Natural Refrigerants in Heat Pumps

Natural refrigerants are naturally occurring, non-fluorinated substances used as the working fluid inside a heat pump. Common examples include propane, carbon dioxide, ammonia, isobutane, water, and air. The refrigerant absorbs heat at a low temperature and releases it at a higher temperature after compression.

The term natural refrigerant describes the origin and chemical family of the substance. It does not describe the heat source, efficiency, or safety of the heat pump. An air-source heat pump, for example, can use the natural refrigerant R290 or the fluorinated refrigerant R32.

The European Union identifies air, carbon dioxide, ammonia, hydrocarbons, and water as natural alternatives to fluorinated greenhouse gases. Hydrocarbons such as propane are considered natural because they occur in natural material cycles, even when refrigerant-grade material is produced through industrial processes.

Natural refrigerants at a glance

What are they?

Natural refrigerants are non-fluorinated working fluids such as propane R290, carbon dioxide R744, ammonia R717, isobutane R600a, and water R718.

What do they do?

They transport heat between the heat source and the building’s heating or hot-water system.

How are they used?

A building owner selects a heat pump that has been designed, tested, and approved for a specific natural refrigerant. Natural refrigerants must not be treated as universal replacement fluids for existing equipment.

Why do they matter?

They can reduce the direct climate impact of refrigerant leakage. They also reduce exposure to restrictions, quotas, and supply risks connected with fluorinated refrigerants. Their use still requires proper control of flammability, toxicity, pressure, charge, and installation conditions.

Key distinction: A natural refrigerant is not a renewable heat source. Air, ground, water, and waste heat provide environmental energy. The refrigerant transfers that energy through the heat pump.

What Is a Natural Refrigerant in a Heat Pump Environment?

A natural refrigerant is a substance found in natural material cycles that can change pressure, temperature, or physical state inside a refrigeration circuit. This behaviour allows the substance to absorb and release heat efficiently.

The refrigerant circulates inside a closed system. It is not normally consumed during heat-pump operation. Direct refrigerant emissions occur only when the substance escapes during a leak, repair, servicing process, accident, or decommissioning activity.

Natural refrigerants belong to several chemical groups:

• Hydrocarbons: propane R290, isobutane R600a, propylene R1270
• Inorganic refrigerants: carbon dioxide R744, ammonia R717, water R718
• Air-cycle refrigerants: air, commonly identified as R729 in refrigerant nomenclature

Natural refrigerant is an industry and technical term. It is not a single safety or efficiency classification. Different natural refrigerants have very different operating characteristics.

What natural refrigerants are not

A natural refrigerant is not automatically:

• Non-flammable
• Non-toxic
• Suitable for every building
• More efficient in every operating condition
• Compatible with existing compressors or pipework
• Safe for a refrigerant conversion
• A guarantee of low electricity consumption

The complete heat pump must be designed around the selected refrigerant. The compressor, heat exchangers, expansion device, seals, lubricant, pipework, pressure controls, electrical components, enclosure, and safety system must all be compatible.

Core Purpose of Natural Refrigerants

The core purpose of a natural refrigerant is to transport thermal energy through the heat-pump cycle. It enables a heat pump to collect low-temperature heat and deliver that heat at a useful temperature.

Natural refrigerants perform the same basic thermodynamic function as fluorinated refrigerants. Their main difference lies in their chemistry, climate impact, safety characteristics, operating pressure, and regulatory treatment.

How the natural refrigerant cycle works

1. Evaporation absorbs heat.
   The refrigerant enters the evaporator at low pressure. It absorbs energy from outdoor air, ground, groundwater, or waste heat.
2. Compression raises the temperature.
   The compressor increases the refrigerant pressure. This process also raises its temperature.
3. Heat transfer releases useful energy.
   The refrigerant transfers heat to the building’s heating water or domestic hot water. Most heat pumps use a condenser. Transcritical carbon dioxide systems often use a gas cooler instead.
4. Expansion lowers the pressure.
   The expansion device reduces the refrigerant pressure and temperature. The cycle then starts again.

Evaporation requires heat input, while compression raises the refrigerant to a temperature that can serve the building. This principle applies to both natural and fluorinated refrigerants.

Environmental purpose

Natural refrigerants provide a route away from high-global-warming-potential fluorinated gases. Their low direct climate impact becomes relevant when refrigerant escapes from the system.

Regulatory purpose

Natural refrigerants help manufacturers and building owners prepare for restrictions on fluorinated refrigerants. They can support long-term product availability and asset planning.

Operational purpose

Each natural refrigerant supports different operating conditions. R290 is widely used in building heat pumps. R744 can suit high domestic-hot-water demand. R717 is established in large industrial systems.

Why Natural Refrigerants Are Needed

The direct-emissions problem

A heat pump transfers environmental heat without combustion at the building. However, a refrigerant leak can create direct greenhouse gas emissions.

The scale of those emissions depends on:

• Refrigerant type
• Refrigerant charge
• GWP value
• Leakage rate
• Service losses
• Refrigerant recovery at end of life

A small leak of a high-GWP refrigerant can represent a significant quantity of carbon dioxide equivalent. Natural refrigerants normally have a GWP close to zero or, in the case of carbon dioxide, a reference GWP of one.

