Refrigerant leak detection: methods and best practices

Refrigerant leaks are the most common issue in commercial refrigeration. An undetected leak causes capacity loss, excess energy use, and compressor damage.

Signs of a leak

• Capacity loss — the system isn't cooling like it used to
• High superheat — low refrigerant on the return side
• Low subcooling — not enough liquid at the condenser
• Oil traces — oil follows refrigerant out at the leak point
• Abnormal frosting — at the evaporator or expansion valve

Detection methods

1. Electronic detector

The technician's main tool. Sensitive to parts per million (ppm) of refrigerant in the air.

• Pros — fast, accurate, works on all refrigerants
• Cons — sensitive to wind, requires regular calibration
• How to use — slowly sweep all connections, joints, and brazed seams

2. Soapy water

The classic method — apply soapy water to suspect connections and watch for bubbles.

• Pros — simple, cheap, visual
• Cons — only works on accessible leaks that are large enough
• How to use — pinpoint exact location after electronic detection

3. Nitrogen pressure test

Pressurize the circuit with dry nitrogen to test for tightness.

• Pros — full circuit test, detects micro-leaks
• Cons — requires recovering the refrigerant first
• How to use — after a repair or on a new system before charging

4. UV dye

Inject a fluorescent dye into the circuit and inspect with a UV lamp.

• Pros — finds very slow leaks the other methods miss
• Cons — takes time (the dye must circulate), UV lamp required
• How to use — intermittent or very small leaks

Recommended procedure

1. Measure pressures and calculate superheat — confirm the system is short of refrigerant
2. Visual inspection — oil traces, corrosion, vibration
3. Sweep with the electronic detector — all connections systematically
4. Confirm with soapy water — exact location
5. Repair the leak — brazing, component replacement
6. Nitrogen test — confirm tightness after the repair
7. Pull a vacuum — remove moisture and non-condensables
8. Recharge — weigh the exact charge per spec
9. Document — log the amount added in the refrigerant logbook

Legal requirement

In Quebec, the Halocarbons Regulation requires owners of systems containing more than 10 kg of refrigerant to perform an annual leak inspection. Every leak repair and every refrigerant addition must be recorded in the logbook.