MACS 609 Certification Practice Exam

What happens when CFC-12 and HFC-134a are mixed in the same system?

1. They work together effectively

2. Result in refrigerant cross-contamination

3. Enhance cooling efficiency

4. Lead to system freezing

The correct answer is: Result in refrigerant cross-contamination

When CFC-12 and HFC-134a are mixed in the same refrigeration system, the primary concern is refrigerant cross-contamination. CFC-12, a chlorofluorocarbon, and HFC-134a, a hydrofluorocarbon, have different chemical properties and thermodynamic characteristics. Mixing these two refrigerants can disrupt the functioning of the system as each refrigerant operates at different pressure and temperature ranges. The presence of both refrigerants can lead to performance issues such as reduced cooling capacity, inefficient operation, and potential damage to components that are not compatible with both types of refrigerants. Additionally, it complicates the refrigeration cycle, adversely affecting the compressor, expansion valves, and evaporator performance. The system was designed to handle specific types of refrigerants, and mixing them can lead to unpredictable behaviors and inefficiencies. Thus, the outcome of mixing CFC-12 and HFC-134a is indeed refrigerant cross-contamination that negatively impacts the system's operation.