The regulatory problem

Regulation (EU) 2024/573 entered into force on 11 March 2024. It introduced a stronger HFC phase-down and a staged schedule of restrictions for new refrigeration, air-conditioning, and heat-pump equipment. The rules apply directly in Austria, Germany, Italy, Spain, Poland, Finland, and other EU Member States.

Important heat-pump milestones include the following:

These dates concern the placing of new equipment on the market. They do not automatically require every installed heat pump to stop operating on the relevant date. Servicing restrictions, refrigerant availability, equipment condition, and national obligations must be assessed separately. The regulation also includes safety-related exceptions under defined conditions.

Because natural refrigerants are non-fluorinated, they are not part of the HFC quota phase-down. However, the heat pump remains subject to product safety, electrical safety, pressure, fire-safety, building, installation, and service requirements. EU certification rules now also cover relevant alternatives to F-gases, including natural refrigerants.

The Swiss regulatory context

Switzerland is not governed directly by the EU F-gas Regulation. Refrigerants are regulated through Annex 2.10 of the Swiss Chemical Risk Reduction Ordinance, known as ORRChem or ChemRRV.

The Swiss framework aims to reduce emissions from ozone-depleting and strongly climate-warming refrigerants. It is updated to follow technical progress and developments in European regulation. A project in Switzerland must therefore be checked against the current Swiss provisions rather than treated automatically as an EU project.

The business problem

A heat pump is a long-life building asset. A refrigerant decision can affect service availability, repair costs, portfolio compliance, procurement criteria, and future replacement planning.

A poorly selected system can expose a building owner to:

• Restricted future product choices
• Higher refrigerant costs
• Limited service capacity
• Difficult component replacement
• Premature asset replacement
• Safety-related installation changes
• Failure to meet environmental procurement requirements

Natural refrigerants can reduce some of these risks. They do not remove the need for correct system design.

The whole-system performance problem

A low-GWP refrigerant does not compensate for poor sizing, high flow temperatures, excessive cycling, weak insulation, or inefficient controls. The heat pump’s electricity use must be assessed alongside direct refrigerant emissions.

The correct goal is not simply to select the refrigerant with the lowest GWP. The goal is to select a safe, efficient, serviceable, and regulation-ready heat-pump system.

Key Features of Natural Refrigerants

Detailed Explanation of Natural Refrigerant Features

Non-fluorinated composition

Definition:
A non-fluorinated refrigerant does not contain fluorine as part of an HFC or HFO refrigerant molecule. Natural refrigerants include hydrocarbons and inorganic substances.

Purpose:
The composition separates these refrigerants from gases controlled through the EU HFC quota phase-down.

Benefits:
The system has less exposure to future HFC availability and quota-related market pressure. It also avoids direct emissions from high-GWP fluorinated gases.

Example:
R290 is a hydrocarbon refrigerant. It is used in factory-designed residential and commercial heat pumps.

Very low global warming potential

Definition:
Global warming potential compares the warming effect of a released substance with the effect of carbon dioxide over a defined period.

Purpose:
GWP allows planners to calculate direct refrigerant emissions as carbon dioxide equivalent.

Benefits:
A low-GWP refrigerant reduces the direct climate consequence of leakage. It can also support environmental procurement and carbon reporting.

Example:
Under the GWP values used by the European Commission for Regulation (EU) 2024/573, R290 has a 100-year GWP of 0.02. R744 has a GWP of 1. Older documents may show different values because they use earlier scientific assessment reports.

Zero ozone-depletion potential

Definition:
Ozone-depletion potential measures the ability of a substance to damage the stratospheric ozone layer.

Purpose:
The metric distinguishes modern refrigerants from older CFC and HCFC substances such as R12 and R22.

Benefits:
Natural refrigerants such as R290, R744, R717, R600a, and R718 have no ozone-depletion effect.

Example:
Selecting an R290 heat pump avoids both the ozone impact of older refrigerants and the high direct climate impact of many legacy HFCs.

Safety classification

Definition:
ISO 817 classifies refrigerants according to toxicity and flammability. The letter indicates toxicity class. The number indicates flammability class.

• A: Lower toxicity
• B: Higher toxicity
• 1: No flame propagation under the standard test
• 2L: Lower flammability with low burning velocity
• 2: Lower flammability
• 3: Higher flammability

Purpose:
The safety class provides a common basis for equipment design, charge limits, room-volume calculations, installation conditions, and service procedures.

Benefits:
A clear classification allows manufacturers and installers to apply the correct risk controls.

Example:
R290 is A3 because it has lower toxicity and higher flammability. R744 is A1. R717 is B2L because ammonia has higher toxicity and lower flammability. A1 does not mean risk-free; pressure, asphyxiation, and confined-space risks can still apply.

Pressure-temperature behaviour

Definition:
Each refrigerant has a specific relationship between pressure, temperature, density, and physical state.

Purpose:
This relationship determines the compressor design, heat-exchanger size, pipe strength, expansion control, and operating envelope.

