New charge limits for flammable refrigerants: your questions answered
Earlier in 2019, the International Electrotechnical Commission (IEC) revised its safety standard IEC 60335-2-89, and increased the charge limit for flammable refrigerants in self-contained commercial refrigeration appliances.
This is important news, as the move to low global warming potential (GWP) refrigerants will mean commercial refrigeration will make increasing use of flammable refrigerants like propane (R290) and isobutane (R600a).
Choosing between CO₂ transcritical and A2L refrigerant systems for commercial walk-in coolers involves tradeoffs in efficiency, regulatory compliance, system pressure, installation complexity, serviceability, and total cost of ownership.
CO₂, also known as R744, offers a very low-GWP and non-flammable refrigerant pathway, but it operates at significantly higher pressures and requires system components designed for CO₂ operation. In warm climates, transcritical CO₂ systems may require additional technologies such as parallel compression, ejectors, or advanced controls to reach optimal efficiency.
A2L refrigerants such as R454C and R455A are low-GWP options for selected commercial refrigeration applications. They can support a more conventional refrigeration architecture than CO₂, but because A2L refrigerants are mildly flammable, they require careful attention to charge limits, equipment listing, leak detection, ventilation, electrical safety, and local code requirements.
However, the change has the potential to cause confusion. For example, the new charge limits will take effect in different countries at different times, cover some applications but not others, and depend upon the size of a room where the unit can be used. To help, we’ve answered some common questions about the new limits.
CO₂ transcritical vs A2L systems for commercial walk-in coolers
Commercial walk-in coolers and freezers can use different refrigerant strategies depending on system size, location, efficiency target, regulatory requirements, safety classification, service capabilities, and long-term refrigerant strategy. Two important low-GWP pathways are CO₂ transcritical systems and A2L refrigerant systems.
Neither option is universally best for every project. CO₂ is often selected when the project prioritizes a non-flammable refrigerant and very low GWP. A2L refrigerants are often considered when the project needs a lower-GWP solution with a more conventional refrigeration architecture, provided the system is designed for mildly flammable refrigerants and meets applicable safety requirements.
CO₂ transcritical vs A2L: comparison for walk-in cooler applications
| Decision factor | CO₂ transcritical system | A2L refrigerant system |
|---|---|---|
| Refrigerant type | CO₂ / R744 | Mildly flammable A2L refrigerants such as R454C, R455A, or other approved options depending on market and application |
| GWP profile | Very low GWP | Low GWP, typically much lower than legacy HFC refrigerants |
| Safety classification | Non-flammable | Mildly flammable |
| System pressure | Operates at significantly higher pressure than many legacy HFC systems | Operates closer to conventional commercial refrigeration architecture, depending on refrigerant and system design |
| Installation complexity | Requires CO₂-rated components, pressure-rated piping, controls, valves, and service knowledge | Requires A2L-compatible equipment, charge-limit checks, leak detection assessment, ignition-risk control, and local code review |
| Warm-climate efficiency | Can require additional technologies such as parallel compression, ejectors, gas cooler optimisation, or advanced controls in warmer climates | Efficiency depends on refrigerant, system design, compressor selection, controls, and operating conditions |
| Serviceability | Requires technicians familiar with high-pressure CO₂ systems | Requires technicians trained for mildly flammable refrigerants and A2L service practices |
| Best fit | Projects prioritising very low GWP, non-flammability, and long-term refrigerant stability | Projects needing a lower-GWP transition path with a more conventional refrigeration system design |
| Key design checks | Pressure levels, controls, gas cooler performance, heat reclaim, ejector or parallel compression strategy, service expertise | Charge limits, equipment listing, leak detection, ventilation, electrical safety, ignition-source control, AHJ requirements |
When should I choose CO₂ for a walk-in cooler?
Choose CO₂ when the project prioritises a non-flammable refrigerant, very low GWP, and long-term refrigerant stability. CO₂ can be especially relevant for food retail and larger refrigeration architectures where the system design, controls, service expertise, and pressure-rated components are already part of the project plan.
