R290 leakage hazards assessment of a 1 HP split-type household air conditioner by concentration detection and ignition experiment

• The leak concentration of R290 split-type household air conditioners was measured. • Fire hazards were verified by ignition tests. • A fire occurred under a concentration of 73 % LFL measured by infrared gas detectors. • The low-risk application boundaries of a 1 HP split-type air conditioner were found. • Installing a check valve to decrease the fire hazards was proposed and verified. Propane (R290) is a promising alternative natural refrigerant for refrigeration, air conditioning and heat pump systems to replace hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), but its highly flammable and explosive properties require specific attention and hinder the replacement process. A fire and/or an explosion may occur once R290 leaks. This paper evaluated the fire hazards of a 1 HP split-type household air conditioner (STHAC) with a charge of 260 g to 350 g not only by measuring the R290 concentration distribution 1.5 m above the floor after a leakage occurred in the indoor unit (IDU) under various situations, but also by ignition experiment to examine the validity of concentration distribution results. A new method for reducing fire hazards was provided by installing a check valve near the gas-liquid separator with a solenoid valve installed after the capillary to prevent the transference of refrigerant from the condenser to the evaporator, which was validated to effectively decrease the fire hazards. The effects of charge, leak hole diameter and valve arrangement on the R290 concentration profiles were studied. It was found that under a fast-leaking rate, a fire occurred though the maximal concentration was 73% LFL detected by infrared gas detectors. This indicated that the detected R290 concentration may be lower than the actual concentration at a fast-leaking rate, and the ignition test was probably the most accurate method for fire hazards assessment. The low-risk application boundaries of the 1 HP STHAC were confirmed both by concentration detection and ignition test.