• SkillCat Team

Leak Repair in Type 2 HVAC Equipment

Updated: Apr 7

EPA Type 2 Chapter 2

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Leak Detection


This module walks through different methods to detect a leak in a refrigeration system. Skip to quiz!



General Indicators of Leak


Recall that leaking of a refrigeration system means that the refrigerant fluid leaks out of a system and into the atmosphere. If a leak is not fixed in time, it will result in all the refrigerant leaking out, and the system will not function.


While troubleshooting a faulty system, one can look for visual indicators to conclude a leak in the system.


Low refrigerant in a system due to leaks will lead to over-pressurizing the remaining refrigerant. It is because the system has to provide the same cooling effect but with a lower amount of refrigerant. Recall that increasing pressure will also increase the temperature of the refrigerant.

An increase in the temperature of the refrigerant in the system leads to high superheat in the system. Excessive superheat is an indicator of a leak in high-pressure systems having a capillary tube. Let us understand this slide a bit more.


Superheat is the difference between the actual temperature and the ideal refrigerant temperature on the suction side. A technician can measure the actual temperature on the suction side of an appliance. Technicians can get the ideal temperature from the equipment’s nameplate.


A Capillary tube is a thin cylindrical copper tube, a type of metering device generally found in older systems. The TEV(Thermal Expansion Valve) is also a type of metering device that is relatively new, more sophisticated, and precise. Superheat is automatically maintained constant by the TEV.


To reiterate the whole concept:

  • Low refrigerant in the system will increase its temperature.

  • An increase in the temperature of the system leads to high superheat.

  • Excessive superheat is an indicator of a leak in a high-pressure system having a capillary tube

Hermetic System

A hermetic system refers to a system that has a hermetic compressor installed in it. A hermetic compressor has all the major components of the compressor in just one single structure. This type of system is the most common type of system and can be seen in residential, commercial, and industrial refrigeration systems.


Recall that one of the functions of refrigerant oil is to provide internal sealing of the system. The refrigerant oil forms a layer inside the system's tubings and joints. Any leak in the system would first push out the system's refrigerant oil.


This would leave oil traces on the system or the floor of the system. Oil traces is an indicator that the hermetic system is leaking. While inspecting any system, traces of oil are ideally the first signs a technician should look for.


Belt-Driven Non-Hermetic System


In a belt-driven non-hermetic system, the compressor motor and the compressor are in different structures and connected by a rubber belt. Unlike the hermetic type, it does not have its components in a single shell. This type of system can be seen mostly in industrial refrigeration systems.


A Rotating shaft seal is used at the junction where the metallic shaft connects to the compressor. Rotating shaft seals have rubber seals for the purpose of sealing. If a system is non-working for several months, the rubber seals become hard and cannot perform sealing, causing leaks in the system.


To reiterate the whole concept:

1. A Rotating shaft seal is used at the junction where the metallic shaft connects to the compressor.

2. In a belt-driven non-hermetic system, that has not been used for many months, the rotating shaft seal is most likely to leak.



Leak Detection Methods


Let us have a look at some methods to detect leaks in a system. In the absence of any specific indicators of leaks, these methods have to be used to find leaks.

Ultrasonic Leak Detectors An ultrasonic leak detector works by amplifying the sound of the gas escaping a system. Electronic Leak Detectors They have an electronic circuit in them which can detect the presence of particular refrigerants. Both methods are used to detect broad areas of a leak.


Recall that a soap bubble leak detection test is used to pinpoint the specific area of the leak. Soap bubble leak detection test is generally the most effective method of leak detection as it pinpoints leaks and tells the exact location of leaks to the technician.


Recall that in the nitrogen pressure test also called as standing pressure test, pressurized nitrogen gas is filled in the system.

A nitrogen pressure test is generally the first thing to be done for newly assembled systems or field piped split systems. A field piped system is one that has been installed on-site and not a ready-to-install factory-made system. Examples of field piped systems include residential split AC and residential heat pumps.

