Refrigerants in Heat Pumps

A refrigerant is the working fluid inside a heat pump’s sealed refrigerant circuit. It absorbs heat from air, ground, water, or waste heat at a low temperature. The compressor raises the refrigerant’s pressure and temperature. The refrigerant can then release useful heat to a building, domestic hot-water system, or industrial process.

The refrigerant is not a fuel. It is also not the same as the brine in a ground-source collector or the heating water in radiators and underfloor heating. A correctly operating heat pump circulates the same refrigerant repeatedly in a closed cycle.

Refrigerant selection takes place as part of the complete heat pump design. The refrigerant, compressor, heat exchangers, valves, controls, lubricants, pipework, charge quantity, and safety measures must work as one system. Refrigerant handling, charging, recovery, and conversion should only follow the manufacturer’s instructions and the applicable qualification requirements.

What is a refrigerant in a heat pump?

A refrigerant is a substance with controlled pressure and phase-change properties. It can evaporate at a low temperature and condense at a higher temperature. These properties allow a heat pump to move thermal energy from a colder source to a warmer heating system.

Most building heat pumps use a vapour-compression cycle. The refrigerant changes between liquid and vapour as it passes through the system. The compressor provides the electrical work needed to raise the refrigerant’s pressure and temperature.

Refrigerant compared with other heat pump fluids

What is the core purpose of a refrigerant?

The core purpose of the refrigerant is to transfer heat across a temperature difference. The heat source may be cold compared with the required room-heating or hot-water temperature. The refrigerant makes this transfer possible by changing pressure, temperature, and physical state.

The refrigerant does not create the environmental heat. It collects and carries that heat. The compressor then enables the heat to be delivered at a more useful temperature.

How the refrigerant cycle works

Step 1: Evaporation

The low-pressure refrigerant enters the evaporator. It absorbs heat from outdoor air, ground-source brine, groundwater, or another heat source. This heat causes the refrigerant to evaporate.

Step 2: Compression

The compressor draws in the refrigerant vapour. It compresses the vapour to a higher pressure. The refrigerant temperature rises as a result.

Step 3: Condensation

The hot refrigerant passes through the condenser. It releases heat to the heating water or another heat sink. The refrigerant changes back into a liquid as it releases heat.

Step 4: Expansion

The liquid refrigerant passes through an expansion valve. The valve reduces its pressure and temperature. The refrigerant can then enter the evaporator and repeat the cycle.

A reversible heat pump can also provide active cooling. In cooling mode, the system changes the direction of heat transfer. It collects heat from the building and releases it to the outside air, ground, or water source.

Why are refrigerants needed?

A building may require heating water at 30°C, 45°C, 55°C, or more. The available heat source may be much colder. Outdoor air can be below freezing, while ground or groundwater temperatures remain relatively low.

The refrigerant provides a practical way to bridge this temperature difference. It can evaporate below the source temperature and condense above the required heating-water temperature. The compressor moves the refrigerant between these operating conditions.

Without a suitable refrigerant and refrigerant circuit, a compression heat pump cannot transfer low-temperature environmental heat into a useful heating system.

The practical need for correct refrigerant selection

Incorrect system selection can create real operating and business problems:

• The heat pump may not deliver the required heating output on the coldest design day.
• The unit may need excessive compressor power at high flow temperatures.
• The available installation area may not meet the required safety distances.
• A split system may introduce unnecessary on-site refrigerant connections.
• A high-GWP refrigerant may create regulatory, supply, and lifecycle risks.
• An uncommon refrigerant may have limited local service support.
• A large refrigerant charge may increase direct emission consequences.
• A poor match between refrigerant and compressor may reduce efficiency or component life.
• An unapproved refrigerant conversion may damage the compressor, seals, lubricant, or heat exchangers.

The German Environment Agency states that there is no single perfect refrigerant for every application. The correct choice depends on the specific system, operating conditions, construction requirements, energy use, environmental impact, availability, and legal framework.

Key features of heat pump refrigerants

A refrigerant must be assessed through several connected properties. No single value provides a complete evaluation.

Detailed explanation of refrigerant features

Phase-change behaviour

Definition: Phase-change behaviour describes how a refrigerant changes between liquid and vapour.

Purpose: The phase change allows the fluid to absorb or release a large amount of heat within a compact circuit.

Benefit: The heat pump can transfer substantial thermal energy without circulating an extremely large fluid volume.

Example: The refrigerant evaporates in the outdoor unit of an air-source heat pump and condenses while heating the building water.

