Refrigerant Leak Causes & Tests: HVAC Technician Guide

HVAC technicians monitor the refrigeration weight and pressure of a chiller in order to correctly recharge the unit (image source)

If a client calls complaining about an air conditioner or heat pump not working properly, a refrigerant leak is one possible source of the problem.

Not only do refrigerant leaks impair system performance, waste money, and hurt the environment, they're also poisonous to humans.

Over-exposure to Freon, for example, can cause breathing problems, fluid buildup in the lungs, organ damage, and even sudden death. Testing for and addressing leaks is a very important part of an HVAC technician's job.

What causes refrigerant leaks and what are the best ways to test for them?

In this post, we'll look at how leaks develop in the first place, and a various tools and techniques the HVAC technician will use to detect them.


 Common Causes of Refrigerant Leaks

You'll find that some clients buy into the myth that an a/c unit or heat pump "uses up" refrigerant over time. In reality, these units have a sealed refrigerant system, also known as a hermetic system. Refrigerant doesn't get "burned up" with use, and shouldn't need to be replenished—unless there is a leak.

There are several common causes of refrigerant leaks, including:

A leaking schrader valve. HVAC techs use the schrader valves to temporarily access systems for pressure measurement. If the valve gets stuck, or its rubber seal deteriorates, refrigerant can leak through.

System vibration. Over time, natural system vibration can cause joints and connections to come loose or  sustain damage. For example, clamps can come loose on copper tubing, allowing it to rub against the strut, which causes holes to form.

Corrosion. Corrosion can attack the copper tube walls of the indoor coil, causing refrigerant leakages in several locations. In the case of heat pumps, accumulators made of steel usually begin to rust out after a few years, allowing refrigerant to escape through small holes. In situations like these, both the coil and the accumulator must be replaced.

Faulty flare connections. There can be several reasons for faulty flare connections that result in refrigerants leaks, including flares that are too small or thin, have been over-tightened, or improperly sealed.

Damaged line set.  Sometimes the line set that carries the refrigerant back and forth from the condenser to the evaporator coil gets damaged—by a lawn mower, for example, or construction work. Refrigerant will leak from the line set until an HVAC technician roots out the source of the problem and makes a repair.


4 Ways an HVAC  Technician Tests for Refrigerant Leaks

If you suspect a refrigerant leak is responsible for your client's system problem, you'll run tests to confirm and locate the source of the leak. There are a few different testing methods an HVAC technician can use:

Electronic leak detector: You can run this tool along the refrigeration components to detect leaks. However, it can only scan reachable components—parts it can touch. You might not be able to position this tool in all the places a leak may be.

Nitrogen leak test: This is the preferred approach for many HVAC techs. After removing any Freon or Puron, you'll pump compressed nitrogen into the refrigeration system. You will be able to hear if leaks are present, similar to when you pump air into your bicycle tire, and can hear it escaping through a small tear or hole.

Technicians also watch the gauges for any pressure changes during the nitrogen test. If there is a leak, the pressure will fluctuate.

Soap bubble test: The HVAC technician makes a soapy solution using dishwasher liquid and water, and then sprays it onto the test area. If there is a leak, it will cause bubbles to form. There are also specially formulated, patented foaming solutions on the market that can be used to run the bubble test.

Dye Testing: For this approach, you will add ultraviolet dye to the refrigeration system. Viewed under a black light, the dye will reveal even the smallest leaks.

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