RACA Journal April 2026 RACA_Apr_2026 | Page 40

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The following types of flammable refrigerants are in use: R290 propane, R600a isobutane, R1270 propylene and the A2L refrigerants R32 and 1234yf. A number of other hydrocarbons, such as blends containing ethane, propane or butane, are also used as refrigerants.

Chemical properties The most commonly used hydrocarbons( propane and isobutane) are compatible with standard oils and materials used with HFCs. One exception is propene( propylene), which is not compatible with neoprene. Consequently, special O-rings must be used with this refrigerant.

Efficiency Hydrocarbons have excellent thermodynamic properties, and in this respect, they are as good as or better than HCF or HCFC refrigerants in most applications.

Flammability limits Hydrocarbons are highly flammable and must be handled with care. If they are used responsibly, hydrocarbons can be employed in a variety of refrigeration and air-conditioning applications. In order to ensure safety, applications are governed by various international, regional and national standards and regulations.

Flammable refrigerants can only pose an explosion risk if the concentration is between the lower and upper flammability limits.

When following the safety standards, the concentration of leaked refrigerant will not get above the lower flammability limit where ignition sources can ignite it. The necessary safety precautions and system design depend on the refrigerant charge. Most hydrocarbons are non-toxic, with the main safety risk coming from their flammability, although gaseous hydrocarbons will displace air due to a higher density.

Environmental impact Flammable refrigerants belong to the group of natural refrigerants and have zero ODP and negligible GWP. As a rule, hydrocarbons are by-products from the petrochemical industry.

Pressure and temperature The refrigeration properties of hydrocarbons, such as pressures, pressure ratios and discharge temperatures, are quite similar to those of HCFCs or HFCs in many respects.

Economic aspects The relative cost of a system using hydrocarbons largely depends on the application. In domestic and light commercial applications, the cost of the system is similar to that of systems with HFCs.

Typical applications for hydrocarbons are:

• Domestic refrigerators and freezers

• Bottle coolers

• Ice cream freezers and commercial freezers

• Commercial refrigerators

• Beverage dispensers

• Heat pumps

• Supermarket refrigeration

• Unitary air conditioners

• Chillers( R290)

Lubricants Flammable refrigerants possess full chemical compatibility with nearly all lubricants commonly used within refrigeration systems. Good miscibility is maintained with most lubricants under all operating conditions.

Due to the particularly good solubility with mineral oils, it may be necessary to use a lubricant with lower solubility or increased viscosity to compensate for possible thinning under situations where high solubility could occur. Suppliers should be consulted for properties of oil / refrigerant combinations. Lubricants containing silicone or silicate( often used as anti-foaming additives) are not compatible with hydrocarbon refrigerants and should not be used.

Materials Virtually all common elastomer and plastic refrigeration materials used as O-rings, valve seats, seals and gaskets are compatible with hydrocarbon refrigerants.