Pressure-temperature relationship

Definition: Each refrigerant has a specific relationship between saturation pressure and temperature.

Purpose: This relationship allows engineers to create a low-temperature evaporation condition and a higher-temperature condensation condition.

Benefit: The heat pump can operate between the available source temperature and the required heating-water temperature.

Example: On a cold winter day, the refrigerant must evaporate below the outdoor-coil temperature while condensing above the required flow temperature.

Operating envelope

Definition: The operating envelope defines the permitted source temperatures, condensing temperatures, pressures, and compressor conditions.

Purpose: It prevents operation outside the limits of the refrigerant, compressor, lubricant, motor, and other components.

Benefit: Correct operation protects efficiency and equipment life.

Example: A renovation project should verify heating capacity and compressor limits at the actual winter design temperature and required radiator flow temperature.

Critical temperature and high-temperature capability

Definition: Critical temperature is the temperature above which a fluid no longer has a normal liquid-vapour phase boundary.

Purpose: It helps determine how a refrigerant behaves at high heat-sink temperatures.

Benefit: It supports the selection of systems for domestic hot water, radiators, process heat, or district heating.

Example: A heat pump designed for a 70°C flow temperature needs a refrigerant circuit, compressor, and controls that are validated for that complete operating condition.

A high theoretical temperature capability does not guarantee efficient operation. Compressor discharge temperature, pressure ratio, heat-exchanger approach temperatures, source temperature, and control strategy remain important. Product data at defined test conditions provides more useful evidence than the refrigerant name alone.

Thermodynamic efficiency

Definition: Thermodynamic properties describe how the refrigerant stores, transports, absorbs, and releases energy.

Purpose: They help the system achieve useful heating output with limited compressor work.

Benefit: A suitable fluid can support good coefficient of performance and seasonal efficiency.

Example: A refrigerant may perform well in a purpose-designed system but poorly if used in components designed for another fluid.

Efficiency is a system result. The refrigerant influences efficiency, but it does not determine efficiency alone. Compressor modulation, fan and pump power, heat-exchanger size, defrost control, source temperature, flow temperature, hydraulic design, and installation quality also matter.

Volumetric heating capacity

Definition: Volumetric capacity describes how much heating or cooling capacity a refrigerant can provide for a given vapour volume.

Purpose: It helps engineers size the compressor, pipework, valves, and heat exchangers.

Benefit: A suitable volumetric capacity can support compact equipment and stable control.

Example: Two refrigerants may deliver similar heating output but require different compressor displacement and circuit dimensions.

Safety classification

Definition: Refrigerant safety classes describe toxicity and flammability.

Purpose: They create a common basis for product design, charge limits, room requirements, ventilation, ignition-source control, installation, and servicing.

Benefit: The correct safety concept allows refrigerants with different properties to be used responsibly.

Example: R744 is classified A1, R32 is A2L, R290 is A3, and R717 is B2L in current reference tables.

The letter describes toxicity classification:

• A: lower toxicity
• B: higher toxicity

The number describes flammability:

• 1: no flame propagation under the defined test conditions
• 2L: lower flammability with low burning velocity
• 2: flammable
• 3: higher flammability

A safety class is not a complete risk assessment. A1 does not mean that every installation is automatically safe. A3 does not mean that the refrigerant cannot be used safely. Equipment construction, charge, installation location, ventilation, detection, service procedures, and applicable standards control the practical risk.

Global warming potential

Definition: Global warming potential, or GWP, compares the warming effect of a gas with the effect of carbon dioxide over a defined period, usually 100 years.

Purpose: It provides a common way to estimate the direct climate effect of a refrigerant release.

Benefit: It allows refrigerants and charge quantities to be compared in carbon-dioxide equivalents.

Example: Releasing 1 kg of a refrigerant with a GWP of 675 represents 675 kg CO₂ equivalent.

The basic calculation is:

Direct refrigerant impact in kg CO₂e = refrigerant mass released in kg × GWP100

Examples based on current regulatory values include:

• 1 kg R410A released: approximately 2,088 kg CO₂e
• 1 kg R32 released: 675 kg CO₂e
• 1 kg R454C released: 146 kg CO₂e
• 1 kg R744 released: 1 kg CO₂e
• 1 kg R290 released: approximately 0.02 kg CO₂e under the current European Commission calculation basis

Many older technical documents state a GWP of 3 for R290. The European Commission’s current alternatives tables use 0.02 under the calculation basis referenced by Regulation (EU) 2024/573. Values should therefore be compared using the same assessment and regulatory basis.

