The most common non-condensable that gets trapped in a refrigeration system is which of the following?

The most common non-condensable gas that gets trapped in a refrigeration system is air. Air can infiltrate the system during maintenance, servicing, or when components are replaced. Once inside the system, air does not condense like refrigerants and can lead to various operational issues, including reduced efficiency and the risk of compressor damage due to excess pressure.

In refrigeration cycles, the presence of non-condensables, especially air, can also raise discharge pressures, leading to higher energy consumption and the potential for overheating. This is why keeping the system free of air and other non-condensable gases is essential for maintaining operational efficiency.