Benefits:
A refrigerant matched to the application can transfer heat efficiently across the required temperature lift.

Example:
R744 operates at much higher pressure than most building heat-pump refrigerants. R718 can operate under vacuum and requires large refrigerant volume flow. These characteristics require purpose-built components rather than a simple fluid substitution.

Temperature capability

Definition:
Temperature capability describes the source and delivery temperatures within which the refrigerant circuit can operate safely and efficiently.

Purpose:
It determines whether the heat pump can serve underfloor heating, radiators, domestic hot water, industrial process heat, or district-heating networks.

Benefits:
Correct matching prevents excessive compressor stress and poor seasonal performance.

Example:
R290 is used in building heat pumps capable of elevated flow temperatures. R744 is established in domestic-hot-water and commercial applications. R717 is frequently used in medium and large industrial systems. Actual temperature limits remain product-specific.

Energy efficiency

Definition:
Energy efficiency measures how much useful heat the heat pump delivers for each unit of electrical energy consumed.

Purpose:
Efficiency determines operating costs, grid demand, and most of the indirect climate impact.

Benefits:
A well-designed natural-refrigerant heat pump can combine low direct emissions with low electricity use.

Example:
Two R290 heat pumps can have different seasonal efficiencies because they use different compressors, heat exchangers, defrost strategies, controls, and hydraulic designs. Refrigerant identity alone does not determine the SCOP.

Refrigerant charge and containment

Definition:
Refrigerant charge is the mass of refrigerant contained in the heat-pump circuit.

Purpose:
Charge control limits the possible consequences of a leak. Compact heat exchangers, short circuits, factory joints, and hermetic components can reduce the required charge.

Benefits:
A lower and well-contained charge can simplify risk management and reduce potential direct emissions.

Example:
An outdoor R290 monoblock normally keeps the sealed refrigerant circuit outside. Water pipes, rather than refrigerant pipes, connect the outdoor unit to the building. The installation must still respect the manufacturer’s defined safety area.

System architecture

Definition:
System architecture describes how the refrigerant circuit, water circuit, indoor equipment, and outdoor equipment are arranged.

Purpose:
The architecture controls where the refrigerant is located and where a leak could occur.

Benefits:
The correct design can separate occupants from the refrigerant circuit, reduce field-made joints, and simplify commissioning.

Example:
A self-contained heat pump is factory-made and does not require gas-containing components to be connected on site. A split system requires refrigerant connections between units.

Material and lubricant compatibility

Definition:
Material compatibility means that the refrigerant, lubricant, metals, seals, motor insulation, and other components can operate together without harmful chemical or mechanical effects.

Purpose:
Compatibility protects circuit tightness, heat transfer, lubrication, and compressor life.

Benefits:
Approved components reduce premature failure and unplanned leakage.

Example:
A compressor approved for R32 cannot be assumed suitable for R290. Pressure range, lubricant behaviour, electrical protection, displacement, and safety controls may differ.

Qualified installation and servicing

Definition:
Qualified handling means that installation, maintenance, repair, recovery, and decommissioning are completed by people trained for the relevant refrigerant and equipment.

Purpose:
Training addresses flammable gases, toxic gases, high-pressure systems, evacuation, leak testing, recovery, and emergency procedures.

Benefits:
Qualified service reduces accident risk and protects warranty, performance, and system life.

Example:
Commission Implementing Regulation (EU) 2024/2215 establishes certification requirements covering stationary heat-pump equipment containing F-gases or relevant alternatives, including natural refrigerants.

Types of Natural Refrigerants Used in Heat Pumps

The following values use the European Commission’s current GWP basis for Regulation (EU) 2024/573. GWP values in older technical literature may differ.

The European Commission identifies R290 and R744 as alternatives for domestic self-contained heat pumps. It also identifies R290, R744, and R717 for industrial heat pumps. R600a is established mainly in compact sealed refrigeration systems, while R718 remains a specialist option.

Propane R290

R290 is currently the most relevant natural refrigerant for many European residential heat pumps. It has favourable thermodynamic properties and can support high delivery temperatures in suitable system designs.

Its A3 classification means the complete system must control ignition risk. Manufacturers use low-charge circuits, sealed components, protected electrics, ventilation concepts, outdoor placement, and specified safety areas.

R290 is not the same product as fuel gas supplied for barbecues or heating, even though the principal molecule is propane. Heat pumps require refrigerant-grade material of the required purity. Building owners must never refill an R290 heat pump from a fuel cylinder.

Isobutane R600a

R600a is a hydrocarbon with a very low direct climate impact. It is widely established in refrigerators and small sealed equipment.

It has a lower volumetric heating or cooling capacity than R290. This property can require a larger compressor displacement for the same output.

R600a is therefore more common in compact applications than in high-output building heating systems. Like R290, it has an A3 safety classification.

Carbon dioxide R744

R744 is non-flammable and classified A1. It has a GWP of one because carbon dioxide is the reference gas used by the GWP metric.

Carbon dioxide systems operate at high pressure. Many operate transcritically, which means heat is released through a gas cooler rather than conventional condensation during part of the cycle.