CO₂ systems operate at higher pressures than many legacy refrigeration systems, so component selection and system design are different. Contractors should check whether the project has the required CO₂-rated compressors, valves, controllers, pressure sensors, piping, safety devices, and service capability.
In warmer climates, transcritical CO₂ systems may need additional efficiency measures. Technologies such as parallel compression and ejectors can help improve CO₂ system performance under high ambient conditions.
When should I choose A2L refrigerants for a walk-in cooler?
Choose an A2L refrigerant path when the project needs a lower-GWP refrigerant and a more conventional refrigeration architecture than CO₂. A2L refrigerants can be practical for selected commercial refrigeration applications, but they must be used only with equipment and components designed and approved for the selected refrigerant.
Because A2L refrigerants are mildly flammable, installers must check charge limits, room size, leak detection requirements, ventilation, ignition-source control, component compatibility, service procedures, and local code requirements. A2L systems should be planned as A2L-ready installations, not treated as simple like-for-like replacements for legacy HFC systems.
US regulatory considerations for A2L and CO₂ walk-in cooler systems
For US walk-in cooler and freezer applications, refrigerant selection should be checked against EPA SNAP use conditions, AIM Act-related HFC restrictions, equipment listing, safety standards, and local code adoption.
| Requirement area | What to check |
|---|---|
| EPA SNAP | Confirm whether the refrigerant is acceptable for the specific commercial refrigeration end use and under which use conditions. |
| AIM Act / Technology Transitions | Check whether the selected refrigerant and equipment strategy aligns with current and upcoming HFC restrictions. |
| UL 60335-2-89 | Confirm product safety requirements for commercial refrigeration equipment where applicable. |
| ASHRAE 15 | Check system safety requirements, including charge, location, ventilation, detection, and mitigation. |
| ASHRAE 34 | Confirm refrigerant safety classification, including A1, A2L, or A3. |
| AHJ requirements | Confirm local Authority Having Jurisdiction requirements before installation. |
| Equipment listing | Confirm the equipment is approved or listed for the selected refrigerant and application. |
| Service readiness | Confirm technician training, tools, documentation, labeling, and maintenance procedures. |
Practical selection guide: CO₂ or A2L for walk-in coolers?
| Project need | More likely fit |
|---|---|
| Lowest possible GWP and non-flammable refrigerant path | CO₂ / R744 |
| More conventional commercial refrigeration architecture | A2L refrigerant system |
| Larger food retail or multi-room refrigeration project | CO₂ may be relevant, depending on system architecture |
| Small to mid-size walk-in cooler with lower-GWP transition needs | A2L may be relevant where approved equipment is available |
| Warm-climate installation where CO₂ efficiency is a concern | CO₂ with additional efficiency technologies, or an A2L path depending on requirements |
| Contractor base already experienced with CO₂ systems | CO₂ may be easier to support |
| Contractor base more familiar with conventional HFC-style architecture | A2L may be easier to support, provided safety requirements are met |
| Existing legacy system retrofit | Evaluate lower-GWP A1 retrofit options first; do not treat A2L or CO₂ as simple drop-in replacements |
FAQ
CO₂ transcritical vs A2L for walk-in coolers
Is CO₂ or A2L better for commercial walk-in coolers?
There is no single best refrigerant for every commercial walk-in cooler. CO₂ is a strong option when very low GWP and non-flammability are priorities, but it requires high-pressure system design and CO₂-ready components. A2L refrigerants can offer a lower-GWP path with a more conventional system architecture, but they are mildly flammable and require charge-limit checks, leak detection assessment, equipment listing, and local code review.
Is CO₂ suitable for walk-in coolers in warm climates?
CO₂ can be used in warm climates, but transcritical CO₂ systems may need additional efficiency technologies to perform well at high ambient temperatures. Parallel compression, ejectors, gas cooler optimisation, and advanced controls can help improve performance in warmer conditions.
Are A2L refrigerants easier to install than CO₂?