Direct and indirect climate effects

Definition: Direct effects result from refrigerant emissions, while indirect effects result mainly from the electricity used by the heat pump.

Purpose: Considering both effects prevents an incomplete environmental comparison.

Benefit: Project teams can reduce refrigerant emissions without ignoring seasonal energy use.

Example: A very low-GWP system can still perform poorly if it is oversized, operates at unnecessarily high flow temperatures, or has an inefficient hydraulic design.

The lowest GWP does not automatically create the lowest total environmental impact. The system should combine:

• Low direct refrigerant emissions
• Low or ultra-low refrigerant GWP
• High seasonal efficiency
• Low auxiliary energy use
• Correct sizing
• Low required flow temperatures
• Tight construction
• Professional installation
• Controlled recovery at end of life

Ozone depletion potential

Definition: Ozone depletion potential, or ODP, describes a substance’s potential effect on the stratospheric ozone layer.

Purpose: It distinguishes ozone-depleting refrigerants from alternatives with zero ODP.

Benefit: It supports compliance with international and European ozone-protection rules.

Example: Older CFC and HCFC refrigerants were restricted or phased out because of their ozone impact.

ODP and GWP measure different environmental effects. A refrigerant can have zero ODP and still have a high GWP. Both values must therefore be assessed separately.

Temperature glide

Definition: Temperature glide occurs when some refrigerant blends evaporate or condense across a temperature range rather than at one constant saturation temperature.

Purpose: The glide can be matched to the changing temperature of water or air in a heat exchanger.

Benefit: A purpose-designed circuit may use the temperature profile effectively.

Example: A heat pump using an HFC/HFO blend must use heat exchangers, controls, charging procedures, and service methods designed for that blend.

Temperature glide can also complicate diagnostics and charging. Leakage can change the composition of some blends. Service personnel must follow the product manufacturer’s specified procedure.

Material and lubricant compatibility

Definition: Compatibility describes how the refrigerant interacts with compressor oil, metals, elastomers, plastics, seals, valves, and motor insulation.

Purpose: It prevents chemical breakdown, poor lubrication, seal failure, and component damage.

Benefit: Correct compatibility supports stable operation and a long service life.

Example: An R410A system cannot be assumed to accept R32, R290, or another refrigerant without a manufacturer-approved conversion design.

A refrigerant is not a simple interchangeable consumable. Pressure levels, oil behaviour, motor cooling, expansion devices, heat exchangers, safety controls, and certification may all change. The German Environment Agency warns that an unprofessional conversion can damage the system and create high costs.

Refrigerant charge

Definition: Refrigerant charge is the mass of refrigerant contained in the equipment.

Purpose: The charge provides the correct refrigerant distribution through the evaporator, compressor, condenser, receiver, and connecting pipework.

Benefit: An optimised charge supports performance while limiting safety and environmental consequences.

Example: A factory-sealed monoblock can contain the refrigerant circuit within the manufactured outdoor unit, while a split system usually requires refrigerant pipe connections on site.

Too little refrigerant can reduce capacity and cause unstable operation. Too much refrigerant can raise pressure and impair heat-exchanger performance. Charge quantity should only be changed according to the manufacturer’s data and service procedure.

Tightness and leakage control

Definition: Tightness describes the ability of the refrigerant circuit to retain its charge throughout operation and servicing.

Purpose: It protects performance, safety, and the environment.

Benefit: A tight circuit reduces service calls, refrigerant loss, direct emissions, and downtime.

Example: Factory-made joints can reduce the number of site-made refrigerant connections, although every system still requires correct installation and inspection.

A refrigerant should not need routine “topping up” in a correctly functioning sealed system. Refrigerant loss indicates a leak or an incomplete service procedure. The cause should be found and repaired before the charge is restored.

Regulatory and service availability

Definition: Regulatory availability describes whether equipment and refrigerant can continue to be placed on the market, serviced, recovered, and supported.

Purpose: It connects technical selection with the expected life of the asset.

Benefit: A durable choice lowers procurement, supply, compliance, and downtime risks.

Example: An EU heat pump project with a 15- to 25-year operating horizon should account for the F-gas equipment restrictions, HFC quota reduction, technician qualifications, and local service capacity.

Types of refrigerants used in heat pumps

Heat pump refrigerants can be grouped by chemical family. The main groups are natural refrigerants, HFCs, HFOs, and HFC/HFO blends. Each group contains fluids with different pressures, safety classes, operating properties, and regulatory positions.

