Propane (R290) as a refrigerant: Where it is suitable for use in industrial refrigeration – and what the safety concept must achieve

Propane is one of the natural refrigerants that are becoming increasingly important in industrial refrigeration. Known as R290, it is used in chillers, heat pumps and combined cooling and heating systems. It has a very low global warming potential and offers good conditions for efficient operation. At the same time, propane is flammable. Whether R290 is suitable for a particular project therefore depends on the required temperatures, the cooling capacity, the installation site and the safety concept.

What makes propane stand out as a refrigerant

R290 has a global warming potential (GWP) of 0.02, calculated over a 100-year period. This is the value specified in Annex VI of Regulation (EU) 2024/573; it is based on the Sixth Assessment Report of the IPCC. Older publications often cite the value of 3 from the Fourth Assessment Report. By way of comparison: the scale is designed such that CO₂ is assigned a value of 1. Synthetic refrigerants, which have dominated the market for decades, are several orders of magnitude higher. For a system designed to operate for 15 years or more, this has a noticeable impact on refill quantities, servicing requirements and residual value. However, the refrigerant alone does not determine the carbon footprint. Leakage, energy consumption and the system’s power supply must also be taken into account.

From a thermodynamic perspective, propane is a highly effective refrigerant. How efficiently a system operates with it depends on its design and the operating conditions. A key parameter is the temperature difference between the cold and hot sides. Higher permissible chilled water temperatures reduce this range and take the strain off the compressor. Higher required heating temperatures increase it and reduce efficiency. The temperature requirements of the end-users must therefore be taken into account right from the start of the planning stage.

According to ASHRAE 34 and DIN EN 378, propane is classified in safety group A3 Classified as: low toxicity, highly flammable. This classification sets out the framework for capacity, location and safety measures. It therefore also determines which system architecture is suitable for a project.

Our page provides an overview of CO₂, ammonia and propane, including their technical specifications and areas of application at natural refrigerants.

‘Flammable’ means: the safety plan must come first

If released, propane can form a flammable mixture with air and, in high concentrations, displace oxygen. The gas is heavier than air. It accumulates in shafts, depressions and low-lying areas, even if the room in which the appliance is installed is well ventilated. Everything else follows from these properties.

A propane refrigeration system is designed with its safety concept in mind. That may sound like a restriction, but in practice it is primarily a question of sequence. Those who clarify the safety issues at the outset gain greater freedom in the design. Those who leave them until the end often end up having to do the design work twice.

Filling quantity per refrigeration circuit. The permissible fill level depends on the installation site, accessibility and ventilation. The applicable standards define categories for this purpose, which must be assessed for the specific project at the start of the planning process. This determines whether a cooling capacity can be achieved within a single circuit or must be distributed across several circuits.

Line-up. In many industrial projects, the plant room housing the propane chillers is erected outdoors. The refrigerant remains outside the user areas, and installation can be organised whilst operations continue. However, outdoor installation does not in itself guarantee that any escaping refrigerant will be adequately vented. Shafts, building openings, recesses and the actual air movement at the site must be assessed, as must potential ignition sources in the vicinity. Installation inside a building is possible, but requires a system and room layout specifically designed for this purpose, including ventilation and gas detection.

Indirect system. In most of KSI’s propane systems, the refrigerant remains in the technical centre. Cold water or cold brine flows to the consumers. No refrigerant-carrying pipes run through production areas, warehouses or server rooms. The hydraulic system thus forms part of the safety concept and can, at the same time, be designed with redundancy. It nevertheless remains an integral part of the safety assessment, for example in relation to heat exchangers and venting systems.

Security technology. Gas detection sensors in the correct locations, defined shut-off procedures, a design free from ignition sources in the installation room, and the ability to shut off individual circuits form part of the system and are specified during the planning stage. In addition, there is maintenance, testing and safe access to the components. Retrofitting is possible, but it is a complex process.

Where propane is suitable for industrial refrigeration

These properties give rise to typical areas of application.

• Chillers for process and building cooling. Compact chillers that supply a chilled water network are the most common application. The cooling capacity is distributed across several units, with the network handling the distribution.
• Heat pumps for simultaneous cooling and heating requirements. Propane is suitable for systems in which the hot side is also utilised. In plastics processing, for example, production requires both cooling and heating at the same time.
• Systems with a high proportion of free cooling. Data centres and systems with a year-round base load operate at higher flow temperatures. Propane maintains its efficiency at this temperature level, and the outdoor installation of the technical centre is in line with the free cooling concept.
• Standard refrigeration combined with CO₂ for deep-freezing. In projects involving both temperature levels, propane handles standard refrigeration, whilst CO₂ systems provide deep-freeze refrigeration . Each refrigerant is used where it is most effective.

Propane is less suitable in situations where high cooling capacities are required in a single circuit and the charge cannot be distributed across several units. In this area, ammonia has its place.

Free cooling and heat recovery: What the control system must achieve

Free cooling is not a property of propane. It utilises low outdoor temperatures to remove heat from the cold water or cold brine circuit, so that the compressor runs less, or at times not at all. Pumps and fans still require electricity. The proportion of free cooling achieved over the course of a year depends on the location, the system temperatures, the heat exchangers and the load profile. Propane is well-suited to this mode of operation because it maintains its efficiency at the higher flow temperatures that favour free cooling.