R744 can be effective when water must be heated through a large temperature range. It is used in hot-water heat pumps, commercial refrigeration, heat recovery, and selected industrial systems.

Ammonia R717

R717 has been used in industrial refrigeration for many years. It offers strong thermodynamic performance in appropriately designed large systems.

Its B2L classification reflects higher toxicity and lower flammability. Plant-room design, gas detection, ventilation, emergency procedures, materials, and operator competence require close attention.

Ammonia is generally more relevant to industrial heat pumps, food production, large commercial plants, waste-heat recovery, and district-energy applications than to individual homes.

Water R718

Water can operate as a refrigerant in specialised systems. It is non-flammable, has lower toxicity, and has no direct global-warming effect as a refrigerant.

Its physical properties create engineering challenges. Low vapour pressure can require vacuum operation, while low volumetric capacity requires compressors capable of large volume flows.

R718 is therefore a specialist refrigerant rather than a mainstream choice for residential heat pumps.

Air

Air can act as the working fluid in an air-cycle heat pump. It is available, non-fluorinated, and does not create a conventional refrigerant-leak climate impact.

Air-cycle technology differs from the common vapour-compression systems used in hydronic building heat pumps. It is mainly relevant to specialist transport, aerospace, low-temperature, or process applications.

Natural-Refrigerant Heat-Pump Models and Architectures

Monoblock heat pump

Definition:
A monoblock contains the main refrigerant circuit within one factory-assembled unit.

Purpose:
It limits field-made refrigerant connections and can keep the refrigerant outside the occupied building.

Benefits:
The installer normally connects heating water rather than refrigerant pipework. This can simplify refrigerant containment.

Example:
An outdoor R290 air-to-water monoblock transfers heat to water pipes entering the building.

Split heat pump

Definition:
A split system uses separate indoor and outdoor units connected by refrigerant lines.

Purpose:
It separates system components and can reduce the risk of freezing water pipes outside.

Benefits:
The architecture can provide installation flexibility.

Example:
A split system may place the evaporator and compressor outside while locating the condenser or hydraulic module inside. The refrigerant joints require suitable installation competence.

Indirect or secondary-circuit system

Definition:
An indirect system keeps the refrigerant inside a packaged unit and transfers heating or cooling through water, brine, or another secondary fluid.

Purpose:
It prevents refrigerant from circulating throughout the occupied building.

Benefits:
The design can limit refrigerant charge and make hydrocarbons or ammonia practical in larger buildings.

Example:
An R290 chiller can produce chilled water for fan coils rather than sending refrigerant to every room.

Cascade and multi-unit systems

Definition:
A cascade or multi-unit system combines two or more heat-pump stages or units.

Purpose:
The arrangement can increase capacity, provide redundancy, or achieve a larger total temperature lift.

Benefits:
Operators can stage output according to demand and maintain partial operation during service.

Example:
A hotel or apartment complex can use multiple heat pumps with lead-lag control to serve space heating and domestic hot water.

Natural Refrigerant Use Cases

New single-family homes

A new home commonly has low-temperature underfloor heating and a modest heating load. These conditions suit efficient heat-pump operation.

An R290 air-to-water or ground-source heat pump can combine low direct refrigerant impact with low flow temperatures. The system should still be sized from a building heat-loss calculation.

Business relevance: The owner gains a heating asset aligned with the long-term move away from fluorinated refrigerants.

Renovations with existing radiators

Older buildings may require higher flow temperatures than new buildings. A natural-refrigerant heat pump can still be suitable when the building load, radiator output, hydraulic balance, and temperature requirement are assessed correctly.

Some R290 heat pumps can provide elevated flow temperatures. However, the highest possible temperature should not be used as the normal design target. Lowering the required flow temperature normally improves efficiency.

Practical application: Improve insulation, replace selected radiators, balance the system, and optimise the heating curve before relying on very high supply temperatures.

Apartment buildings

Apartment buildings combine larger space-heating loads with significant domestic-hot-water demand. They may also require redundancy and separate temperature zones.

Natural-refrigerant systems can use multiple heat pumps, central storage, decentralised transfer stations, or cascade control.

Business relevance: Housing operators can reduce direct refrigerant exposure across a large property portfolio and plan equipment replacement around EU market restrictions.

Hotels and buildings with high hot-water demand

Hotels require predictable domestic hot water throughout the day. Peak demand, storage temperature, circulation losses, hygiene strategy, and recovery time all affect the design.

R290, R744, or larger industrial heat-pump systems may be considered, depending on capacity and temperature profile.

Practical application: A heat pump charges stratified storage during low-demand periods and uses intelligent control to prepare for expected occupancy peaks.

Commercial buildings

Offices, schools, retail buildings, and mixed-use properties may require heating and cooling. A packaged natural-refrigerant heat pump or chiller can serve a water-based distribution system.

The indirect circuit keeps the refrigerant in a controlled location. Fan coils, chilled ceilings, underfloor systems, or air-handling units receive heating or cooling water.

Business relevance: The owner can replace distributed refrigerant circuits with a central low-GWP system.

