CHARACTERIZATION OF NON-DISPERSIVE INFRARED SENSORS FOR R-32 AND R-454B LEAKS

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Date
2022
Authors
Leahy, James Ryan O
Advisor
Sunderland, Peter B
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Abstract
Due to the increased concerns about climate change, multiple states including California havestarted to pass legislation that phases out high global warming potential (GWP) refrigerants in HVAC and refrigeration systems. The likely replacements are A2L refrigerant which have lower GWP and are mildly flammable. This will require area monitoring leak detection systems for all future applications of these refrigerants. These detection systems preferably need to operate continuously for up to 15 years. The UL 60335-2-40 (2019) standard defines the sensor response time which must alarm within 10 seconds of exposure to 100% of the refrigerant’s LFL. Development of sensors capable of meeting the UL 60335-2-40 standard has been slow with many different types of gas sensing technologies being used. One of these technologies that was identified as a potential candidate was non-dispersive infrared (NDIR). A sensor not yet available commercially was able to be obtained to test its response to A2L refrigerants R-32 and R-454B according to the UL 60335-2-40 standard. Three other competing sensing technologies were also obtained to compare the performance of other sensors about to hit the market. These sensors were characterized by their linearity to varying concentrations of A2L refrigerant, response time, and to contamination. All the tested sensors were able to meet the 10 second requirement for response time. However, all but the NDIR sensor experienced a change in output when exposed to a list of prescribed contaminants by the UL 60335-2-40 standard. After the contamination, the NDIR sensor showed no change in its output indicating it experienced no poisoning effect. The NDIR sensor was deemed to have the optimal performance out of the sensing technologies. Long term exposure, exposure to contaminants and refrigerant at the same time, and service lifetime are still concerns.
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