If heat is required at the same time, utilising the waste heat is usually more economical than discharging it into the environment. The control system must then take cooling demand, heating demand and outdoor conditions into account collectively and derive the operating point from this. In production facilities with simultaneous cooling and heating requirements, this is where the real potential of a combined system lies.

Multiple units: partial load and redundancy

With propane, the distribution of cooling capacity across several circuits or units is often dictated by the filling quantity limit. This offers further advantages: a staggered capacity delivery, improved part-load performance and the ability to service one unit whilst the others are running.

However, redundancy only arises as a result of the design. The crucial factor is how much capacity remains actually available in the event of a unit failing, and whether the pumps, hydraulics, control system and power supply are also protected. A chiller designed with redundancy is of little use if the shared distribution system is a single-loop design.

Refrigerant R290 and the F-Gas Regulation

Regulation (EU) 2024/573 gradually reduces the quantities of hydrofluorocarbon refrigerants (HFCs) available and sets out application-specific restrictions on equipment and refrigerants. The requirements applicable to a specific project depend on the application, the date of commissioning and the version of the Regulation in force at the time. This must be checked at the start of the planning process.

Propane is not a fluorinated greenhouse gas and is not subject to the HFC quota scheme. A A system using R290 can be operated and maintained with the same refrigerant throughout its entire service life, without availability or price being affected by shortages. This is an argument that goes beyond the investment costs, even at the planning stage. The requirements regarding safety, the qualifications of the specialist contractor and the operator’s obligations apply regardless of this and must still be verified.

Case study: Cooling and heating with propane in plastics production

KSI Kältetechnik has installed a central cooling and heating system for the production processes at the Zella-Mehlis site for a leading international company in the plastics industry. The system runs on propane and combines the refrigerant with heat pump technology.

The key facts:

• Refrigerant: R290 (propane)
• Cooling capacity: 2 × 318 kW
• Heating capacity: 2 × 403 kW
• Cooling capacity: 800 kW
• Redundancy: 100%, all pumps designed redundantly
• Operating mode: Cooling, heating and free cooling modes, controlled according to current demand
• Control system: Siemens central control system with visualisation and secure remote access
• Line-up: Outdoor technical centre, construction to take place alongside ongoing production
• Planning: entirely in 3D

The core of the concept lies in the simultaneous use of both sides of the heat pump. The cold side cools the processes, whilst the hot side supplies heat to where it is needed in production . What would otherwise be released into the environment via the recoolers is partly retained within the process. Free cooling supplements this during periods when the outside temperature allows for cooling without a compressor. Full details can be found in the Reference Uponor.

Two further installations illustrate the range. In the data centre of the NorthC Data centres in Munich Propane chillers with a cooling capacity of 1.0 MW and 100 per cent redundancy provide the centralised cooling, with dynamic switching between cooling and free cooling modes and integrated heat recovery. In the Maritim Hotel Amsterdam Six propane chillers provide standard cooling for 30 cold stores and other cold storage areas via chilled brine, whilst CO₂ systems handle deep-freeze cooling. The choice of refrigerant is always based on the requirements of the respective system.

Converting an existing system to propane

R290 can also be an option when modernising an existing refrigeration system. It is usually not simply a matter of replacing the refrigerant in the existing circuit: the compressor, heat exchanger, safety devices and installation must be suitable for propane. In practice, therefore, the focus is usually on replacing the refrigeration system, whilst assessing which parts of the existing infrastructure can continue to be used, such as the chilled water network, consumers, recoolers or building services.

Whether the conversion can be carried out whilst production continues depends on the existing infrastructure and a viable transition plan. At Uponor and NorthC, the new technical centre was built whilst operations continued and was only integrated afterwards. The page describes how KSI assesses and retrofits existing plants Regeneration and modernisation.

Key considerations when planning a propane refrigeration system

If you’re evaluating a proposal or a concept using R290, these questions will go a long way:

1. What temperatures do consumers require, and what are the implications for the temperature range? This is where a large proportion of the running costs is determined.
2. How is the capacity per district determined, and which installation category is used as a basis? The assumptions should be transparent and consistent with the actual installation site.
3. Does the refrigerant remain in the plant room? Indirect systems using cold water or cold brine keep the areas of use free from flammable substances.
4. Is the redundancy continuous? From refrigeration units, pumps, hydraulics and control systems – and not just for chillers.
5. How much free cooling and heat recovery has been calculated for the site, and on what basis? The assumptions should be clear and understandable.
6. How does the system behave at part load? Having several units offers advantages here if the control system makes use of them.
7. What security systems are in place, and who maintains them? Gas detection systems and shut-off devices require regular inspections, just like any other component.
8. Can maintenance be carried out during operation? The ability to lock off areas, accessibility and a switchover concept should be included in the planning.

How KSI Kältetechnik can help

KSI designs, builds and maintains industrial refrigeration systems using natural refrigerants – from energy planning and concept development through Installation and commissioning to technical support with 24/7 standby.

In an R290 project, temperature requirements, load profiles, installation and security of supply are considered together. This determines the choice of system between direct and indirect configurations, the distribution of cooling capacity across circuits and units, the safety concept including installation and gas detection technology, as well as the design for free cooling, heat recovery and demand-based control.