Pretoria CBD retailer gives 50-year-old HVAC system a refurb

Metro Home Centre main entrance.

By Eamonn Ryan & Dusan Stefanov Pr Eng Mech | All images © RACA Journal | Eamonn Ryan

Metro Home Centre in Pretoria CBD occupies an older building with an HVAC system dating back to the mid-1970s that was in a need of refurbishment. When bidding for the project ODA Design used state-of-the-art 3D coordination software and consequently they were appointed as the mechanical consultants for various building services.

This building, located in Pretoria CBD, was originally developed for use as a Pick ‘n Pay store. The property was subsequently bought by the current owners and turned into non-perishable goods retail store Metro Home Centre. The building itself was refurbished with a fresh open-plan appearance, thus requiring new HVAC and other mechanical systems to meet the same standards.

Mechanical engineer and owner of ODA Design, Dusan Stefanov, adds: “They had inherited an HVAC system that was installed back in the early 1970s, and the building had no fire protection or smoke ventilation at any level.”

Because of the 2019 Covid-19 pandemic, the project has had a rather longer than expected duration. It commenced in October 2018 but was interrupted by Covid-19 and only later resumed for a successful completion in mid-2022. The delays were not just due to the public gathering and health restrictions, explains Stefanov, but the economic factors which hit the entire construction industry. It meant that two of the original contractors went out of business during this prolonged period, with a subsequent need to re-tender parts of the reminding systems and appoint new contractors.

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The building refurbishment was also a measured process requiring considerable deliberation to meet the owners’ specifications. “As this was a refurbishment project, the client requested provision for as much retail space as possible. After owners’ consultations with architects and interior decorators, they opted for a fully open plan shop layout of 7.200m2 retail space.”

The building today looks extremely m0dern, with customers on its Facebook page commenting positively on its appearance and describing it as customer-friendly. The retail personnel also add that the air-conditioning is extremely comfortable.

The HVAC system and installation

Stefanov describes the HVAC system as consisting of four independent installations:

• Two air-cooled Carrier chillers and four air handling units, together with spiral ducting and constant volume swirl diffusers, serve ground floor retail area
• Samsung DX inverter units were installed for mezzanine level offices and restaurant area
• Rooftop ducted unit was installed in the newly built annex and serves two additional retail levels
• Toshiba VRF heat recovery system serves main offices, situated at the top of annex building

“Fire detection and sprinklers have been installed throughout the building. The VRF heat recovery system was implemented in the new offices and a heat pump rooftop unit was selected for the new retail levels as an energy efficient solution,” he adds.

There were several design challenges in meeting the specifications and installation, says Stefanov: “Firstly, performing heat load calculations was a mammoth task, as all the old and newly built areas are fully integrated – but have completely different purposes.

“Secondly, the fresh air and extract air volumes had to be calculated and commissioned precisely in order to avoid kitchen and restaurant scents spilling over into the retail area and offices.

“Thirdly, a sprinkler design also proved to be challenging to a degree, due to the diversity of various areas’ allocation and space limitations. In the end, because of space limitations the pump room for the sprinklers had to be erected outside the main building, as well as the fire water storage tanks.”

Cooling/heating capacity

The builders work was performed by a building company NJ Construction. The design and selection of equipment also required working around the fact that there was pre-existing equipment. For instance, three of the AHUs were refurbished with a fourth purchased new. Choice of other equipment was dependent on a number of factors, explains Stefanov: space constraints inside the building; ability to do the required function; and finally the price.

“Each product went out to tender, and I would select and recommend them to the owners, who had the ultimate say.

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What eased the project management process for ODA Design was its expertise in using Revit – a 3D coordination software for mechanical, electrical and plumbing (MEP) services. Stefanov says that company’s investment in an intensive upskilling on Revit, combined with an involvement in the local building industry spanning 25 years, has proven tremendously beneficial to customising building information modelling (BIM) to suit the local contracting environment.

Within the mechanical aspect of MEP, it covers the following building services: HVAC; fire protection, sprinkler and FHR systems; and compressed air.

Stefanov describes Revit in the following terms: It is an intelligent 3D model-based design set of tools that supports a modelling workflow, whereby deliverables such as drawings and schedules come directly from a single, unified model. Changes are automatically reflected in all views and bill of quantities schedules of the model, with adjacent or connected elements automatically updated to maintain established relationships.

Project manager, HVAC mechanical engineer and owner of ODA Design, Dusan Stefanov.

“We decided to incorporate Revit into our BIM offering as more and more architects are using Revit to generate building models. Furthermore, we had noticed that current HVAC Revit models lacked implementation of the full Revit potential and thus we decided to go deeper down that route,” says Stefanov. “I firmly believe that Revit stands for ‘Revise it’ because in our industry, one is constantly revising plans, not just during the design phase but during construction process, as well.

“Therefore, when issuing tenders one doesn’t have to worry about the accuracy of the BoQ, as it cannot be manipulated,” says Stefanov.

ODA Design would like to thank all the participants and the client for their contribution, commitment, patience and perseverance that lead to the successful completion of this demanding project.

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