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Leaks in HVAC Equipment

EPA 608 Core Chapter 10

Causes of Leaks

In this module, we will discuss the various causes of leaks and their effect on the HVAC system. Skip to quiz!

Refrigerant Leaks

A refrigerant charge refers to how much refrigerant is contained in the system. For example, think of how many ounces of water are in a glass. The amount is typically given in units of pounds (lb).

HVAC equipment needs to be charged with refrigerant in order to operate. If a piece of HVAC equipment does not have enough refrigerant, it cannot work properly. Typically, it will lead to reduced cooling capabilities.

For example, if an air mattress has even a small leak or hole, it will leak and no longer work. Eventually, all air may escape from the mattress.

Effects of Leaks

A refrigerant leak may mean a harmful substance is released into the atmosphere. This is especially true if we are dealing with CFC or HCFC refrigerants, which deplete the ozone layer.

Refrigerants can also be harmful to humans if it is toxic and leaked indoors.

It’s recommended to check for leaks frequently because leaks are easier to repair when they are small. Large leaks are harder to repair and can cause safety hazards.

Both the repair of a leak and the additional replacement refrigerant will cost money. The cost of both will only increase with a larger leak.

Why Leaks Happen

We need to check for leaks before charging a system. Recall that charging means to replenish a system with refrigerant gas.

We find that leaks commonly occur at the following locations in the system:

  • Piping connections

  • Equipment Coils

  • Valves, and

  • Where refrigerant piping enters or leaves a home or building

Leaks can occur for various reasons including the following:

  • Wear and tear

  • Poor initial installation

  • Other construction.

All equipment, HVAC or not, will go through wear and tear. As equipment ages, the possibility of a leak increases. This is just like us humans. As we get older, we’ll go through wear and tear and will find that our back hurts more, for example.

If the equipment was not installed properly to start with, this can cause leaks that may be costly to deal with later on. This is why only licensed HVAC technicians should be working on these complex systems.

And finally, leaks can occur because of other, non-HVAC construction around the system. For example, a nail could be driven into a refrigerant pipe that is located outside the HVAC equipment. This could damage the equipment and cause a leak.

Repairing Leaks

If we find a leak in the system, we need to then repair the leak. Finding and repairing the leak will help conserve the refrigerant still left in the system.

Imagine knocking over a full carton of milk. The sooner you stand the carton back upright, the more milk there is left in the container.

This is what we want to do with a system leak. Finding and repairing leaks will help save the refrigerant left in the system.

There can be many ways to fix a leak depending on

  • Where the leak is, and

  • How big the leak is.

One option is to solder or braze the leak on copper piping. If the leak is small and contained enough, you can use this method.

A second option is to replace the component that has the leak (such as a coil).

If the leak cannot be fixed, the entire piece of HVAC equipment may need to be replaced. After a leak is repaired, the system should be checked to make sure the repair is working.

To check the fix, you will

  • Evacuate refrigerant piping

  • Pressurize with nitrogen

Gauges will show if the pressure is holding and if the leak was fixed. If the pressure matches the operating pressure of the system, the system can be re-filled with refrigerant.


Leak Detection Methods

This module walks through the various leak detection methods used in the HVAC industry. Skip to quiz!

Signs of Leak

The first sign of a leak is typically a reduced cooling capacity of the HVAC equipment. This can be noticed when rooms are not sufficiently cooled, especially if it used to feel cooler at the same temperature.

The room may simply feel a bit warmer than usual even if the system’s cooling function is on. If HVAC equipment components are working properly, the issue is most likely a leak.

If you find that the system does not hold a vacuum after you evacuate it, this is also a sign of a leak in the system. A system that is leak-free would have no problem holding a vacuum.

Finding Leaks

The first steps to finding a leak are the following options (no equipment required):

  1. Visual inspection

  2. Audible sound

The first step is a visual inspection. When looking over the components of the system, we want to pay attention to any traces of oil on fittings. Oil residue indicates a leak.

Sometimes, a leak can be heard without using any additional equipment. You may hear a hiss, which indicates a potential leak.

Additional methods for detecting leaks are:

  1. Halide Torch

  2. Ultrasonic Leak Detector

  3. Electronic Leak Detector

  4. Soap Bubble Test

  5. Standing Pressure Test

A halide torch consists of a flame that changes color when there is a leak. But halide torches can only be used with certain refrigerants (including R-12 and R-22). Halide torches cannot be used with hydrocarbons because hydrocarbons are highly flammable.