The number of leaks in a field piped system, or a newly assembled system depends on the technician's skill working on it. So it is important to perform a nitrogen pressure test on such systems to ensure that the system is leak-free.


Recall the use of a trace gas with nitrogen in a standing pressure test. If a trace amount of other gas is necessary during leak checking, the best choice for the trace gas is the system’s design refrigerant itself. For example, an R407C system should use R407C as a trace gas with nitrogen for leak detection.


In this module, we discussed a few indicators of leaks and particular systems in which they can be used. We also refreshed methods to detect leaks and learned about the use of trace gas while detecting leaks.



Leak Repair

In this module, we will learn about EPA’s classification system and leak rates defined for the particular systems. We will also learn about the process defined by EPA for repairing leaks. Skip to quiz!


Leak Repair Categories


Many types of refrigeration systems are used in the market. EPA classifies the different types of systems available into four categories.

The systems are classified based on the purpose they serve. They are:

  • Comfort cooling systems

  • Commercial refrigeration systems

  • Industrial process refrigeration

  • All other appliances

Let us have a look at each category.


Comfort cooling systems are systems used to provide cooling and humidity control in places occupied mostly by humans.


Residential houses, offices, and commercial buildings are few such examples of places having comfortable cooling systems. Examples of such systems include chillers, commercial split systems, and packaged rooftop units.

Commercial refrigeration systems are appliances used in retail food and cold storage sectors.

Some examples include supermarkets, restaurants, other foodservice chains, convenience stores, and cold storage to store goods like meat and dairy products.


Industrial process refrigeration is directly linked to industrial processes. These systems are complex, customized systems used in the chemical, pharmaceutical, petrochemical, and manufacturing industries.


This sector also includes industrial ice machines, appliances used directly in electricity generation, and ice rinks. Note that if one appliance is used for both IPR and other applications, it will be considered IPR equipment if 50% or more of its capacity is used for IPR systems.

Recall that leak rate is the rate at which an appliance is losing refrigerant due to leaks. According to the previous slide classifications, EPA defines the maximum leak rates for these systems.


Just as we say ‘To err is Human,’ no appliance can be made entirely leak-free. Despite all measures to prevent leaks, all systems have a very tiny bit of leakages from them. This leak is acceptable until the leak rate does not exceed the maximum leak rates set by the EPA.


The maximum leak rate is that leak rate above which the system must be repaired for leaks. The maximum leak rate is also called the trigger leak rate or threshold leak rate. Remember these names!

The following are the maximum leak rates for a 12-month period

Appliance Type Leak Rate

Comfort cooling systems 10%

Commercial refrigeration 20%

Industrial Process Refrigeration (IPR) 30%

All other appliances 10%

Remember these numbers!

The leak rates in the table give the maximum leak rate set by the EPA. They apply for all systems having 50 pounds or more amount of refrigerant. If the leak rate of a system exceeds the maximum leak rate given in the table, it must be repaired for leaks.

Leak Repair Procedure


Now that we know the maximum leak rates for all types of appliances, we must repair an appliance if it leaks beyond the maximum rate.

If an appliance has a leak rate higher than the maximum leak rate set by EPA, the owner of that appliance has the following options:

  • To repair the appliance.

  • To mothball the appliance or the specific leaking component(s).

  • To retrofit the appliance.

  • To retire the appliance.

Let us look at each of these options in detail.


The owner of an appliance must get the leak repaired after detecting it. After repairing the leak, it is compulsory to verify the results whether the system is still leaking or not.


The EPA states that two leak verification tests are required after repairing an appliance. A leak verification test is the set of steps to confirm that the appliances’ leak rate is below the maximum leak rate.