Industrial heat recovery

Industrial sites often reject usable heat from refrigeration, production, compressed air, wastewater, or data-processing equipment. A heat pump can raise this heat to a useful process or network temperature.

R717, R744, R290, and other application-specific refrigerants can be considered. The correct choice depends on the heat-source temperature, output temperature, capacity, and site safety requirements.

Large heat pumps using R290, R744, R717, and related non-halogenated refrigerants are already used in European industrial applications.

District and local heating

A district or local heating system may use wastewater, groundwater, geothermal energy, industrial waste heat, or ambient heat.

Natural refrigerants can support central heat-pump plants, especially where high capacity justifies specialist pressure, plant-room, and safety engineering.

Practical application: Multiple units operate in stages and charge a network buffer according to heat demand and electricity availability.

Cold-climate applications

Austria, Germany, Switzerland, Poland, and Finland experience periods of low outdoor temperature. An air-source heat pump must therefore be evaluated at the local design temperature.

The refrigerant is only one factor. Compressor operating limits, defrost control, fan performance, backup-heater strategy, drainage, and emitter temperature affect the result.

Selection rule: Compare declared capacity and COP at the actual design condition, not only at the common A7/W35 rating point.

Warm-climate heating and cooling

Spain, Northern Italy, and warmer European regions may have larger cooling loads and higher summer ambient temperatures.

The system must be assessed in both heating and cooling modes. Condensing or gas-cooler conditions, part-load performance, humidity control, and heat rejection become important.

Selection rule: Use seasonal heating and cooling data for the relevant climate zone.

Benefits of Natural Refrigerants

Lower direct climate impact

Natural refrigerants normally have GWP values between zero and one under the current EU calculation basis. Leakage therefore creates much less direct carbon dioxide equivalent than leakage of high-GWP HFC refrigerants.

A German Environment Agency study found that natural-refrigerant heat pumps could reduce total greenhouse gas emissions by up to 17% in the modelled comparisons with conventional HFC heat pumps. The exact result depends on system efficiency, leakage, electricity mix, and lifecycle assumptions.

Greater regulatory resilience

Natural refrigerants are not controlled through the HFC quota phase-down. A natural-refrigerant product can therefore reduce exposure to the EU restrictions that progressively affect new F-gas heat pumps.

Lower refrigerant-supply exposure

HFC quotas and product prohibitions can affect the long-term availability and price of fluorinated refrigerants. A non-fluorinated system reduces dependence on that market.

Reduced refrigerant-linked carbon liability

Businesses that calculate direct operational emissions can report refrigerant losses as carbon dioxide equivalent. A very-low-GWP refrigerant limits the size of this emissions source.

Long-term asset planning

Buildings frequently remain in use for decades. A heat-pump system aligned with long-term regulatory direction may reduce the risk of early replacement caused by refrigerant obsolescence.

High-temperature options

Some natural-refrigerant heat pumps can deliver elevated flow or hot-water temperatures. This characteristic can support renovations, hotels, apartment buildings, and selected industrial processes.

High temperature capability does not guarantee high efficiency. The system should always operate at the lowest temperature that meets the building’s needs.

Strong environmental procurement position

Public authorities, housing providers, developers, and companies increasingly evaluate refrigerant type alongside energy efficiency. A natural refrigerant can support low-GWP procurement requirements and environmental building assessments.

Potential for efficient operation

Natural refrigerants can provide strong thermodynamic performance when the equipment is designed for the application. The final efficiency still depends on the complete product and system.

Limitations and Trade-Offs

Natural refrigerants should not be presented as risk-free substances. Each option shifts the engineering challenge rather than removing it.

Flammability

R290 and R600a are A3 refrigerants. Equipment design and installation must prevent a leak from reaching an ignition source at a hazardous concentration.

Typical controls include:

• Low refrigerant charge
• Factory-sealed circuits
• Protected electrical components
• Controlled ventilation
• Defined outdoor safety areas
• Separation from openings, drains, shafts, and ignition sources
• Refrigerant-aware service procedures

Exact distances must come from the current manufacturer documentation and applicable local rules.

Toxicity

R717 requires controls for toxicity. Larger systems may need gas detection, emergency ventilation, restricted plant access, alarms, and defined incident procedures.

High pressure

R744 systems need components, tools, and service procedures designed for high pressure. A1 classification does not remove pressure-related risk.

Installation constraints

An R290 outdoor unit may not suit every narrow courtyard, light well, façade, property boundary, or area close to doors and windows. Site assessment must take place before product selection is finalised.

Specialist service capacity

Natural-refrigerant systems require technicians with relevant knowledge and equipment. Commercial and industrial projects must verify local service availability before procurement.

Product-specific performance

The use of R290, R744, or R717 does not by itself prove high efficiency. Seasonal performance, operating range, sound, defrost, modulation, and hydraulic integration remain model-specific.

How to Select a Natural-Refrigerant Heat Pump

Step 1: Define the heating service

Identify whether the system must provide:

• Space heating
• Domestic hot water
• Active cooling
• Passive cooling
• Pool heating
• Process heat
• Simultaneous heating and cooling

The service definition determines the required temperatures and operating hours.

