Refrigerant Leak Detection of Another Dimension...

You will discover in this page, ways of refrigerant leak detection carried out by certified technicians, as part of air conditioning maintenance.

You’ll love it if you don’t like refrigerant leak in your system. I don’t like refrigerant leak either, so here comes the information.

We wouldn’t want to lose refrigerant due to leaks in the system, and threat the environment using the “Global Warming” banner. Hence refrigerant leak detection is no joke.

Difference between this page, and simple leak detection:

Simple leak detection methods can be carried out at user level. This method do not require external pressurising of the system.

Pressure in from the compressor is enough to detect leaks.

Here is the page.

On the other hand,

This page will talk about extensive leak detection methods, used by technicians to pinpoint leaks, and repair those.

External system pressurising and vacuuming are required for this section.


The methods involved are used together for best air conditioning system leak repair.

In the order of first to last,

  1. pressure test,

  2. halide torch leak detection, or ultrasonic leak detection,

    (followed by leak repair or part replacement – if any)

  3. and finally, vacuum test

Step 1: Pressure test for refrigerant leak detection:

Function of pressure test is to raise the pressure in the system, and detect for pressure drop during holding time.

Pressure drop in the holding test will mean that there is at least one point of leak.

This test is carried out after parts replacement, refrigerant evacuation, or after tube repair.

Steps for pressure test,

  1. evacuate the system from refrigerant before the leak test,

  2. attach the combination gauge set correctly and tightly.

    The compound gauge should be connected to the suction service valve, and the plain gauge should be connected to the liquid line service valve

  3. adjust the knob on the service valves, and regulator on the gauge set, so that test gas can be inserted through the centre manifold of the gauge set

  4. insert Nitrogen gas into the system through the centre manifold and wait until the pressure within the system to reach about 150 psiG (10 barG)

  5. wait for a few hours and monitor the pressure reading on the gauges.

    Please note that the system’s pressure may rise slightly if the test is carried out on mid day, due to temperature rise.

    The inverse may happen when there is temperature drop at night.

    However, this variation will be minimal

  6. waiting time depends on the size of the system.

    Larger systems may require 12 hours of waiting time. Leak detection within smaller system can be achieved in 4 hours

  7. check if there is a constant pressure drop.

    Move to next step if there is any pressure drop.

    Otherwise, release the Nitrogen gas and, move to “Step 3: Vacuum test”

  8. you will be on this step if there is a pressure drop during holding test.

    Next, insert a small amount of R-22 into the system through the centre hose, until the pressure reaches about 150 psiG

Refrigerant leak detection by pressurising

Courtesy for condenser picture: Bryant Air Conditioners

Hang on. What’s next?

We’ll move on to Step 2 of refrigerant leak detection.

Step 2: Refrigerant leak detection through halide torch detector and ultrasonic leak detector:

This step of refrigerant leak detection is important, as Step 1 can’t possibly pinpoint the leak spot.

Halide torch leak detection

Works on the principle of flame colour change in the presence of chlorine based and fluorine based hydrocarbons – our common refrigerant.

A copper plate will be heated by a flame. There will be an open ended hose connection to the flame’s air intake.

Refrigerant leak is detected through change in flame’s colour.

Any colour from bluish-green to purple means that refrigerant leak is present.

The disadvantage of this system is the open flame. However, it is a sensitive tool to detect refrigerant leak.


  1. make sure that the space is ventilated and there are quick escape routes, in case of emergency,

  2. ignite the torch as per manufacturer’s recommendation,

  3. pass the probing hose along tubes and air conditioning parts to detect for leaks,

  4. mark the suspected leaking area for repair or replacement

Refrigerant leak detection using halide torch detector

Ultrasonic leak detection

Detects refrigerant leak by sensing the sound created by vibrating molecules of escaping gas.

The leak might be so small, that it is inaudible to human ears. Hence we need a sensitive noise detection tool for this.

Ultrasonic detectors are equipped with a microphone and signal processor to sense for this sound.

However, the background noise should be very, very low so that results won’t be flawed.

How to detect leaks using this method?

  1. make sure the area is quiet,

  2. switch on the ultrasonic leak detector,

  3. move the probe along your air conditioning system to test for leaks, and mark for repair

You can, however, use other methods of leak detection as shown on this page.

NOTE: Recover the refrigerant and Nitrogen gas into recovery cylinder after completion of a test.

Step 3: Vacuum test:

It is the final leak detection step after the pressure test is passed.

The reason,

  • to double check on the Step 1 of refrigerant leak detection,

  • to detect moisture within the system, as moisture ingress might have happened during repair works

The steps are similar to (1), (2) and (3) in Step 1, but this time, gas will not be inserted, but vacuumed out of the air conditioning system by an external compressor.

Vacuum until the pressure within the system is 0 bar absolute.

Wait for a few hours, depending on the size of the air conditioner and monitor the pressure rise.

If the pressure rises until 1 bar absolute, then there is leak.

If the pressure rises, but it is lower than 1 bas absolute, then moisture is present.

Refrigerant leak detection by vacuum

Courtesy for condenser picture: Bryant Air Conditioners

What’s next? Either remove the moisture, or repair, and redo the refrigerant leak testing.

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