RACA Journal I April 2026 www. refrigerationandaircon. co. za 39
SUPPORT
These include neoprenes, nitrile rubbers, HNBR, PTFE and nylon. Materials that are not compatible and should not be used in hydrocarbon refrigeration systems are EPDM, natural rubbers and silicone rubbers.
While testing has been conducted on a number of selected materials with hydrocarbons it should be noted that there are numerous different grades available in the market, and for this reason, compatibility should be checked with the manufacturer or supplier of the component.
System components Typically, system components used for fluorocarbon refrigerants do not differ significantly when using flammable refrigerants. Component suppliers should be consulted regarding other in-line components such as pressure regulators, solenoid valves and similar.
• Evaporators and condensers: Evaporators and condensers using hydrocarbons tend to be virtually the same design and size as those used for conventional fluorocarbon refrigerants that operate at similar pressures. Heat transfer coefficients tend to be higher for most hydrocarbons but this does not significantly affect heat exchanger dimensions. All common types of heat exchangers are suitable for use with hydrocarbon-based refrigerants.
• Compressors: Most compressor types are suitable for use with hydrocarbon refrigerants, and compressor suppliers should be consulted for application and selection. Using a compressor with flammable refrigerants without the supplier ' s approval may invalidate the warranty. In order to secure satisfactory performance, long life, and to protect the compressor against overload, certain design criteria should be observed. Compressor application notes and data should always be consulted when designing a system. Ensure compressors are clearly labelled to indicate that hydrocarbon refrigerants are being used in the system. The use of crankcase heaters should be considered to avoid excessive oil solubility.
• Refrigerant control devices: All expansion device types are suitable for use with hydrocarbon-based refrigerants, and component suppliers should be consulted for application and selection. Design and selection criteria are the same as those for conventional fluorinated refrigerants. Capillary tube length is specific to each refrigerant. Computer programmes and tables are available for determining capillary tube size and length, although trial and error is generally the preferred route. Thermostatic Expansion
Desiccants
Valves( TEVs) for hydrocarbons are available from control suppliers. Alternatively, TEVs for other refrigerants that operate with similar pressure-temperature relationships can be used. Electronic expansion valves( EEV) may also be used. EEVs used in hydrocarbon systems must conform to the requirements of electrical components.
Desiccants are used within filter dryers. Most commonly used desiccants are compatible with flammable refrigerants.
Pipe size selection When selecting refrigerant line sizes, specific flammable refrigerant pipe sizing literature should be used. Despite most flammable refrigerants having similar operating pressures to the‘ equivalent’ fluorocarbon refrigerants, thermodynamic and transport properties can differ significantly, therefore data for other refrigerants will not be directly applicable. Refrigerant suppliers should provide the appropriate pipe size selection data.
Safe system design and construction All hydrocarbon refrigerants are highly flammable but nontoxic. There are many other safety requirements that should be considered in the design and construction of all refrigerating and air-conditioning installations, regardless of the flammability of the refrigerant used. General safety standards and codes of practice should be consulted for this additional information.
Allowable refrigerant charge The limiting factors associated with the use of hydrocarbon refrigerants are the refrigerant charge size, the occupancy category and the room size.
Clement, I will go into further aspects including the refrigerant charge size, the occupancy category and the room size in the next issue. Flammable refrigerants are being used in more and more applications. It is very important to understand the use of these refrigerants. RACA
REFERENCES:
1. ACRA 2. SANS 10147
Grant Laidlaw
grant @ acra. co. za voices
RACA Journal I April 2026 www. refrigerationandaircon. co. za 39