Natural refrigerants

Definition: Natural refrigerants are substances that occur in natural material cycles and are used as working fluids.

Purpose: They provide alternatives to fluorinated greenhouse gases.

Benefit: Many have zero or ultra-low GWP and are not subject to the EU HFC quota.

Example: Common heat pump refrigerants include propane R290, carbon dioxide R744, and ammonia R717.

The term “natural” does not mean risk-free. R290 is flammable. R717 has a higher-toxicity classification. R744 operates at high pressure and requires a circuit designed for its particular thermodynamic behaviour.

Hydrofluorocarbons

Definition: Hydrofluorocarbons, or HFCs, are fluorinated substances that contain hydrogen, fluorine, and carbon.

Purpose: They replaced many ozone-depleting refrigerants in refrigeration, air-conditioning, and heat pump systems.

Benefit: HFCs offered useful thermodynamic properties and several established safety classifications.

Example: R32 and the R410A blend are widely recognised HFC-based refrigerants.

HFCs generally have zero ozone depletion potential. Their GWP can still be significant. They are subject to the EU F-gas quota and increasingly strict equipment rules.

Hydrofluoroolefins

Definition: Hydrofluoroolefin, or HFO, is an industry term commonly used for unsaturated fluorinated refrigerants.

Purpose: HFOs were developed to provide lower-GWP alternatives for specific applications.

Benefit: Several have much lower GWP values than traditional HFCs.

Example: R1234ze(E), R1233zd(E), and R1336mzz(Z) appear in chiller and high-temperature applications.

HFO suitability depends on safety class, operating temperature, materials, degradation products, product availability, and regulation. Low GWP should not be treated as the only environmental criterion.

HFC/HFO blends

Definition: HFC/HFO blends combine two or more refrigerant components.

Purpose: Manufacturers use blends to balance GWP, capacity, pressure, safety class, and operating performance.

Benefit: A blend may support equipment transitions without requiring the same architecture as a natural refrigerant system.

Example: R454B, R454C, and R513A are blends considered for different heat pump and chiller applications.

Blends can have temperature glide. They may also remain subject to F-gas rules even when their GWP is below older refrigerants. Their long-term position depends on product category and applicable GWP thresholds.

Comparison of common heat pump refrigerants

Fluorinated refrigerants, PFAS, and TFA

Some fluorinated refrigerants fall within broad PFAS definitions or can form persistent trifluoroacetic acid, known as TFA, during atmospheric degradation. This issue is separate from GWP and ozone depletion. It is increasingly relevant to long-term environmental and procurement assessments.

As of July 2026, the proposed broad EU restriction of PFAS was still moving through the REACH decision process. ECHA’s Risk Assessment Committee had adopted its opinion, while the Socio-Economic Analysis Committee was expected to complete its final opinion by the end of 2026. This was not yet a general EU ban on all fluorinated refrigerants.

Project teams should therefore avoid two extremes. They should not ignore PFAS and TFA considerations. They should also not describe a proposed restriction as an already applicable blanket refrigerant ban.

Refrigerant use cases

The application defines the operating conditions. The same refrigerant choice may not be optimal for a low-temperature new building, a radiator renovation, a hotel, and an industrial process.

Benefits of choosing the correct refrigerant system

Correct refrigerant selection improves more than one technical metric. It aligns the product with the building, heat source, temperature requirement, installation site, service network, and regulatory horizon.

The main benefits include:

• Reliable output: The heat pump can meet the design heating load.
• Efficient operation: The compressor works within an appropriate pressure and temperature range.
• Lower direct climate risk: Low-GWP refrigerants reduce the impact of a possible release.
• Lower indirect emissions: Good seasonal efficiency reduces electricity demand.
• Safe installation: The safety class is matched with the charge, product construction, and site.
• Regulatory durability: The product is less exposed to future market restrictions.
• Serviceability: Qualified technicians, components, and approved service procedures are available.
• Longer system life: Compatible materials, lubricants, and controls protect the equipment.
• Lower downtime risk: The system can be maintained without relying on scarce refrigerant or skills.
• Better project economics: Performance, compliance, maintenance, and replacement risks are considered before purchase.
• Clearer environmental reporting: Refrigerant type, charge, GWP, and CO₂-equivalent content can be documented.
• Controlled end of life: Refrigerant can be recovered, recycled, reclaimed, or destroyed through the correct process.

Natural refrigerants can provide very low direct climate impact when the equipment is specifically designed for them. The German Environment Agency also stresses that their flammability, toxicity, or pressure properties must be managed through appropriate standards and system design.

