Major refrigerating system safety standards require refrigerant sensors for A2L refrigerants to meet the required response times. IEC 60335-2-40 Edition 6.0 requires the sensor to make an output (meaning triggering the alarm) within 30 seconds when exposed to a refrigerant concentration of 25 % of LFL (lower flammability limit) or lower. The reliability and robustness of refrigerant sensors is being evaluated by AHRI sponsored studies, with Phase I recently published. Six sensors with four different sensing principles (Micro Machined Membrane, Non-Dispersive Infra-Red, Thermal Conductivity and Metal Oxide Semiconductor) were selected for the experimental assessment. Testing included step-change tests and time-varying tests under the typical leakage scenarios. The next two phases of the project will assess and develop test protocols and conduct testing to assess the reliability and robustness of refrigerant sensors.
Explanatory note: HFC-32, some HFC/HFO blends and some HFOs are A2L refrigerants with lower GWPs than the HFCs traditional used, offering a good balance of technical and safety properties and are being increasingly adopted in the EU. There is a relatively wide range of A2L refrigerants, having different components.