A2L systems may be less complex than CO₂ systems from a pressure and system architecture perspective, but they still require careful safety planning. A2L refrigerants are mildly flammable, so installers must verify equipment listing, charge limits, room size, leak detection, ventilation, ignition-source control, and local code requirements.
Does CO₂ require different components than A2L systems?
Yes. CO₂ systems operate at higher pressures and require components designed for CO₂ operation, including pressure-rated valves, sensors, piping, compressors, controllers, and safety devices. A2L systems require components approved for the selected mildly flammable refrigerant and may require leak detection, safety shut-off logic, and additional mitigation depending on the system design.
Are A2L refrigerants approved for US walk-in cooler applications?
A2L refrigerants may be used in selected US commercial refrigeration applications when they meet EPA SNAP use conditions, equipment listing requirements, safety standards, and local code requirements. Installers should confirm the exact refrigerant, application, charge size, and equipment listing before specifying an A2L system.
Can an existing walk-in cooler be converted to CO₂ or A2L?
CO₂ and A2L refrigerants should not be treated as simple drop-in replacements for existing walk-in cooler systems. CO₂ requires a high-pressure system design, while A2L refrigerants require equipment designed and approved for mildly flammable refrigerants. Existing systems should first be evaluated for approved lower-GWP retrofit refrigerants, component compatibility, and long-term replacement planning.
IEC 60335-2-89
What are the new charge limits for flammable refrigerants under IEC 60335-2-89?
The charge limits have increased from 150g to 500g for the most flammable A3 refrigerants. For mildly flammable alternatives (A2 and A2L), the limit has increased from 150g to 1.2kg.
But the new, higher limits only apply to some applications, and only in rooms of a certain size. They will also take time to be reflected in revisions to national-level regulations.
When will the new charge limits come into force?
It’s difficult to tell, and it will vary between countries. This is because the international IEC standard is a voluntary international recommendation. To have any legal power, it will need to be reflected in each country’s local safety regulations like the ASHRAE standards, UL 60335-2-89 in the United States, EN 60335-2-89 in Europe, and China’s GB9237.
In many cases, standards are reviewed on a strict schedule, so there could be up to a five-year delay before the new limits are officially reflected in national law.
Is there a way to develop systems with the new, higher limits now?
Ultimately, manufacturers are responsible for the safety of the units they produce. In many countries, there is the option to conduct a separate risk assessment, outside of the local regulations – for example, under the European refrigeration standard EN 378.
Arguably, a manufacturer could use the new, international standard as justification for its risk assessment that – subject to the restrictions set out in the document – the new, higher limits are safe.
I heard the proposed increases had been rejected?
Initially, the IEC decided against the increases by one “no” vote. However, this “no” vote was later challenged and overturned.
The situation caused some confusion in the market, but the new limits have now been adopted by the IEC, and are included in the revised wording for IEC 60335-2-89.
Which refrigeration systems are covered by the new, higher charge limits?
The revised standard applies to electrically-operated commercial refrigerating appliances – including ice makers, for the first time. It also includes:
- Multi-desk display cabinets
- Glass door merchandisers
- Bottle coolers
- Serve-over cabinets
- Blast freezers
- Reach-in cabinets
- Gondola cabinets
- Gelato counters
- Preparation counters
- Ice-cream freezers
Draft beverage coolers are included if the compressor is integrated within the countertop housing, and is not external to the unit.
However, the revised standard does NOT apply to walk-in display coolers, ice-cream dispensers, water dispensers or walk-in cold rooms.
Appliances that include any refrigerating circuit with a refrigerant charge of 150g of flammable refrigerant or more are affected by the standard. As such they must be built and installed so their operation doesn’t cause excessive vibration or resonance points in the piping connected to the motor-compressor.