How to select a heat pump refrigerant

Do not begin by asking, “Which refrigerant is best?” Begin by defining the application. Then select a complete heat pump that performs safely and efficiently under those conditions.

Step 1: Define the heating and cooling loads

Calculate the building’s design heating load. Identify peak hot-water demand and any cooling load. Separate continuous loads from short peak loads.

Required data includes:

• Heated floor area
• Building envelope quality
• Local winter design temperature
• Internal and solar gains
• Domestic hot-water profile
• Ventilation losses
• Cooling requirements
• Planned extensions or process loads

Step 2: Define the heat source

Identify whether the system uses outdoor air, ground, groundwater, surface water, exhaust air, wastewater, or process waste heat. Record the expected minimum and maximum source temperatures. Confirm permits and source-side pumping requirements.

The source temperature directly affects refrigerant evaporation temperature. A colder source increases the required temperature lift. This normally reduces efficiency and available heating capacity.

Step 3: Define the heat-sink temperature

Determine the actual heating-water flow and return temperatures. Do not use the boiler’s previous setpoint without checking the emitters and building load. Oversized radiators, hydraulic balancing, insulation measures, and lower system temperatures can improve heat pump performance.

Check:

• Underfloor-heating design temperature
• Radiator output at reduced temperatures
• Domestic hot-water target
• Legionella-control strategy
• Process-temperature requirement
• Summer cooling-water temperature

Step 4: Verify performance at the design point

Compare heat pumps at the same source and sink conditions. Review declared heating capacity, compressor input, coefficient of performance, backup-heater use, and operating limits. Seasonal labels alone cannot replace a project-specific winter check.

For an air-source unit, relevant questions include:

• What output remains at the local design temperature?
• At what flow temperature is that output stated?
• Does the compressor remain inside its permitted envelope?
• When does the electric backup heater operate?
• How is defrost included?
• What is the sound output at high load?

Step 5: Choose the system architecture

Decide whether a monoblock, split, indoor, outdoor, or modular system is appropriate. The architecture determines where the refrigerant is located and whether site-made refrigerant joints are required.

Consider:

• Space inside and outside the building
• Distance to property boundaries
• Access for service
• Hydraulic frost protection
• Refrigerant pipe length
• Number of joints
• Water and refrigerant exposure inside occupied spaces
• Future expansion
• Redundancy requirements

Step 6: Assess refrigerant safety

Identify the ISO 817 safety class. Review charge quantity, installation location, room size, ventilation, drainage, ignition sources, protected zones, and service access. Apply the current product and installation standards.

Safety assessment should cover normal operation and foreseeable faults. It should also cover transport, commissioning, maintenance, leak response, and decommissioning.

Step 7: Compare environmental performance

Record the refrigerant type, charge, and GWP. Calculate the total CO₂-equivalent content. Then compare the product’s seasonal energy performance.

A useful assessment includes:

• Refrigerant GWP
• Refrigerant charge
• Expected leakage risk
• Factory sealing
• Number of on-site joints
• Seasonal efficiency
• Electricity source
• Product life
• Recovery plan
• Recycled or reclaimed refrigerant options where relevant
• PFAS or degradation-product considerations

Step 8: Check the regulatory horizon

Confirm the product category, rated capacity, system type, refrigerant family, GWP, and planned market date. Compare these details with current EU or Swiss rules. Do not rely on a general statement that a refrigerant is “approved” or “future-proof.”

A substance may remain legally available while a specific equipment category becomes restricted. New-equipment rules, servicing rules, quota rules, leak-control duties, and national safety rules are separate requirements.

Step 9: Check service and supply capacity

Confirm that local technicians are trained for the refrigerant and product. Check access to spare parts, recovery equipment, diagnostic tools, and approved lubricants. Ask how the manufacturer supports the product over its expected operating life.

Step 10: Verify end-of-life responsibilities

The procurement plan should include decommissioning. Refrigerant must not be intentionally vented. Recovery, transport, recycling, reclamation, or destruction should be assigned to qualified parties.