The two leak verification tests are: Initial Leak Verification Test It should be performed right after the leak is repaired and before filling the system back with refrigerant. Follow-up Leak Verification Test It should be performed after the appliance returns back to normal working conditions. (Usually within 10 days of leak repair)


If any of the two leak verification tests fail, it means that the system is still leaking. In such situations, the owner must further repair the appliance or go for any of the next steps.


Mothballing an appliance means to

  1. Evacuate it to at least atmospheric pressure

  2. Isolate it from the other components and

  3. Temporarily shut it down.

Recall that evacuating equipment means removing all the air out of the system.

Isolating is separating the appliance or a piece of equipment from the rest of the system. Equipment is mothballed if the repair process is taking too long or some replacement piece of equipment is not available at the moment.


Retiring the appliance means to put it out of service and properly dispose of it. If a leak is irreparable, we can retire the appliance and dispose of it.


Recall that retrofitting is when we adapt and make changes to the equipment so that we can use a new refrigerant in it. If a leak is irreparable, we can retrofit the appliance to use a new refrigerant in it.


In this module, we discussed EPA’s classification of systems. We also went through the maximum leak rates for these systems. Finally, we also learned about the procedure to be followed while repairing leaks in a system.



Leak Repair Timeframe

In this module, we will discuss the time frame to repair any leak. We will also learn some EPA regulations and recordkeeping requirements after the leak have been repaired. Skip to quiz!


Time Frame Requirements


If a technician detects a leak in any equipment having 50 or more pounds of refrigerant, the owner or operator must get the leak repaired within 30 days of detecting it. An owner is the one who owns the appliance. An operator is the one who is using the appliance.

In addition to repairing the leak, leak verification tests must also be conducted within the 30-day period to confirm the result. Recall the two leak verification tests

  • Initial leak verification test and

  • Follow-up leak verification test.

EPA states that the follow-up leak verification test must be conducted within 10 days of the leak repair. The follow-up leak verification test is compulsory for an appliance having 200 pounds or more refrigerant.


If any of the leak verification tests fail, the owner or operator of the appliance can conduct additional repairs and repeat the process within the 30-day window.

If the owner or operator fails to repair the appliance, they must develop a retirement or retrofit plan. The plan must be executed within 12 months. The appliance can continue to operate without repair for 12 months, before which the appliance must be retrofitted or retired.


Recall that natural refrigerants like ammonia (R717) and carbon dioxide (R744) are exempt from the venting prohibitions. The owner or operator has 18 months to retrofit or retire a leaking appliance if the replacement uses a refrigerant exempt from the venting prohibition.


Leak Inspection Frequency


After any system that has been repaired for leaks, the owner or operator must get a leak inspection done after a specific time. Leak inspections should be done until the owner/operator can show that the leak rates for one year are lower than the maximum leak rates.

Recall the maximum leak rates:

Appliance Type Leak Rate

Comfort cooling

systems 10%

Commercial refrigeration 20%

Industrial Process

Refrigeration (IPR) 30%


For Comfort Cooling Systems having more than 50 pounds of refrigerant, Leak inspections should be done once per calendar year (Jan - Dec).


For Commercial refrigeration and IPR (Industrial Process Refrigeration) systems having 50 to 500 pounds of refrigerant, Leak inspections should be done once per calendar year.


For Commercial refrigeration and IPR systems having 500 pounds or more refrigerant, leak inspections:

  • Should be done once every 3 months.

  • Performed until the owner or operator can show that the leak rate has not exceeded 20% (commercial refrigeration) or 30% (IPR) for four quarters (one year).

Extending Deadlines


The EPA allows certain situations in which the 30-day deadline can be extended. These may include extensions due to federal, state, or local regulations.

The leak repair deadline can also be extended if a component is not available at the moment. To extend the deadline, the owner or operator cannot use a reason that a certified service technician is unavailable.


In this module, we discussed the timeframes for repairing a leak. We also learned about how frequently should a leak inspection be done. Finally, we also discussed the situations in which the leak repair deadlines can be extended.