Step 2: Calculate the building heat load

Use a recognised room-by-room or building heat-loss calculation. Do not size the heat pump from floor area, boiler rating, or historic fuel use alone.

Correct sizing reduces cycling, backup-heater use, noise, and unnecessary capital cost.

Step 3: Determine the required flow temperature

Measure or calculate the flow temperature required at the local winter design condition. Assess radiator output, underfloor circuits, ventilation coils, and domestic-hot-water temperature separately.

The lowest practical flow temperature normally gives the best heat-pump efficiency.

Step 4: Select the heat source

Compare:

• Outdoor air
• Ground loops
• Groundwater
• Surface water
• Wastewater
• Industrial waste heat
• Exhaust air
• Hybrid sources

The heat source affects seasonal efficiency, investment cost, permitting, sound, defrost, and available capacity.

Step 5: Match the refrigerant to the application

A practical first shortlist is:

• R290: Residential and commercial building heat pumps
• R744: High hot-water demand and large water-temperature rise
• R717: Large industrial and district-energy systems
• R600a: Small sealed systems
• R718: Specialist large-volume-flow systems

The shortlist must then be validated against actual equipment performance.

Step 6: Select the architecture

Decide whether the project needs:

• Outdoor monoblock
• Indoor packaged system
• Split system
• Secondary water or brine circuit
• Multi-unit installation
• Cascade system

Architecture affects refrigerant location, frost risk, site layout, and service requirements.

Step 7: Complete a safety and siting assessment

Check:

• Refrigerant safety class
• Refrigerant charge
• Outdoor or indoor location
• Room volume
• Ventilation
• Openings and air inlets
• Drains, shafts, and light wells
• Ignition sources
• Escape routes
• Public access
• Fire-safety requirements
• Manufacturer safety area

Do this assessment before fixing the equipment location.

Step 8: Compare seasonal performance

Compare products at equivalent conditions. Review:

• SCOP for the relevant climate
• COP at winter design conditions
• Available output at low source temperature
• Output at required flow temperature
• Part-load performance
• Minimum modulation
• Defrost strategy
• Auxiliary electricity
• Domestic-hot-water efficiency
• Sound power

A high brochure COP at A7/W35 does not prove strong performance at A−7/W55.

Step 9: Check regulatory and service readiness

Confirm:

• Product conformity
• Applicable national rules
• Installer qualification
• Local service coverage
• Spare-parts strategy
• Refrigerant recovery procedure
• Warranty conditions
• Monitoring and fault support

Step 10: Design the complete energy system

The heat pump must be integrated with emitters, storage, pumps, valves, domestic hot water, cooling, photovoltaics, controls, and the electrical connection.

The refrigerant is one component of this system. It cannot correct a poor hydraulic or control design.

Natural Refrigerant Procurement Checklist

Before selecting a product, ask the supplier:

1. Which refrigerant does the heat pump use?
2. What is the refrigerant safety class?
3. What is the total refrigerant charge?
4. Is the circuit hermetically sealed at the factory?
5. Are refrigerant connections completed on site?
6. What outdoor or indoor safety area is required?
7. What heating output is available at the local design temperature?
8. What COP is achieved at the required flow temperature?
9. What is the maximum continuous flow temperature?
10. How is domestic hot water produced?
11. How does the system manage defrosting?
12. What is the minimum compressor modulation?
13. Which service qualifications are required?
14. Is trained service support available locally?
15. How is refrigerant recovered at end of life?
16. Can the controller integrate PV, storage, tariffs, or building management?
17. Does the product meet current market and safety requirements?
18. Are the quoted values supported by a current technical data sheet?

Natural Refrigerants Compared with Fluorinated Refrigerants

Natural does not mean safer

R290 has much lower GWP than R32, but it also has a higher flammability classification. R744 is non-flammable but operates at high pressure. R717 can be efficient in large plants but presents a toxicity hazard.

The correct comparison must therefore cover climate, safety, performance, architecture, and service together.

R290 Compared with R32

R290 has a much lower direct climate impact. R32 is less flammable but remains a fluorinated greenhouse gas with a GWP of 675 under the current EU basis.

Neither refrigerant guarantees higher seasonal efficiency. Compare complete products under the same source and water-temperature conditions.

R290 Compared with R744

R290 is often the more direct choice for conventional hydronic building heating. R744 can be attractive where cold water must be heated through a large temperature rise.

R290 Compared with R717

R290 is usually more suitable for compact building products. R717 is well established where project scale supports specialist industrial design and operation.

Natural Refrigerant Versus High Efficiency

Natural refrigerant and high efficiency are separate product attributes. A heat pump can use a very-low-GWP refrigerant and still perform poorly because of incorrect sizing, high flow temperature, poor control, or unsuitable hydraulic integration.

The selection order should be:

1. Confirm that the product can serve the load and temperature.
2. Confirm that the installation can be completed safely.
3. Compare seasonal efficiency at relevant conditions.
4. Assess refrigerant GWP and regulatory resilience.
5. Verify service, controls, sound, and lifecycle support.

