What is considered a non-condensable in a refrigeration system?

In a refrigeration system, a non-condensable gas is defined as a substance that does not readily change from a gas to a liquid when cooled or condensed under normal operating conditions. Non-condensables can interfere with the operation and efficiency of the refrigeration cycle.

Air is a mixture primarily consisting of nitrogen and oxygen, which do not condense within the operating temperatures of standard refrigeration systems. As a result, air remains in gaseous form and does not change to a liquid state under the typical conditions encountered in refrigeration processes. This quality makes air a classic example of a non-condensable in a refrigeration system, as its presence can hinder the system's ability to efficiently remove heat.

Meanwhile, substances like carbon dioxide, ammonia, and R-22, while they have varying properties, are designed to condense under refrigeration operation. Therefore, they do not qualify as non-condensable gases because they can change phases from gas to liquid and play critical roles in the refrigeration cycle. Understanding this fundamental distinction helps in the proper operation and troubleshooting of refrigeration systems.