Leak Repair Regulations



In this module, we will discuss about the regulations to repair any leak. We will also learn some EPA regulations and recordkeeping requirements after the leak has been repaired. Skip to quiz!



Leak Repair Regulations


Now that we know the deadlines to be followed while repairing any leak, let us look at some EPA regulations.

Recall that refrigerant charge is the term used for the total amount of refrigerant present in the system. It is necessary to calculate the refrigerant charge while calculating the leak rate and filling the system with refrigerant.


EPA allows calculations based on component and pipe sizes. The method includes getting the refrigerant charge from the system's nameplate and adding excess refrigerant based on the system's pipe sizes and accessories. A technician need not memorize any formula, but the calculation method must be kept in mind.


Recall that topping off means adding additional refrigerant to the appliance without checking for, and fixing, any leaks. While topping off refrigerant in any system containing more than 50 pounds of refrigerant, it is compulsory to calculate the leak rate first.

Recall that topping off means adding additional refrigerant to the appliance without checking for, and fixing, any leaks. While topping off refrigerant in any system containing more than 50 pounds of refrigerant, it is compulsory to calculate the leak rate first.


Seasonal variance in the process of adding/removing refrigerant from an appliance during different seasons. Addition/removal of refrigerant is needed as external environmental conditions change in different seasons. Calculating leak rate is not required while adding refrigerant for seasonal variance.

Recordkeeping and Reporting

Record keeping is the task of maintaining the complete details about

  • Leak inspections

  • Leak repairs, and

  • The tests performed to verify repairs of leaking appliances.

The technician working on the system must provide all the records.


As per the EPA, it is compulsory to keep the records for any appliance having 50 or more pounds of ozone-depleting refrigerant for a minimum of 3 years. The owner and operator of the equipment are responsible for keeping the records.


As per EPA, along with other details, the records should primarily include:

  • Location and date of the recovery

  • Type of refrigerant recovered

  • The total amount of refrigerant recovered

  • Amount sent for reclamation

The owner and operator can maintain a hard copy or an electronic copy. The records must be kept on site where the appliance is installed.


Technicians and HVAC servicing companies should also keep records of appliances having refrigerant amounts between 5 and 50 pounds when disposing of them. The records of disposal must be kept for a minimum of 3 years.

At times EPA requires the owner or operator of an appliance to record and submit a report about the leak to EPA. A report must be submitted to EPA if the systems’ leak rate in one calendar year (Jan - Dec) is higher than 125% of the total refrigerant amount in the system.


A 125% leak rate would mean that :

  • The system once leaked completely(100% leak).

  • It was repaired and filled back with refrigerant.

  • A quarter (25%) of the refrigerant leaked out again.

And all of this took place in one calendar year(Jan - Dec).


The submitted report must describe the owner/operator’s efforts to identify and repair the systems leaks. Other than this situation, it is generally not required to send a report to the EPA.


In this module, we discussed the regulations for repairing a leak and calculating the leak rate. We also learned about the recordkeeping and reporting requirements by EPA.




Question #1: Which of the following is an indicator of a leak in a high-pressure system with a capillary tube?

  1. High head pressure

  2. Low water temperature

  3. Excessive superheat

  4. Frequent purging

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Answer: Excessive superheat

If a high-pressure system with a capillary tube has a high value of superheat, it is an indicator that there is a leak.

Question #2: When first inspecting a hermetic system known to be leaking, you should look for;

  1. Frost on the tubing

  2. Puddles of refrigerant

  3. Particles of filter drier core

  4. Traces of oil

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Answer: Traces of oil

While inspecting any hermetic system, traces of oil are ideally the first signs a technician should look for.

Question #3: Which part of a belt-driven non-hermetic compressor is most likely to leak if the compressor has not been used for several months?

  1. Suction service valve

  2. Rotating shaft seal

  3. One or both of the king valves

  4. Head gasket on the discharge side

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Answer: Rotating shaft seal

If a belt-driven non-hermetic compressor has not been used for several months, rubber seals in the rotating shaft seals become hard.

