5 Universal Certification Review and Practice
Review Section 608 certification scope, Core refrigerant principles and safety, and the distinct recovery and service considerations for small, high-pressure, and low-pressure appliances.
Certification scope and exam format
requires knowledge of the Core material and all three equipment-specific sections. The Core covers shared principles and requirements, while Types I, II, and III address different appliance categories and service considerations.
The exam structure is 25 Core questions and 25 questions for each type, for 100 questions total. Closed-book exams require a score of at least 70 percent. A exam taken by mail has a different passing threshold and cannot be used toward . The Core exam must be proctored for , and certification exams must be administered by an EPA-approved certifying organization.
Core: Shared principles and requirements, including environmental effects, regulations, refrigerants, , safety, and shipping.
: Small appliances.
: High- and very-high-pressure appliances, excluding small appliances and motor-vehicle air conditioners (MVACs).
: Low-pressure appliances.
Environmental protection and the refrigeration cycle
CFCs and HCFCs contain chlorine. When released, they can reach the stratosphere, where ultraviolet light frees chlorine that contributes to ozone depletion. Many refrigerants can also contribute to climate change. Section 608 prohibits knowing release of covered refrigerants during service, maintenance, repair, or disposal, except for limited regulatory exceptions. Recover refrigerant with properly certified equipment rather than intentionally venting it.
A refrigeration system moves heat by circulating refrigerant through four basic processes:
Evaporation: Low-pressure liquid absorbs heat in the evaporator and boils into vapor.
Compression: The compressor raises the vapor’s pressure and temperature.
Condensation: High-pressure vapor rejects heat in the condenser and becomes liquid.
Metering: The expansion device reduces liquid pressure before the refrigerant returns to the evaporator.
A refrigerant’s saturation temperature changes with its pressure. Use a pressure–temperature chart for the correct refrigerant, and distinguish gauge pressure (psig) from absolute pressure (psia). Pressure readings, oils, and operating characteristics should not be assumed interchangeable between different refrigerants.
Refrigerant handling and cylinders
Refrigerant handling has three distinct terms:
removes refrigerant from equipment and stores it in an external container; it need not be cleaned.
cleans recovered refrigerant for reuse, generally by oil separation and filtration or drying.
reprocesses refrigerant to an applicable purity standard, such as AHRI Standard 700, and verifies it analytically.
Do not mix refrigerants in a cylinder. Identify the refrigerant before connecting equipment. Mixing can contaminate refrigerant and complicate reuse or , and mixed or contaminated refrigerant may require specialized handling and .
Use approved, refillable cylinders; never refill disposable cylinders. Do not overfill a cylinder: leave room for liquid expansion and follow its fill limit and applicable procedures. Secure cylinders during storage and transport, use required markings, and follow hazardous-material shipping rules.
Safe service practices
Wear appropriate eye protection and gloves. Liquid refrigerant can cause frostbite, vapor can displace oxygen, and exposure to some refrigerants can affect the heart. Use ventilation and follow the refrigerant’s safety information. Do not energize a hermetic compressor while it is under vacuum.
When pressure-testing or leak-testing a system, use dry nitrogen—not oxygen or compressed air—when appropriate. Use a regulator and pressure-relief protection, and do not exceed the appliance’s permitted test pressure. Oxygen or air mixed with oil and exposed to pressure can create a fire or explosion hazard.
: Small appliances
covers small appliances, generally factory-charged, hermetically sealed appliances containing five pounds or less of refrigerant. Examples include household refrigerators, freezers, and room air conditioners.
Service access and appliance construction affect the appropriate method. requirements depend on the appliance and equipment. Small-appliance disposal rules allow specified or evacuation methods; do not substitute a percentage-based disposal rule for the requirements that apply to another service situation. An exception for a particular disposal activity does not generally authorize service work without the required certification.
: High-pressure appliances
covers high- and very-high-pressure appliances, excluding small appliances and MVACs. Common examples include many residential and commercial air conditioners and commercial refrigeration systems. Recognize the system components and the refrigerant’s state at each location.
Liquid can be faster than vapor-only when the equipment and procedures permit it. Follow the required for the equipment and situation. After , check for : a pressure rise can indicate refrigerant remains in liquid or oil and is coming out of solution or evaporating.
EPA evacuation levels vary according to pressure class, appliance charge, and whether the equipment was made before or after November 15, 1993. For example, for a high-pressure appliance charged with 200 pounds or more, the specified level is 4 inches of mercury vacuum with pre-1993 equipment and 10 inches of mercury vacuum with post-1993 equipment. These are regulatory evacuation values, not universal targets for every task.
: Low-pressure appliances
covers low-pressure appliances, especially large centrifugal chillers. Parts of a low-pressure system can operate below atmospheric pressure, allowing air and moisture to leak inward. Excessive purge-unit operation can indicate that air or other noncondensables are entering the system.
Follow the applicable evacuation requirements and use proper leak-test methods. Hot water or a system heating or pressurization device is preferred for leak testing low-pressure systems; nitrogen is another method where appropriate. Use the specified maximum test pressure and do not overpressurize the chiller.
During evacuation, circulate or remove water from chiller tubes as needed to prevent freezing. After reaching the required vacuum, wait and check for pressure rise before opening the system. When recharging, introduce vapor before liquid as required to reduce the risk of freezing water in the tubes.
Integrated review
Use these review points to check the distinctions and conditions covered in the guide:
, , and : removes refrigerant; cleans it for reuse; processes it to a specified purity standard.
Mixing refrigerants: Mixing can contaminate refrigerant and make it difficult to reuse or reclaim.
Certification scope: Universal covers Core and Types I, II, and III. A low-pressure centrifugal chiller falls under .
Excessive purge operation: This can indicate air or other noncondensables entering a low-pressure system.
Pressure testing: Use dry nitrogen with suitable pressure controls when appropriate, not oxygen or compressed air.
: A pressure rise after or evacuation can indicate refrigerant remains in liquid or oil.
mail-in exam: It cannot count toward , and the Core exam must be proctored.
Chiller tube freezing: Circulating or removing water as appropriate during evacuation helps prevent freezing.
Refrigeration cycle: The evaporator absorbs heat as refrigerant boils.
Evacuation example: A high-pressure appliance charged with 200 pounds or more uses the specified 10 inches of mercury vacuum level with post-1993 equipment; this value is not universal for every task.
Unsafe action: Do not energize a hermetic compressor while it is under vacuum.