Refrigerant procurement checklist

Ask the supplier or system designer:

1. What refrigerant does the exact model use?
2. What is the factory refrigerant charge?
3. What is its GWP and total CO₂-equivalent content?
4. What is its ISO 817 safety class?
5. Is the refrigerant circuit factory sealed?
6. Are refrigerant connections made on site?
7. What source and flow temperatures define the published output?
8. What heating capacity remains at the project design point?
9. What is the maximum permitted flow temperature?
10. What safety distances or protected areas are required?
11. Which standards and national rules apply?
12. Which technician qualification is required?
13. Are local service partners trained for the refrigerant?
14. What leak-detection or inspection duties apply?
15. How is the refrigerant recovered at end of life?
16. Is an alternative refrigerant conversion permitted in writing?
17. Which future EU or Swiss market restrictions affect the product category?
18. What product documentation records the refrigerant, charge, and safety information?

EU refrigerant rules for Austria, Germany, and Italy

Austria, Germany, and Italy apply Regulation (EU) 2024/573 on fluorinated greenhouse gases. The regulation has applied since 11 March 2024. It includes HFC quota reductions, equipment prohibitions, leak prevention, certification, labelling, recovery, reporting, and servicing requirements. The European Commission states that HFCs in the EU quota system are scheduled to be phased out by 2050.

Important EU placing-on-the-market dates

The following dates mainly concern new equipment placed on the EU market. They do not mean that every existing installed heat pump must stop operating on that date. Servicing and use restrictions are governed separately.

EU operating and servicing obligations

The F-gas Regulation also requires lifecycle control:

• Operators and manufacturers must take feasible measures to prevent and minimise F-gas leakage.
• Detected leaks must be repaired without undue delay.
• Installation, maintenance, repair, decommissioning, leak checks, and recovery require the applicable certification or training.
• The revised qualification framework also addresses relevant alternatives, including natural refrigerants.
• F-gas heat pumps must carry defined refrigerant and charge information.
• Refrigerant must be recovered during decommissioning and then recycled, reclaimed, or destroyed.
• Records for equipment subject to leak checks must generally be retained for at least five years.

Periodic leak checks can apply from 5 tonnes CO₂ equivalent for Annex I gases or from 1 kg for specified Annex II gases. Hermetically sealed equipment has defined exemptions, including a residential exemption below 3 kg where the equipment is correctly labelled. Check frequency increases with refrigerant quantity, while qualifying leak-detection systems can extend the interval.

From 1 January 2026, F-gases with GWP of 2,500 or more are restricted for servicing air-conditioning equipment and heat pumps. Reclaimed and defined recycled gases have transitional exceptions until 1 January 2032. R410A, with a GWP of 2,088, is below this specific 2,500 service threshold, but it remains affected by HFC quota reduction and wider new-equipment policy.

Refrigerant rules in Switzerland

Switzerland does not apply the EU F-gas Regulation directly. Refrigerants are regulated under Annex 2.10 of the Swiss Chemical Risk Reduction Ordinance, known as ChemRRV. The rules aim to reduce emissions from ozone-depleting and strongly climate-warming refrigerants.

The Swiss Federal Office for the Environment has published revised requirements applying from 1 January 2027. Swiss projects must use the current BAFU guidance for the exact plant type, capacity, refrigerant, charge, and placing-on-the-market date.

Swiss obligations can include:

• Restrictions on equipment using stable-in-air refrigerants
• Leak checks
• A maintenance log
• Installation reporting
• Refrigerant documentation
• Qualified handling and disposal

People who professionally install, maintain, manufacture, or dispose of heat pump and refrigeration equipment require the applicable Swiss specialist authorisation or recognised equivalent qualification.

Relevant refrigerant safety standards

Regulations define legal obligations. Standards provide detailed engineering methods for refrigerant classification, product construction, charge limits, installation, operation, maintenance, and recovery. The applicable edition and national adoption should be checked for the project date.

ISO 817

ISO 817 provides refrigerant designations, safety classifications, toxicity and flammability categories, and refrigerant concentration-limit data. It creates the common language behind classes such as A1, A2L, A3, and B2L.

EN 378

EN 378 covers safety and environmental requirements for refrigeration systems and heat pumps. It addresses classification, selection, design, location, operation, maintenance, repair, and refrigerant recovery. Austria publishes the national ÖNORM EN version, while the corresponding national editions apply in other markets.

IEC 60335-2-40

IEC 60335-2-40 covers product safety requirements for electrical heat pumps, air conditioners, and dehumidifiers for household and similar applications. It includes requirements connected with refrigerant circuits and product construction.

Standards should not be reduced to a single safety distance. The applicable requirements can depend on refrigerant class, charge, installation height, room size, appliance construction, ventilation, detection, and product-specific protective measures.

Refrigerant comparisons

Natural refrigerants compared with fluorinated refrigerants

R290 compared with R32

The comparison should still be made at product level. An R290 label does not establish heating capacity, sound output, seasonal efficiency, minimum modulation, service quality, or hydraulic suitability. The same rule applies to R32.

