A New Era for Data Center Refrigerants

Introduction: the regulatory drive towards sustainability

The European HVAC industry is undergoing a major transformation following the publication of the new F-Gas Regulation (573/2024). This legislative framework accelerates the phase-down of hydrofluorocarbons (HFCs), with the aim of achieving a complete phase-out by 2050. For manufacturers of cooling and refrigeration products, as well as for end users, this means moving towards refrigerants with a significantly lower Global Warming Potential (GWP).

In this context, A2L refrigerants, which are mildly flammable, have emerged as the leading solution. They offer an effective balance of thermodynamic efficiency, low GWP, and safety. However, the transition to A2Ls requires a comprehensive approach to safety, both in product design and in on-site installation.

The global context: EU F-Gas vs. the Kigali Amendment

While the global community is following the Kigali Amendment to the Montreal Protocol, the European Union has taken a far more ambitious route, introducing stricter quotas and earlier bans. This gap between international and European requirements places EU manufacturers at the forefront of innovation, but it also means operating within a more demanding technical and regulatory landscape.

The prohibitions set out in Annex IV of the F-Gas Regulation are summarized in the following table:

Products	Containing	Effective Date
Chillers with nominal capacity ≤ 12 kW	F-Gas with GWP < 150	01/01/2027
Chillers with nominal capacity ≤ 12 kW	No F-Gas	01/01/2032
Chillers with nominal capacity > 12 kW	F-Gas with GWP < 750	01/01/2027
Monoblock air conditioners with nominal capacity ≤ 12 kW	F-Gas with GWP < 150	01/01/2027
Monoblock air conditioners with nominal capacity ≤ 12 kW	No F-Gas	01/01/2032
Monoblock air conditioners with nominal capacity > 12 kW and ≤ 50 kW	F-Gas with GWP < 150	01/01/2027
Monoblock air conditioners with nominal capacity > 50 kW	F-Gas with GWP < 150	01/01/2030

REACH and PFAS uncertainty: a parallel challenge

The transition to A2L refrigerants, often based on HFOs such as R1234ze, R454B, R32 and R454C, is currently complicated by the REACH proposal concerning PFAS ("forever chemicals"). Some HFOs and their breakdown products are now being closely examined under this broad definition.

This creates a period of regulatory uncertainty: while the F-Gas Regulation is pushing the industry towards HFO-based A2Ls to meet GWP targets, the REACH framework could potentially restrict their long-term use. European Chemical Agency’s (ECHA) scientific committees which relies primarily on the Committee for Risk Assessment (RAC) and the Committee for Socio-Economic Analysis (SEAC) have submitted their assessments and draft recommendations. ECHA supports a comprehensive restriction but, at the same time, recommends targeted exemptions where alternatives are lacking. The reports will be forwarded to the European Commission. Based on these, the Commission will draft specific legislation, which will be coordinated with the EU member states. A final, legally binding EU-wide decision is expected in the coming years. We expect that our solutions for mission critical applications will be handled as “Ban with Temporary Exceptions” which will secure the using of this equipment within its normal product-lifecycle.

As a forward-looking manufacturer, we closely monitor these developments to ensure that our product roadmaps remain robust and adaptable to future restrictions.

Engineering safety: the product level

Designing a unit that uses an A2L refrigerant is not simply a matter of replacing the refrigerant and selecting compatible components: designs based on non-flammable refrigerants are no longer suitable and must be adapted. As a manufacturer, our priority is to mitigate the risks associated with the mild flammability of A2L refrigerants through robust engineering solutions. A cooling unit with lower residual risk simplifies the site risk assessment and reduces the complex responsibilities typically placed on the end user for explosion prevention and safety management.

Our current design incorporates several layers of protection to achieve an intrinsically safe unit. Our A2L systems comply with the requirements of EN 378-1-3, as currently in force. The systems are designed, manufactured, and tested in accordance with these standards so that they are considered permanently technically leak-tight within the meaning of the standard. They meet the requirements for:

the design of the refrigeration components
the selection of suitable materials and joining techniques
the manufacturing and testing processes to ensure leak-tightness until delivery of the equipment

Proof of compliance with the standards – and thus of permanent technical leak-tightness – is provided by our Declaration of Conformity.

Monoblock air conditioners:

Prevention of leaks: hermetically sealed refrigeration circuit with a minimal number of primarily non-detachable connections. Use of caps on valves and service connections, as well as vibration dampers on the hot gas lines.
Prevention of contact with ignition sources: the electrical panel is sealed to keep leaked refrigerant away from electrical parts. Optional heaters operate at a maximum temperature of 100K below the ignition point of the refrigerant.
Detection and alarm system: if a leak occurs and the refrigerant concentration reaches 10% of the lower flammability limit (LFL), the evaporator fan speeds up to expel the refrigerant from the air conditioner, while all other electrical devices are shut down. At 20% of the LFL, the unit is disconnected from the site mains. To ensure continuous operation, the detector must be connected to a separate 230V AC emergency power supply line.
Ventilation of areas where refrigerant might accumulate: all joints in the refrigerant circuit are placed in an area which is actively ventilated by the fan when a leak is detected.
Optimized refrigerant charge in terms of performance and safety. Where necessary, We provide information of minimum room volume matching with the installed safety concept.

Outdoor Chillers:

Redundant ventilation system: compressors in low-noise units are installed within insulated and ventilated compartments. Pre-assembled redundant fans operate continuously for safety, ensuring that if a refrigerant leak occurs, the concentration is diluted and the formation of an explosive atmosphere is prevented.
Advanced detection system: for low-temperature units (down to -40°C OAT), a refrigerant detector is installed at ground level within the compressor compartment. This detector triggers the shutdown of the unit at 25% of the lower flammability limit (LFL), except for the safety-line components.
Independent power supply for safety components: to guarantee continuous operation of safety systems even during a main power failure, a separate 230V AC emergency line and an internal UPS are mandatory for certain versions, ensuring that safety components such as detectors and ventilation fans remain operational.

Ensuring safety at the installation site

Safety does not end at the factory gate. Operators and Designers should consider additional on-site personal safety measures in accordance with EN 378 which defines the applicable requirements based on the refrigerant charge and occupancy category:

Room size: the refrigerant charge per circuit must not exceed the maximum amount specified by EN 378 in according with room classification and occupancy category. We can provide the exact values for your project on request.
Ventilation and placement: ideally, chillers using A2L refrigerants should be installed outdoors. If indoor installation is necessary, the plant room must feature dedicated ventilation systems and leak detection linked to the building management system (BMS).
Safety zones: it is crucial to define safety zones around chillers and air conditioners where ignition sources (such as open flames or non-ATEX electrical equipment) are not permitted.
Discharge routing: safety valves must be piped to discharge into safe, open-air locations to prevent any accumulation of refrigerant in the event of an overpressure release.

Despite all protective measures, the installer or operator must perform a leak test in accordance with Section 6.3.4 of EN 378-2 before commissioning the entire refrigeration system. The operator is responsible for verifying system tightness during operation.

Conclusion

The transition to A2L refrigerants under F-Gas Regulation 573/2024 is a necessary step on the path to carbon neutrality. Although the regulatory landscape, including the PFAS debate, is still evolving, the technologies required to manage A2Ls safely are already mature. Through rigorous product engineering and compliance with strict installation guidelines, STULZ delivers high-performance cooling solutions that combine operational safety and environmental responsibility, resulting in long-term customer value.