Compliance with the standard is assessed based on whether:
- The appliance is installed in line with installation instructions and is supplied at rated voltage or at the upper limit of the rated voltage range
- Supply frequency to any non-variable speed motor-compressors is varied in 1Hz steps between 0.9 times and 1.1 times the rated frequency
- The supply frequency from the inverter to variable speed motor-compressors is increased in 1Hz steps from minimum frequency to maximum frequency over the speed range in the appliance
- The vibration amplitude is measured at points in the piping with a large amplitude
- When measured with a low pass filter at 200Hz, vibrations stay below an acceleration of 0.3g RMS in refrigerant-containing parts
- Measurement sensors do not influence the line vibration level
Do the IEC 60335-2-89 rules place any restrictions on system design?
The revised IEC 60335-2-89 flammable refrigerant rules apply to appliances where the compressor is contained inside the main appliance housing.
Other restrictions include:
- Remote condensing units should not have more than 150g of flammable refrigerant in any one refrigerating circuit.
- Systems with flammable refrigerant must be hermetically sealed—so soldered connections are acceptable but flare connections are not. Other connections, such as O-rings and Schraeder service valves may be acceptable, depending on their design.
- The rules only apply to refrigerants with a molar mass of at least 30kg/kmol. That is, refrigerants that are heavier than air, so will sink if they leak.
- When the system runs, it should not generate excessive vibration in the compressor or the piping that leads to it. You’ll find more detail on how this is defined below.
Does the new limit apply to one circuit, or the whole system?
The flammable refrigerant charge limits in IEC 60335-2-89 are per circuit. It is possible to have a greater charge in a system if there are multiple circuits. This is considered safe, as the main risk is from a leak rather than an ignition in the system itself.
How are minimum room sizes calculated for a flammable refrigerant?
To prevent an explosive atmosphere in the case of a leak, units with charges above a certain limit can only be used in rooms exceeding a minimum floor size.
This room size is calculated based on the refrigerant charge, and the lower flammability limit (LFL) of the refrigerant. The manufacturer needs to display the restriction prominently, on a standard label complying with IEC 60417-6415.
The minimum room size (in m2) is equal to:
- the refrigerant charge (in kg), divided by
- one quarter of the LFL (in kg/m3) multiplied by 2.2 (the assumed height of the room)
So, for example, a system with 153g of R290 would require a minimum floor area of:
0.153kg / 2.2m x (0.25 x 0.038kg/m3) = 7.3m2
But a system with 494g of R290, the required area is much greater:
0.494kg / 2.2m x (0.25 x 0.038kg/m3) = 23.6m2
Whose responsibility is it to ensure the room size instructions are followed?
The manufacturer must ensure the calculations are correct and that the unit is labelled correctly, in a way that meets the standard. But it is the responsibility of the user to ensure the unit is installed in a way that complies with the regulations.
Can you have several flammable refrigerant units in one room?
Yes. The limit applies to each unit separately, and there is no need to divide the floor area between them. This is because the risk of several units leaking simultaneously—and therefore creating an explosive atmosphere—is very low.
How much vibration is acceptable under the revised IEC 60335-2-89?
IEC 60335-2-89 requires a system with more than 150g of flammable refrigerant to be designed in a way that does not generate excessive vibration or resonance in the piping to the compressor.
The standard sets a vibration limit of 0.3g RMS (measured with a low pass filter of 200 Hz) at 90% to 110% of the rated compressor frequency, or across the complete speed range of a variable speed compressor.
Do the new charge limits affect Pressure Equipment Directive (PED) approval?
No, the PED is unchanged, and systems being sold in Europe still need to comply. It’s worth noting that the PED does not differentiate between A2L and A3 refrigerants—the rules apply to all flammable refrigerants equally.
Who polices flammable refrigerant charge standards?
IEC 60335-2-89 is a voluntary international standard, that informs the local regulations in countries all around the world. Each country then enforces its own rules as usual.
What do service engineers need to know about flammable refrigerant rules?
Handling flammable refrigerants needs additional skills—and this is reflected in guidance which varies from one country to another. In the USA, it is highly recommended, in Europe, it is mandatory that flammable refrigerant systems are only serviced by technicians who have been specially trained. Some offer dedicated certification programs.
For more information on flammable refrigerant best practice and training, visit our refrigerant transition center.
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