Monoblock compared with split heat pumps

Low GWP compared with high efficiency

Low GWP and high efficiency should not be treated as competing goals. A responsible system should minimise both direct and indirect emissions. Refrigerant GWP addresses the effect of a release, while seasonal efficiency addresses electricity use.

Select using this sequence:

1. Confirm that the product can safely serve the application.
2. Confirm capacity at the actual design conditions.
3. Compare seasonal and design-point efficiency.
4. Compare refrigerant charge and GWP.
5. Assess leakage risk and installation architecture.
6. Check the electricity source.
7. Confirm service and recovery arrangements.
8. Check the full regulatory horizon.

Integration with other heat pump systems

The refrigerant circuit is one part of a larger energy system. Good integration allows the heat pump to operate with lower temperatures, longer cycles, lower auxiliary energy, and fewer operating interruptions.

Integration with the heat source

Definition: The heat-source system supplies energy from air, ground, water, wastewater, exhaust air, or waste heat.

Purpose: It maintains the source conditions needed for stable refrigerant evaporation.

Benefit: A well-designed source reduces compressor pressure ratio and supports efficiency.

Example: A ground-source heat pump uses a separate brine or groundwater circuit to transfer heat to the refrigerant evaporator.

For air-source systems, fan control, coil design, condensate drainage, icing, and defrost are important. For ground-source systems, borehole or collector sizing, brine concentration, flow rate, and source-pump power matter. The refrigerant cannot correct an undersized heat source.

Integration with heating-water distribution

Definition: The heating-water system distributes condenser heat through underfloor heating, radiators, fan coils, or air-handling units.

Purpose: It delivers the heat produced by the refrigerant cycle to occupied spaces.

Benefit: Low and stable flow temperatures reduce the required temperature lift.

Example: Hydraulic balancing and appropriately sized radiators can lower the flow temperature in a renovation.

The refrigerant and heating water remain separated by the condenser. Poor water flow, blocked filters, air in the circuit, or incorrect pump control can raise condensing pressure. This can reduce efficiency and trigger faults.

Integration with domestic hot water

Definition: Domestic hot-water integration transfers heat from the refrigerant circuit into a cylinder or fresh-water module.

Purpose: It provides hot water for showers, sinks, kitchens, and other uses.

Benefit: One system can cover room heating and domestic hot water.

Example: The control system can temporarily prioritise cylinder charging before returning to space heating.

Hot-water operation usually requires a higher refrigerant condensing temperature than floor heating. Storage volume, heat-exchanger area, target temperature, recirculation losses, hygiene control, and user profile affect performance.

Integration with cooling

Definition: Cooling integration removes heat from the building through active or passive cooling.

Purpose: It maintains indoor comfort during warm periods.

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

Example: A reversible air-source heat pump can actively reverse the refrigerant cycle, while a ground-source system may also offer passive cooling without compressor operation.

Cooling requires condensation control. Water temperatures must remain above the surface dew point unless the emitters and drainage system are designed for condensation. Room controls, humidity monitoring, and hydraulic separation may be needed.

Integration with buffer and storage systems

Definition: A buffer or thermal store separates energy production from short-term demand.

Purpose: It can provide hydraulic stability, defrost energy, load shifting, or separation between circuits.

Benefit: Correct storage can reduce cycling and support several temperature zones.

Example: A commercial system may use storage to coordinate space heating, domestic hot water, and peak-load management.

Storage should not be added without a defined purpose. An oversized or poorly connected buffer can increase standing losses and operating temperature. The hydraulic concept should preserve low return temperatures and stable volume flow.

Integration with photovoltaic systems and energy management

Definition: Energy management coordinates the heat pump with photovoltaic generation, electricity tariffs, batteries, storage, and building demand.

Purpose: It moves flexible heat production into favourable operating periods.

Benefit: It can increase self-consumption and reduce electricity cost without compromising comfort.

Example: The controller can raise a storage target within safe limits when excess photovoltaic electricity is available.

The control strategy should not force inefficient high temperatures merely to consume electricity. Building thermal mass, domestic hot-water demand, weather forecasts, tariff periods, and compressor operating limits should be considered together.

Integration with cascades and large systems

Definition: A cascade combines two or more heat pump modules.

Purpose: It increases capacity, modulation range, and redundancy.

Benefit: The system can match variable commercial or multifamily loads while retaining partial operation during maintenance.

