Understanding and Preventing Non-Condensables in Refrigeration Systems

What Are Non-Condensables?
Non-condensables are gases or materials that do not condense into a liquid state under normal refrigeration system conditions. Common examples include air, nitrogen, and moisture. These unwanted substances occupy space within the system, reducing its efficiency and potentially causing damage.

How Non-Condensables Affect Your System
Non-condensables cause significant issues in refrigeration systems, including:

• Increased Head Pressure: Non-condensables take the place of refrigerant vapor, raising system pressure and forcing the compressor to work harder.

• Temperature Imbalances: The presence of non-condensables can cause uneven cooling, reducing system performance.

• Corrosion Risk: Moisture in the system can lead to acid formation, accelerating system wear and potential component failure.

Symptoms of Non-Condensables in the System

• Erratic High-Side Pressure: A high-pressure gauge that fluctuates by 50 psi or more is a common indicator of non-condensables.

• Inefficient Cooling Performance: Reduced system capacity or longer cooling cycles can also point to this issue.

Prevention Steps
Preventing non-condensables from entering the system is crucial for efficient operation and long-term reliability. Follow these best practices to minimize the risk:

1. Proper System Evacuation:

   • Always use a quality vacuum pump and micron gauge to evacuate the system.

   • Pull a vacuum to 500 microns or lower and ensure the system holds this pressure for an extended period. Lower micron readings are even better.

   • Ensure both the high and low sides are open during evacuation to achieve full system evacuation.

2. Use Clean, Dry Refrigerant:

   • Always use fresh refrigerant from a sealed container to avoid contamination.

   • Avoid reusing recovered refrigerant unless it has been properly filtered and tested.

3. Purge Nitrogen After Pressure Testing:

   • If nitrogen is used for leak detection or pressure testing, always purge it completely before charging refrigerant.

4. Use Proper Charging Techniques:

   • When charging a system, use a manifold gauge set with properly functioning valves to minimize air infiltration.

5. Seal Open Lines Promptly:

   • When brazing, purging with nitrogen during the process can help prevent oxidation inside the tubing.

   • Cap open lines immediately after cutting or disconnecting to prevent moisture and air infiltration.

Corrective Action for Non-Condensables
If you suspect non-condensables are present:

• Shutdown the system immediately to avoid excessive pressure damage.

• Re-evacuate the system following proper evacuation procedures.

• Confirm the vacuum holds steady at 500 microns or lower to ensure non-condensables are removed.

By following these preventive steps and understanding the warning signs, you can avoid the costly and damaging effects of non-condensables in your refrigeration systems.