areas aren’t actively air conditioned, but instead are supplied with fresh air at a rate in accordance with the National Building Regulations, SANS 10400. This helped the team to calculate the rates for the shops based on occupancy. However, as there was no such standard for malls specifically, the team looked at international standards like ASHRAE and worldwide best practice standards for the rest of the project.
Heat recovery ventilators were specified for these increased ventilation rates which simultaneously extracts the inside air while introducing fresh air into the mall area; the two air streams interchanging energies to improve system efficiency. So if it’s nice and cool inside but it’s hot outside, the hot air coming in will get cooled by the cool air going out and you will end up having cooler fresh air coming in.
This has resulted in a far more ‘breezy’ mall that is more breathable.
The supply air is pushed through jet diffusers that are mounted in the bulkheads of the mall.
There is spill-over AC coming into the mall from all of the shops so it is constantly positively pressurised. The air goes out of the shops, down the passages and out the main doors.
There are plant rooms located on the roof and under the slab — all which are now operating successfully.
A Mitsubishi variable refrigerant flow (VRF) system with heat recovery was installed in the gym because of its high energy consumption and hot water requirements. A Mitsubishi heat pump was used for heating the pool.
Fire system
As mentioned, Highcrest Engi neering handled both the mechanical and the fire aspect of the contract.
The fire system acts as an early warning system as it is tied to the HVAC system where the fresh air being brought in has to shut down in a fire scenario. As soon as the alarm is activated, not only does the HVAC system shut down, but the smoke ventilation system switches on immediately. Lifts and escalators are turned off, as are all fire dampers between the fire zones.
The team used two-hour fire-rated fans with fire-rated cabling.
A hybrid system that uses both mechanical extraction and natural ventilation was designed.
Challenges
As the site is 1 000km away, it was difficult to manage from Johannesburg. So a good relationship with the main contractor as well as with the sub-contractor was vital.
When it came to the challenges on site, Boltina explains that the HVAC side of things flowed quite well. “Airwaves is a brilliant contractor,” he says. “They always kept us up to date and ordered equipment timeously. They had the right management staff on site.”
However, they weren’t so lucky with the sprinkler contractor and fire detection contractor. “They were short-staffed on site and I had to go live in Mthatha to look after some of our packages,” remembers Boltina.
Another issue was late tenant information. But as Highcrest is familiar with this kind of project, a lot of the delays were circumvented by installing the ducting 3.5m above the floor — leaving the client enough room to put in their own ceilings without any problems. With 200mm allocated for the fire services and 200mm for electrical, this left more than enough room for the ceiling (between 2.7m and 3.1m, with 3m being the norm).
Creating jobs for the local community was very important to the team and requirements for local labour usage and skills transfer on site were built into the spec. However, this proved a bit of a challenge as the skills needed during the construction phase of the project were not readily available in Mthatha and the surrounding areas. Also, taking the sheer scale of the project and its commercial nature into account it was very important that the mall open on time and that the work was of acceptable quality.
List of professionals
Owner / Developer: Billion Group Architect / Designer: LYT Architecture Project manager: SIP Project Managers
Consulting engineer
Electrical - CKR Mechanical - Highcrest Engineering Wet services - Ingplan Civil - WSP
Contractors
Main building - GD Irons Construction HVAC&R - Airwaves Electrical - ADL Electrical
Product suppliers
Roof top packaged units - HPI Ducted hideaways - Ecoaire VRF (gym) - Mitsubishi Heat pump - Mitsubishi Diffusers- Rickard Smoke ventilation AMS Roof ventilators - Curvent International PTY Ltd Ducting - Airwaves
