Due to the potential environmental impact, there has been a shift to consider use of natural refrigerants, which have a lower Global Warming Potential (GWP) than traditional fluorocarbon based refrigerants. One type of natural refrigerant are hydrocarbons (e.g. propane), which are classified as Class A3 refrigerants per ASHRAE Standard 34. The Environmental Protection Agency (EPA) has a charge limit of 150g of hydrocarbon per appliance, which is defined as a closed loop refrigeration circuit. Previous work has been completed on Class A2L refrigerants, but Class A3 refrigerants need more study to provide technical basis for any changes to the current limits for use in refrigerator units. There is a need to assess the fire hazard of Class A3 refrigerants, and specifically propane, in larger volumes to evaluate their viability as alternatives to traditional refrigerants in more applications.
Hydrocarbons, including R-290 (propane), are viable refrigerant working fluids with zero ozone depleting potential (ODP) and minimal global warming potential (GWP). The current barrier to more widespread application of hydrocarbons as refrigerants, and A3 refrigerants in general, is their flammability. While fundamental flammability characteristics are well established for most hydrocarbons, there is a need to assess the risks associated with their use as refrigerants and evaluate methods to mitigate such risks, specifically when charge sizes are larger than the currently mandated limits. Further studies are needed to establish a technical basis for any changes to the current charge limits in refrigeration appliances. Furthermore, assessing the risk for larger charge sizes than currently allowed by standards will help determine whether A3 refrigerants can replace hydrofluorocarbons (HFCs) in a broader range of refrigeration and heating, ventilation, and air conditioning (HVAC) applications.
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