A hard seal cannot perform its function of sealing the system. Insufficient sealing will let the refrigerant oil leak out of the system.

Question #4: To pinpoint refrigerant leaks, we use the method;

  1. Ultrasonic Leak Detector

  2. Soap Bubble Leak Detection Test

  3. Electronic Leak Detection

  4. Leak Sniffing Method

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Answer: Soap Bubble Leak Detection Test

The best use for testing a system for leaks using soap bubbles is to pinpoint the leaks.

Question #5: After installation of a field piped split system, the unit should first be pressurized with;

  1. air and leak checked.

  2. R-22 and leak checked.

  3. R-410A and leak checked.

  4. nitrogen and leak checked.

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Answer: Nitrogen and leak checked.

Any field piped system should first be pressurized with nitrogen and leak checked. The number of leaks in a field piped system depends on the technician's skill working on it.

So it is important to perform a pressure test and detect leaks first.

Question #6: What is the first thing to do when a new system has been assembled (built up), and is ready for testing?

  1. Pull a vacuum.

  2. Pressurize with an inert gas and leak check.

  3. Pressurize with the refrigerant to be used in the system.

  4. Introduce an initial charge of refrigerant and start the compressor.

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Answer: Pressurize with an inert gas and leak check

Any newly assembled system should first be pressurized with nitrogen and leak checked. The number of leaks in a newly built system depends on the technician's skill working on it.

So it is important to perform a pressure test and detect leaks first.

Question #6: When a trace gas becomes absolutely necessary, which of the available gases should be used to help locate a leak?

  1. Nitrogen with HCFC R-22

  2. R-22 due to its universal system compatibility and its miscibility with various oils

  3. Nitrogen with a trace amount of the system’s design refrigerant

  4. Nitrogen with HFC R-410A

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Answer: Nitrogen with a trace amount of the system’s design refrigerant

If a trace amount of other gas is necessary during leak checking, the best choice for the trace gas is the system’s design refrigerant itself.

Nitrogen gas should be used along with trace gas to help locate leaks.


Question #7: Which leak repair category does the EPA define as the refrigeration appliances used in the retail food and cold storage warehouse sectors?

  1. Commercial refrigeration

  2. Industrial process refrigeration

  3. Comfort cooling

  4. Ice making refrigeration

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Answer: Commercial refrigeration

EPA classifies appliances used in retail food and cold storage warehouse sectors as Commercial Refrigeration Systems.

Question #8: A company uses a chiller that diverts 55% of its cooling capacity to one of its manufacturing lines and 45% of its cooling capacity to air condition the office spaces. Which leak rate category would this chiller be in?

  1. Commercial refrigeration

  2. Industrial process refrigeration

  3. Comfort cooling

  4. Ice making refrigeration

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Answer: Industrial process refrigeration

If any appliance uses more than 50% of its capacity for industrial processes (manufacturing line in this case), it is classified as Industrial Process Refrigeration System.

Question #9: Starting in 2019, what leak rate triggers the EPA requirement that commercial refrigeration systems containing 50 pounds or more of R-22 be repaired?

  1. 10%

  2. 20%

  3. 30%

  4. 40%

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Answer: 20%

The maximum leak rate set by EPA for a commercial refrigeration system is 20%. If a commercial refrigeration system has a leak rate higher than 20%, then it must be repaired.

Question #10: Which of the following is NOT required to mothball an appliance using an ozone-depleting refrigerant?

  1. Shut down the appliance temporarily

  2. Remove the appliance and store it in a warehouse at the facility

  3. Recover the refrigerant from the isolated section or component

  4. Recover refrigerant to at least atmospheric pressure

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Answer: Remove the appliance and store it in a warehouse at the facility

The other options are processes actually involved during the process of mothballing an appliance. Removing the appliance and storing it in a warehouse is not a step included in mothballing an appliance.