The strongest environmental result combines:

• A natural or very-low-GWP refrigerant
• High seasonal efficiency
• Low refrigerant charge
• Reliable containment
• Low building heat demand
• Low flow temperature
• Renewable or low-carbon electricity
• Intelligent operation
• Correct refrigerant recovery

Integration with Other Heat-Pump Systems

Integration with the heat source

Definition:
The heat source supplies low-temperature environmental or waste heat to the evaporator.

Purpose:
It determines the temperature and stability of the energy entering the refrigerant cycle.

Benefits:
A stable, warm source reduces the required compressor temperature lift.

Example:
A ground-source R290 heat pump can receive more stable winter source temperatures than an air-source unit.

Integration with heat distribution

Definition:
Heat distribution transfers energy from the heat pump to rooms through underfloor heating, radiators, fan coils, or air systems.

Purpose:
The distribution system defines the required flow temperature and water flow.

Benefits:
Large emitters and balanced circuits allow lower temperatures and higher efficiency.

Example:
Replacing selected radiators can reduce the design flow temperature from 65°C to 50°C.

Integration with domestic hot water

Definition:
Domestic-hot-water integration connects the heat pump to a cylinder, fresh-water station, or other hot-water system.

Purpose:
It supplies showers, sinks, kitchens, and other sanitary uses.

Benefits:
Correct storage volume and control reduce electric backup use and unnecessary high-temperature operation.

Example:
The controller charges the upper cylinder zone for immediate demand while preserving lower-temperature water for efficient heat-pump operation.

Integration with buffer storage

Definition:
A buffer tank stores heating or cooling water between the heat pump and distribution system.

Purpose:
It can provide hydraulic separation, minimum water volume, defrost energy, or load shifting.

Benefits:
Correctly designed storage can stabilise operation and support flexible electricity use.

Example:
The heat pump raises the buffer temperature slightly while photovoltaic power is available.

A buffer tank should solve a defined hydraulic or control problem. An oversized or poorly connected buffer can increase heat losses and operating temperature.

Integration with cooling

Definition:
A reversible heat pump changes the refrigerant cycle to remove heat from the building.

Purpose:
It provides summer comfort from the same thermal system.

Benefits:
One system can provide heating, cooling, and hot water.

Example:
An R290 air-to-water heat pump supplies chilled water to fan coils while managing condensation limits.

Integration with photovoltaics

Definition:
PV integration coordinates heat-pump operation with on-site solar electricity.

Purpose:
It shifts suitable heating, cooling, or hot-water loads toward periods of solar generation.

Benefits:
The building can increase self-consumption and reduce grid imports.

Example:
The controller preheats domestic hot water or a buffer when surplus PV electricity is available.

Integration with energy management

Definition:
Energy management coordinates the heat pump with weather data, tariffs, storage, zones, and other energy devices.

Purpose:
It selects efficient operating times while maintaining comfort.

Benefits:
The system can reduce operating costs without changing the refrigerant or heat-pump hardware.

Example:
Predictive control delays a flexible storage charge until lower-cost electricity or solar generation is expected.

Integration with building management systems

Definition:
A building management system supervises multiple heating circuits, pumps, valves, meters, alarms, and heat generators.

Purpose:
It coordinates the heat pump with the wider building.

Benefits:
Facility managers receive central monitoring, fault information, and energy data.

Example:
A hotel BMS enables heat-pump stages according to cylinder temperatures, room demand, and available electrical capacity.

Integration with cascade systems

Definition:
Cascade integration coordinates several heat pumps or temperature stages.

Purpose:
It increases capacity, efficiency, redundancy, or temperature lift.

Benefits:
The controller can distribute operating hours and retain partial output during maintenance.

Example:
Three natural-refrigerant heat pumps operate in sequence as an apartment complex moves from low night demand to the morning hot-water peak.

How to Implement a Natural-Refrigerant Heat Pump

Establish the project conditions

Document the building load, source temperature, flow temperature, domestic-hot-water demand, cooling demand, electrical capacity, and available installation space.

Select purpose-built equipment

Choose a heat pump designed and approved for the natural refrigerant. Do not select the refrigerant separately from the equipment.

Confirm the installation location

Check sound, airflow, maintenance access, drainage, snow, flooding, openings, ignition sources, and the manufacturer’s refrigerant safety area.

Complete hydraulic design

Specify flow rates, pipe sizes, pumps, valves, buffer arrangement, emitters, domestic hot water, frost protection, and water quality.

Plan electrical and control integration

Confirm supply capacity, protection devices, backup heating, smart-grid signals, PV interfaces, meters, and building-management communication.

Use qualified installers

The installer must understand the refrigerant, equipment architecture, pressure testing, leak control, evacuation, charging restrictions, and commissioning process.

Commission the complete system

Commissioning should verify:

• Refrigerant-circuit integrity where applicable
• Heating-water flow
• Heating curve
• Compressor modulation
• Defrost operation
• Domestic-hot-water settings
• Backup-heater control
• Pump and valve function
• Safety devices
• Alarms
• Energy monitoring
• User instructions

Monitor operation

Review electricity consumption, heat output, flow temperature, compressor starts, backup-heater hours, faults, and seasonal performance.