An ultrasonic leak detector works by amplifying the sound of the gas escaping a system. This helps identify the area of leakage.

An electronic leak detector senses the presence of halide gases such as chlorine and fluorine. Both ultrasonic and electronic leak detectors point to the general area of small leaks.

After knowing the general area of the leak, we need to find the exact location of the leak. We can use the soap bubble test to pinpoint the leaks to start on making repairs.

And lastly, we can test for leaks by doing the standing pressure test. For this test, first evacuate the system. Then we will pressurize the system and use an electronic leak detector to see if there are any leaks.

We will discuss this test in detail in the next section.

To summarize, there are many ways of detecting leaks. Generally, we want to start with a visual inspection.

The most effective methods for locating the general area of a small leak are:

  1. Ultrasonic leak detectors, and

  2. Electronic leak detectors


Standing Pressure Test

In this module, we will discuss various procedures and techniques that need to be followed while performing the standing pressure test. Skip to quiz!


As we mentioned, the standing pressure test is when we pressurize the system and then use electronic leak detection to identify the leak.

When we are pressurizing equipment, we want to make sure that we do not exceed the low side test pressure for the equipment.

The test pressure for equipment can be found on the equipment’s nameplate. Make sure you do not exceed the low side test pressure indicated on the nameplate.

We pressurize the system by adding a pressurized gas.

Our options are

  1. Dry nitrogen, and

  2. A mixture of dry nitrogen and a refrigerant gas

    1. For example: Dry nitrogen with R-22 refrigerant

When we mix R-22 with nitrogen to do leak testing, this is called a trace gas. Trace gases are not considered refrigerants under EPA refrigerant management guidelines.


Note that only specific refrigerants can be used for this method. For example, R-22 can be mixed with dry nitrogen to leak check a system. But R-12 cannot be mixed with dry nitrogen for this method.

Before pressurizing the system, we need to start by evacuating the system. We need to first recover the system to 15 psig.

Technicians cannot add nitrogen to a fully charged system. This would contaminate the refrigerant in the system because you would be combining two substances together.

The resulting mix cannot be separated. Imagine adding orange juice to milk. You cannot separate the two liquids after mixing. This is why you cannot add nitrogen to a fully charged system.

By recovering the system to 15 psig, you are leaving some refrigerant in the system. Recall that electronic leak detectors detect leaks by sensing refrigerant in the general area. There has to be refrigerant leaking in order to locate where the leak is.

After pressurizing the system, we locate the leak with the electronic leak detector. Then we have to recover the nitrogen and refrigerant mixture in a separate tank.

If we use the same tank as the one used to contain nitrogen or the refrigerant, it would “cross-contaminate” the tanks. There would be residue left in the tank. If the tank were to be used for nitrogen, you would have the residue of refrigerant. So we need to recover in a separate tank.

The EPA allows technicians to mix R-22 and dry nitrogen to detect leaks. But as we said, once you have a mixture, you cannot use that mixture anywhere else. You also have to recover the mixture in a separate recovery cylinder.

Flammable Refrigerant Procedures

When leak testing a system containing flammable refrigerants such as hydrocarbons (propane, isobutane) or HFOs, we must always install a filter-drier. A filter-drier removes the moisture and contaminants from the refrigerant.

We must also perform a standing pressure test for systems with flammable refrigerants.

For a system containing 50 pounds or more of a refrigerant and with triggered leak rates, two verification tests should be performed. One is done before charging the system and one after the system is working normally.

We will look into the details of the acceptable leak rates for different systems in the courses for Types I, II, and III.


Question #1: Which of the following is not a reason why refrigerant leaks are a concern?

  1. They can easily be fixed by all homeowners

  2. HVAC equipment won’t work properly if there is a leak

  3. They can be costly to find and fix

  4. Refrigerants can be harmful to the environment

Scroll down for the answer...

Answer: They can easily be fixed by all homeowners

Question #2: Which of the following are not common leak locations?

  1. Piping connections

  2. HVAC fan

  3. Coils

  4. Valve connections

Scroll down for the answer...

Answer: HVAC fan

Question #3: What are common ways that leaks can occur?

  1. Wear and tear on old equipment

  2. Poor initial construction

  3. Holes or cracks created accidentally during construction

  4. All of the above

Scroll down for the answer...

Answer: All of the above


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