Step by Step Guide to Refrigeration Leak Detection

Current EPA regulations recommend and/or require leak detection and repair when it has been determined that a system is losing refrigerant.  This 10 step guide to refrigeration leak detection will help you be able to determine if the evaporator has a leak using today’s best practices.

  1. Know your leak detector and how to correctly operate it. Does it respond to concentrations of refrigerant or changes in concentration of refrigerant?  A good leak detector is only as good as its operator.
    • Never camp on a suspected leak with your meter. Most electronic meters auto adjust to concentrations of refrigerant, giving the illusion that it is not a leak after all.  Keep moving the probe and note the areas of concentration.  Use a visible method (bubble solution) to pinpoint the leak.
      • Heated Diode, Heated Pentode, Corona Shield, Heated Electrolyte or any other method that breaks down the refrigerant with heat places the sensor directly in the stream of refrigerant, resulting in sensor degradation. High concentrations of refrigerant will quickly degrade a sensor. For this reason, never open a jug of refrigerant and insert your sensor into the stream of refrigerant as a means of checking your meter.  You will quickly ruin your sensor and need a replacement.  Heated Sensor technology type sensors will last for a maximum of 100 hours but should typically be replaced after 20 hours unless it can be determined by a calibrated reference leak that the sensor is still capable of sensing small concentrations of refrigerant.
      • Infrared Leak Detectors look at gasses in the refrigerant region of the infrared spectrum. The sensor is not directly in the sensing stream and doesn’t suffer degradation from excess exposure. Sensor life expectancy is over 1000 hours and in some cases – the life of the meter.
  1. Start your meter outside and let it self-zero before entering the residence. Use a calibrated reference leak to ensure that your meter is capable of detecting a refrigerant leak.
    • Starting outside gives your meter the greatest chance to zero itself without any refrigerant exposure.
  2. Enter the space. If your meter notifies of refrigerant, go back outside and let it zero.  Return indoors.  If your meter notifies again, it can safely be determined that there is refrigerant concentration in the space.  (Every detection must be repeatable to confirm a leak is present.)
  3. Shut off the HVAC System, making sure the blower is not running. Wait 10 minutes to allow leaking refrigerant to settle and concentrate.
  4. Go to the indoor evaporator.
  5. Remove the condensate drain fitting.
  6. Check in the condensate pan with your electronic leak detector probe.
    • If it picks up refrigerant, remove it and let it zero.
    • Check the pan again.
    • If it picks up refrigerant again, it’s been determined that a leak is present somewhere in the evaporator section, but may not be in the coil itself. Further investigation is required.
  7. Remove the evaporator door to expose the coil and mechanical connections.
  8. Check all mechanical connections – if possible use a visible method such as bubble solution on the mechanical joints where the TXV, Equalizing Tube, Orifice, Schrader Fitting, etc. are connected or capped.
  9. If no leak can be located on a mechanical joint, it’s safe to condemn the coil as a leaker.


Remember, it’s important to know how to correctly operate your Leak Detector and check it regularly against a calibrated reference leak.  This will help ensure that your tools are working properly.  Then be sure to use this guide, and our article over refrigeration leak detection available here, to ensure you’re using the best practices for leak detection.  Last, don’t condemn the evaporator until you have proved it is leaking.

For more technical support on this issue or other HVACR related problems, call our service tech department at 1-800-322-9675, or e-mail us at

Paul Flora
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