In the medical sector, refrigeration is far more than a convenience, it’s a critical safeguard. Production facilities, warehouses and research laboratories all rely on stable, validated temperature conditions to ensure the integrity of medicines, samples and research materials. Even slight deviations from the set point can have serious consequences.

To protect against risks, installations are often built with 100% redundancy: two fully independent refrigeration systems designed to ensure uninterrupted operation. Yet this very redundancy raises important design questions. Should both systems operate simultaneously? Should one remain in standby, coming into service only when an alarm occurs?

Whatever the configuration, one requirement is essential: temperature stability must always remain within the validated thresholds.

The path from HFCs to natural refrigerants

Historically, medical refrigeration systems were built using HFC (hydrofluorocarbon) refrigerants such as R404A. These synthetic gases offered reliable performance but came with a high global warming potential. As environmental regulations become stricter worldwide, the industry is now rapidly moving towards natural refrigerants, which offer comparable performance with a far lower environmental impact.

The shift to CO₂ systems represents not only a compliance measure but also an opportunity: to rethink the entire refrigeration system design for better energy efficiency, smarter control, and long-term sustainability.

A case from Copenhagen

Pharmacold A/S, a Copenhagen-based refrigeration specialist with decades of experience in the medical sector, was tasked with upgrading a freezer room for a local pharmaceutical company. The original installation, operating on R404A, consisted of two independent condensing units located in a machine room, each with its own control panel.

The design was typical of older-generation systems: a pump-down circuit with thermostatic expansion valves, solenoid valves, and simple on/off temperature control. Ventilation was required to remove heat from the condensers. Efficiency optimisation was minimal, and suction pressure control relied entirely on a low-pressure switch. In short, there was clear potential for improvement.

The project goals were defined as follows:

• replace the HFC system with a natural refrigerant alternative;
• maintain 100% redundancy with two independent units;
• introduce electronic expansion valves for more precise control;
• improve energy efficiency while keeping the temperature within ±3 °C of the requested set point. In practice, the current result is actually ±2.5 °C around the set point.

A new design philosophy

The new installation replaced the legacy HFC setup with two high-efficiency CO₂-based systems. Each unit operates independently yet works in harmony to maintain precise temperature control.

One of the main innovations was the redundancy strategy. Instead of relying on a traditional standby system controlled by remote on/off signals, Pharmacold implemented a dual-active configuration:

• both systems remain active, but one operates at a slightly offset set point (around +2°C);
• the evaporator fans on the standby unit continue running, ensuring uniform air distribution and stable temperatures throughout the room;
• a weekly digital changeover switch alternates the lead and lag units, ensuring balanced operating hours and uniform wear;
• in the event of a changeover fault, both units automatically revert to the same set point, maintaining uninterrupted operation.

This simple yet robust control logic ensures continuous redundancy without the need for complex supervisory systems, offering temperature stability through design simplicity.

Smarter monitoring and validation

For the medical industry, compliance and traceability are as essential as performance. The system was therefore equipped with dual supervision:

• an independent temperature logging system managing high/low alarms and regulatory validation;
• a central monitoring platform providing real-time data on compressor operation, defrost cycles and energy performance.

The monitoring system communicates directly with the customer’s building management system (BMS) over TCP/IP, integrating alarms, operating data, and system status. This dual-layer structure ensures regulatory compliance while also delivering valuable insights for optimisation and validation during both standard operation and defrost cycles.

Measurable results

The upgrade produced immediate, measurable improvements:

• more stable temperature control, both in steady-state and during defrost cycles;
• reduced compressor runtime, thanks to inverter-driven modulation;
• lower energy consumption, leading to a reduction in operating costs;
• reliable redundancy, with seamless changeover between the two systems.

The result is a future-proof, energy-efficient and regulation-compliant refrigeration system tailored to the strict reliability standards of the medical industry.

A blueprint for the future

This case demonstrates how the transition from HFCs to CO₂-based systems can bring tangible benefits in one of the most critical application sectors. Beyond the environmental advantages of natural refrigerants, the combination of modern control logic, data-driven monitoring and intelligent redundancy delivers significant improvements in efficiency and reliability.

For Pharmacold A/S and its customer, the key takeaway was clear: keep it simple. By focusing on smart yet straightforward design principles, it is possible to achieve validated temperature stability, enhanced energy performance, and long-term sustainability, all essential ingredients in the next generation of medical refrigeration.