Question #11: After a leak repair of a cold storage refrigeration system using 2500 pounds of R-410A and a successful initial verification test, when must a follow-up leak verification test be conducted?

  1. The same day

  2. The next day

  3. Within 10 days

  4. Within 30 days

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Answer: Within 10 days

As the given system contains more than 200 pounds of refrigerant, it is compulsory to perform a follow-up leak verification test within 10 days of repairing the leak.

Question #12: How long do owners or operators of an appliance with a full charge of 50 or more pounds of ozone-depleting refrigerant have to retire an appliance if the replacement uses a refrigerant that is exempt from the venting prohibition?

  1. 3 months

  2. 6 months

  3. 12 months

  4. 18 months

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Answer: 18 months

The replacement uses a refrigerant exempt from venting prohibitions. The owner or operator has 18 months to retire or retrofit the appliance in such a case.

Question #13: A customer has an industrial process refrigeration system that contains 2000 pounds of R-22 that have exceeded the applicable leak rate threshold. How often is the customer required to perform a leak inspection?

  1. Every month

  2. Every 3 months

  3. Every 6 months

  4. Once per calendar year

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Answer: Every 3 months

The given system is an IPR system and contains more than 500 pounds of refrigerant. it is compulsory to perform a leak inspection every 3 months after repairing the system.

Question #14: A supermarket rack that contains 400 pounds of R-410A that have exceeded the applicable leak rate threshold. How often is the customer required to perform a leak inspection?

  1. Every month

  2. Every 3 months

  3. Every 6 months

  4. Once per calendar year

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Answer: Once per calendar year

The given system is a commercial refrigeration system. It falls in the category of systems having 50 to 500 pounds of refrigerant. It is compulsory to perform a leak inspection once per calendar year after repairing the system.

Question #15: Which of the following cannot be used as a reason to extend the appliance repair deadlines?

  1. Requirements of state regulations make the repair within 30 days impossible.

  2. A necessary component is not available.

  3. The appliance is located in a radiologically contaminated area.

  4. A certified service technician is not available.

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Answer: A certified service technician is not available

Out of all the other reasons, not having a certified service technician available for service cannot be used as a reason to extend the leak repair deadline.

Question #16: To determine if the system is leaking more than the maximum rate, the EPA allows the use of which methods to calculate the full charge?

  1. Calculations based on power consumption, in kWh.

  2. Calculations based on tonnage.

  3. Calculations based on component and pipe sizes.

  4. Calculations based on the BTU capacity of the system.

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Answer: Calculations based on component and pipe sizes EPA allows the use of calculations based on component and pipe sizes to determine the full charge in the system. Question #17: Which of the following refrigerant additions, to an appliance that contains 50 or more pounds of an ozone-depleting refrigerant, triggers the requirement to calculate the leak rate?

  1. Following a retrofit

  2. During the installation of a new appliance

  3. During a qualified seasonal variance

  4. When topping off the system

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Answer: When topping off the system The requirement to calculate the leak rate gets triggered while topping off refrigerant in any system containing more than 50 pounds of refrigerant. Question #18: How long must owners and operators of regulated appliances normally containing 50 or more pounds of CFC refrigerant keep records of leak inspections, initial leak verification and follow-up verification tests?

  1. 2 years

  2. 3 years

  3. 5 years

  4. Life of the appliance

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Answer: 3 years Owners and operators of regulated appliances containing 50 or more pounds of regulated refrigerant should maintain all records for at least 3 years. Question #19: For what period should an HVAC servicing company keep records for a disposed appliance with a charge between 5 and 50 pounds?

  1. 2 years

  2. 3 years

  3. 5 years

  4. 10 years

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Answer: 3 years An HVAC servicing company disposing of an appliance with a charge between 5 and 50 pounds must keep the records for a minimum period of 3 years.


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