All pressurized HVACR systems can eventually leak refrigerant. Therefore, it's the responsibility of the HVACR technician to monitor systems regularly and inspect for leaks.

Although a tight system — with minimal leakage that doesn't affect system performance — may not pose a problem, a more serious leak will do so, and could occur at any time.

Some leaks are plainly visible to the eye. These include a visible line break, the presence of oil, and quite possibly a refrigerant vapor cloud of escaping gas.

An audible leak might also be detected if a system is pressurized and large leaks are present.

Many Improvements

Leak detection has become greatly enhanced through the use of modern instruments designed to detect very small amounts of refrigerant and leakage.

When a technician has difficulty determining the source of a reduced refrigerant charge, additional detection methods are needed. There are various methods of leak detection, and more than one method may be necessary to conduct a thorough system diagnosis.

When verifying a refrigerant charge, any system appearing low should be suspected of leakage. Topping off the charge is generally acceptable when single (pure) compound refrigerant systems are serviced. However, it isn't acceptable for zeotropic refrigerant blends (blends of two or more components whose equilibrium vapor-phase and liquid-phase compositions are different at given pressures). When vapor leakage occurs, a variation or percentage of the refrigerants in the blended compound is compromised. Recovery of the charge, repair of the system and re-charging with renewed or virgin refrigerant is needed.

The “standing hold” method is often performed on new systems after assembly, but before the final full charging with refrigerant. The Environmental Protection Agency (EPA) allows for a trace amount of R-22 (to about 10 psig) to be added as a detectable gas.

Pressure is increased in the system with dry nitrogen to the low side working maximum pressure (typically 100-150 psig). Pressure is then monitored using a pressure gauge for several hours or longer as needed. If the systems being tested already has been charged, then recovery and evacuation of the refrigerant is done before this test.

Minor changes in temperature generally don't affect the pressure indication of nitrogen, as the same temperature variation would affect a refrigerant pressure-to-temperature relationship. This is a reliable but time consuming method of leak detection. On existing systems, the refrigerant operation must also be shut down during the test. If a leak is detected, it must be found, and often additional methods and tools are needed.

Remember that the service ports can be a leak site. These should be checked after attaching the gauge hoses. Also, remember to check the manifold gauge set for leakage.

The isolation method is used in addition to the standing hold test when areas of the system or tubing can't be accessed. This method requires breaking open the refrigerant piping system (after the charge has first been removed), then re-sealing it and pressure-testing it for leakage.

Bubbling liquid solutions are liquid solutions that bubble up when placed on a leak site. The solution can be applied by spray, dabber, brush, or immersion. A technician can use this method to verify specific leakage points when other methods indicate a general area. The solution can be a messy procedure, and requires time-consuming clean up to remove residue unless the product manufacturer indicates the solution is not damaging or corrosive.

Halide torch method. This method is used for detecting chlorinated refrigerant leaks of one ounce per year or less. Air is drawn over a copper element heated by a hydrocarbon fuel. If halogenated refrigerant vapors are present, the flame changes from a blue color to a bluish green color.

Safety Precaution: With an open flame, additional safety must be considered to prevent property damage, burns, fire, and inhalation hazards. Make sure the area is also absent of combustible mixtures and other flammables.

With the dye injection method, a dye is injected into the refrigerant-charged system. It will seep out of system cracks, and is then usually detectable. A fluorescent type dye, if used, is detectable under ultra-violet light. This also requires access to all areas of the system, as they need to be inspected for dye leakage indicators. The system may also have to operate for several hours before the leak is detected. Determine first if the compressor manufacturer allows dyes to be used on the system during the warranty period, because moisture contamination is possible.

This method requires some time consuming clean up.

Ultra-sonic devices are used to listen for leaks. These will amplify leak noises caused by leaks. Since many ambient noises may be present, there are limitations to using this detector. It's most effective when the surrounding area is very quiet.