Example: The controller stages modules according to current load and operating hours.

Cascade design must coordinate flow, return temperature, storage, source capacity, electrical connection, controls, acoustic output, service access, and simultaneous defrost. Multiple modules do not correct an undersized source or poorly designed hydraulic system.

Refrigerants within the iDM energy-system approach

iDM Energiesysteme GmbH positions the refrigerant as one element of a complete heating, cooling, hot-water, control, and energy-management solution. Product selection should therefore begin with the heat source, building load, required flow temperature, hydraulic system, installation location, and control strategy.

Current iDM product information includes several systems using R290 or another natural refrigerant:

These product examples show why refrigerant selection cannot be separated from product architecture. The iPUMP A ONE combines an R290 circuit with an integrated hot-water concept. The iPUMP T7 ONE applies R290 to ground or groundwater sources. The AERO ALM MAX combines a natural refrigerant with modular capacity, separate circuits, and energy-management integration.

The exact refrigerant, charge, output, operating limits, and country-specific product configuration should always be checked in the current technical documentation for the selected model.

Frequently asked questions about heat pump refrigerants

Is refrigerant consumed during normal heat pump operation?

No. The refrigerant circulates repeatedly in a closed circuit. A falling charge normally indicates leakage, incomplete commissioning, or a service issue.

Does a heat pump need regular refrigerant refilling?

A correctly sealed system should not need routine refilling. Adding refrigerant without finding the cause of the loss can hide a leak. The system should be tested, repaired, evacuated where required, and charged according to the manufacturer’s procedure.

Which refrigerant is best for a heat pump?

There is no universally best refrigerant. The optimum choice depends on heat source, heating-water temperature, capacity, product architecture, installation site, safety, efficiency, environmental impact, regulation, and service availability.

Is R290 safe in a heat pump?

R290 is classified A3 because it is flammable. Purpose-designed heat pumps manage this property through charge control, sealed construction, component placement, ventilation or outdoor installation, ignition-source management, and defined site requirements. The complete certified product and installation concept determines safety.

Is R32 banned?

R32 is not subject to one immediate blanket ban across all existing heat pumps. It has a GWP of 675 and is affected by the EU HFC quota and by future equipment prohibitions that depend on capacity and system category. For example, new split air-to-water systems up to 12 kW using F-gases with GWP of 150 or more are restricted from 1 January 2027, subject to defined safety exceptions.

Is R410A banned?

Existing R410A equipment is not automatically required to stop operating. R410A has a GWP of 2,088, so it faces strong quota and new-equipment pressure. It is below the specific GWP 2,500 service restriction that began on 1 January 2026, but refrigerant availability and cost can still be affected by the wider HFC phase-out.

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

Not without an approved engineering solution from the manufacturer. The refrigerants use different pressures, oils, safety measures, compressors, valves, controls, and charge requirements. An unapproved conversion can damage the heat pump and invalidate its conformity or warranty.

Does low GWP mean high efficiency?

No. GWP describes the climate effect of a release. Efficiency describes the useful heat delivered relative to energy input. A good heat pump should combine low direct refrigerant impact with high seasonal efficiency.

What is the difference between refrigerant and brine?

Refrigerant circulates inside the heat pump’s sealed compression circuit. Brine circulates through a ground collector or borehole and transfers source heat to the evaporator. A heat exchanger separates the two fluids.

What is the difference between refrigerant and heating water?

Refrigerant transfers heat inside the heat pump. Heating water distributes the released heat through radiators, underfloor heating, fan coils, or storage. The condenser separates the refrigerant from the water circuit.

What does refrigerant charge mean?

Charge means the mass of refrigerant contained in the equipment. It is normally stated in kilograms. For F-gases, documentation may also state the charge in tonnes of CO₂ equivalent.

What happens to the refrigerant when a heat pump is replaced?

The refrigerant should be recovered by an appropriately qualified person. F-gases must then be recycled, reclaimed, or destroyed according to the applicable rules. They must not be intentionally released to the atmosphere.

Are natural refrigerants always non-toxic and non-flammable?

No. R290 is flammable. R717 has a higher-toxicity classification. R744 is non-flammable but operates at high pressure. “Natural” describes the refrigerant family and environmental context, not the absence of engineering risks.

Are HFO refrigerants free from environmental concerns?

Not necessarily. Several HFOs have very low GWP, but broader questions can include atmospheric degradation products, PFAS definitions, production impacts, and future chemicals regulation. These factors should be assessed together with energy efficiency, safety, charge, and application suitability.