Maintain the safety area

Building changes can affect a compliant installation. Owners should not add enclosures, sheds, drains, electrical equipment, air inlets, or other obstructions around the unit without checking the product requirements.

Plan end-of-life recovery

Natural does not mean that deliberate refrigerant release is good practice. Decommissioning should follow the manufacturer’s procedure and applicable recovery, transport, and waste rules.

Do not convert an existing heat pump to R290, R744, or another refrigerant unless the manufacturer has expressly approved the conversion. Refrigerants are not interchangeable operating fluids.

Standards and Technical Reference Framework

Common technical reference points include:

• ISO 817:2024: Refrigerant designation and safety classification
• EN 378-1:2016+A1:2020: Basic safety and environmental requirements for refrigeration systems and heat pumps
• IEC 60335-2-40:2024: Particular safety requirements for electric heat pumps, air conditioners, and dehumidifiers
• Regulation (EU) 2024/573: EU rules for fluorinated greenhouse gases
• Commission Implementing Regulation (EU) 2024/2215: Certification requirements for equipment containing F-gases or relevant alternatives

ISO 817 establishes the classification system. EN 378 addresses system-level safety and environmental requirements. IEC 60335-2-40 addresses product hazards for relevant heat-pump and air-conditioning equipment. Applicability depends on the product, national adoption, legal framework, and project conditions.

Standards do not replace the manufacturer’s installation documentation. The stricter applicable requirement must be followed where requirements overlap.

iDM treats the refrigerant as part of a complete thermal energy system. The correct solution begins with the building load, heat source, flow temperature, hot-water demand, distribution system, and control strategy.

The iDM iPUMP A ONE series uses R290 and combines heating, active cooling, and domestic-hot-water production. Current product information states flow temperatures of up to 70°C and an integrated 320-litre hot-water tank. The iPUMP T7 ONE uses R290 with geothermal energy or groundwater and can also achieve flow temperatures of up to 70°C. Product availability and technical data can vary by model and market.

The refrigerant decision should then be supported by intelligent operation. iDM’s NAVIGATOR energy-management environment can coordinate heating, cooling, domestic hot water, photovoltaic generation, zones, and other system functions. Predictive control can also respond to weather, electricity prices, PV output, and user behaviour.

This creates a complete decision chain:

Natural refrigerant → correctly sized heat pump → low-temperature distribution → intelligent control → renewable electricity integration → lower lifecycle impact

Frequently Asked Questions About Natural Refrigerants

Are natural refrigerants safe?

Natural refrigerants can be used safely in equipment designed for them. Their risks differ. R290 is flammable, R717 is toxic and mildly flammable, and R744 operates at high pressure. Safety depends on equipment design, charge, siting, installation, controls, and qualified service.

Is R290 the same as propane?

R290 is propane used as a refrigerant. Heat pumps require refrigerant-grade propane with controlled purity. Fuel-grade propane cylinders must not be used to service a heat pump.

Is a natural refrigerant always better than R32?

R290 has a much lower GWP than R32, but it has a higher flammability classification. The complete comparison must include safety, seasonal performance, location, architecture, service, and regulation.

Can an existing R32 or R410A heat pump be converted to R290?

Generally, no. The compressor, electrical protection, heat exchangers, controls, pipework, lubricant, and safety design may not be compatible. A conversion should only occur under an explicit manufacturer-approved process.

Do natural refrigerants reduce electricity consumption?

Not automatically. Electricity consumption depends on the complete heat-pump design and its integration with the building. Compare SCOP, design-condition COP, modulation, flow temperature, controls, and auxiliary loads.

Which natural refrigerant is best for a residential heat pump?

R290 is currently the most common natural-refrigerant option for many European residential hydronic heat pumps. The best product still depends on the building, location, heat source, and temperature requirement.

Which natural refrigerant is best for domestic hot water?

R290 and R744 can both serve domestic-hot-water applications. R744 can be particularly relevant where water is heated through a large temperature range. Product efficiency must be checked at the actual water conditions.

Which natural refrigerant is best for industry?

R717, R744, and R290 are common candidates. The correct choice depends on capacity, source temperature, process temperature, safety infrastructure, and site expertise.

Are fluorinated heat pumps already prohibited?

There is no immediate blanket ban on every fluorinated heat pump. Regulation (EU) 2024/573 introduces different placing-on-market dates according to equipment category, capacity, architecture, GWP, and safety conditions.

Can an R290 heat pump work in a cold climate?

Yes, when the product is designed for the local climate. Check output, COP, operating limit, defrost strategy, backup heat, and sound at the actual winter design temperature.

Does an R290 monoblock contain refrigerant inside the building?

An outdoor monoblock normally keeps the refrigerant circuit in the outdoor unit. Heating water enters the building. Exact architecture and safety requirements must be confirmed from the product documentation.

Do natural-refrigerant heat pumps require maintenance?

Yes. The heat pump still contains compressors, pumps, valves, heat exchangers, controls, filters, water circuits, safety devices, and electrical equipment. Maintenance requirements depend on the product and installation.