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When a major retail space at Lakeside Shopping Centre was due for a new tenant fit-out, the brief was clear: create a comfortable, efficient indoor climate with long-term performance in mind. But the path to achieving this was anything but straightforward.
At first glance, the solution appeared simple - install air handling units equipped with direct expansion coils and connect them to external condensers using R32 refrigerant. This setup would provide heating and cooling through an all-air system, and R32’s relatively low global warming potential made it a reasonable starting point.
But when the design team dug deeper, cracks began to show. Each AHU would require five separate condensers to stay within refrigerant safety limits. That meant 20 separate units for the main store floor alone, raising significant concerns over system complexity, controllability and compliance with EN378 safety standards. Moreover, the total refrigerant charge would equate to a carbon footprint of 13.5 tonnes of CO₂.
A pivot toward simplicity and sustainability
In collaboration with the project stakeholders, Swegon proposed a more considered approach: retain the overall function of the AHUs but replace refrigerant circuits with water-based combi-coils connected to air source heat pumps. These ASHPs used R290 - a natural refrigerant with a near-zero GWP.
This change did more than reduce environmental impact. It also addressed the underlying system design challenges:
- Controllability improved with a hydronic setup, favouring part-load operation.
- Complexity dropped dramatically: one set of water pipes, one data cable and one ASHP per AHU.
- Safety risks were significantly reduced, as the refrigerant charge was now confined to a factory-sealed unit, less than 10 kg of R290 per system, with a total CO₂ equivalent of just 0.2 kg.
In essence, the revised design delivered a clearer, cleaner and safer indoor climate solution, with less engineering burden and a smaller environmental footprint.
Smarter optimisation, smaller plant
But the team didn’t stop there. Using Swegon’s sorption rotors inside each AHU, the system was able to recover more latent energy, cutting the cooling load on the coil by 17%. With AHUs and ASHPs paired 1:1, flow and return temperatures were fine-tuned to suit the system’s real-world demands. This fluid temperature optimisation allowed for smaller, more efficient ASHPs to be selected without compromising on comfort.
Swegon’s SmartLink controls ensured that this adaptive operation wasn’t just possible, it was automatic. These intelligent controls continuously optimise the interaction between AHUs and ASHPs, adjusting temperatures to balance performance and efficiency over the system’s lifecycle.
A single combi-coil: fewer parts, smarter performance
An important feature of the Lakeside system is the use of a water-based combi-coil - a single coil capable of handling both heating and cooling duties depending on the temperature of the water supplied.
This approach stands apart from the more conventional setup which typically involves two separate coils, one for chilled water and one for hot water. By combining both functions into a single coil, Swegon’s design simplifies the system architecture in several meaningful ways:
- Reduced airflow resistance: A single coil means less pressure drop compared to having air pass through two coils in series. This allows the fan to operate more efficiently, lowering energy use and potentially extending fan lifespan.
- Simplified controls and pipework: Only one set of valves and actuators is required to modulate water flow through the combi-coil, making the system easier to commission and maintain.
- More compact and flexible: With fewer physical components, the AHU design can be more space-efficient - an important consideration in retrofit or constrained plantroom applications.
The combi-coil setup also supports quicker response times during mode shifts, such as in shoulder months when external conditions may drive frequent transitions between heating and cooling. Thanks to the SmartLink coordination between the AHU and the heat pump, system lag is minimised and comfort is maintained more reliably.
Delivery backed by expertise
Execution matters as much as design. That’s why Swegon’s dedicated project engineer led the delivery in close partnership with the contractor and service teams. From managing complex, out-of-hours deliveries to on-site assembly and commissioning, the project benefited from hands-on support throughout.
This collaborative delivery ensured the system was up and running as intended, providing not just indoor comfort, but peace of mind.
