EPA 608 Type II Practice Test 3 — Questions and Answers
Question 1: What is subcooling in a high-pressure refrigeration system and how is it measured?
- Temperature of suction gas below ambient; measured at the evaporator outlet
- Temperature of liquid refrigerant below its saturation temperature at the measured pressure; measured at the liquid line (Correct answer)
- Temperature drop across the condenser; measured between condenser inlet and outlet
- Temperature of refrigerant in the receiver below the low-pressure cutout setpoint
Correct answer: Temperature of liquid refrigerant below its saturation temperature at the measured pressure; measured at the liquid line
Subcooling is the number of degrees a liquid refrigerant is cooled below its saturation temperature at a given pressure. It is measured at the liquid line by comparing actual refrigerant temperature to the saturation temperature at the measured liquid line pressure. Proper subcooling (typically 10-20°F) ensures liquid refrigerant arrives at the expansion device without flashing, improving system efficiency.
Question 2: When replacing a TXV (thermostatic expansion valve) on an R-410A system, why must a filter-drier also be replaced?
- TXV replacement voided the drier warranty
- Opening the system introduces moisture that the existing drier may not be able to absorb (Correct answer)
- The drier contains R-410A-specific desiccant that must match the new TXV type
- Filter-driers only last as long as the TXV they are installed with
Correct answer: Opening the system introduces moisture that the existing drier may not be able to absorb
Every time a refrigerant system is opened to the atmosphere, moisture enters. The existing drier may already be saturated from previous moisture absorption and will not be able to handle additional moisture. Replacing the filter-drier whenever the system is opened ensures fresh desiccant is present to absorb new moisture, protecting the system from acid formation and ice blockage.
Question 3: A Type II system has an evaporator saturation temperature of 20°F and a suction line temperature of 45°F. What is the suction line superheat?
- 20°F
- 25°F (Correct answer)
- 45°F
- 65°F
Correct answer: 25°F
Superheat equals the actual suction line temperature minus the saturation temperature at the suction pressure. 45°F (actual) − 20°F (saturation) = 25°F superheat. This value falls within a typical acceptable range for many commercial refrigeration systems. Technicians use this calculation to evaluate whether the expansion device is feeding the evaporator correctly.
Question 4: On a Type II split system, what does an excessively long refrigerant line set do to system performance?
- It has no effect if the pipes are properly insulated
- It increases suction pressure, improving efficiency
- It increases pressure drop and can reduce system capacity and efficiency (Correct answer)
- It only affects performance when outdoor ambient temperature is above 95°F
Correct answer: It increases pressure drop and can reduce system capacity and efficiency
Long refrigerant line sets increase pressure drop in both suction and liquid lines. Suction line pressure drop causes the compressor to operate at a lower suction pressure, reducing capacity and efficiency. Excessive liquid line pressure drop can cause flash gas before the expansion device, further reducing system performance. Line set sizing must account for length and refrigerant type.
Question 5: Which is the correct safety precaution when using an oxy-acetylene torch near refrigerant lines?
- Charge the system to maximum pressure first to prevent air entry during heating
- Ensure all refrigerant is recovered before applying heat, as heat decomposes refrigerant into toxic gases (Correct answer)
- Use only an acetylene torch — never use oxygen as it is prohibited near refrigerants
- Refrigerant must be purged with nitrogen while the torch is in use to prevent mixing
Correct answer: Ensure all refrigerant is recovered before applying heat, as heat decomposes refrigerant into toxic gases
All refrigerant must be recovered before using any heat source on refrigerant lines. When refrigerant (especially CFCs and HCFCs) is exposed to high heat, it decomposes into phosgene gas and hydrogen fluoride/chloride — highly toxic substances. Even small amounts of residual refrigerant can produce dangerous concentrations. NEVER apply heat to a system with refrigerant present.
Question 6: What is the purpose of a "pump-down" cycle in a Type II split system?
- To evacuate the entire refrigerant charge into a recovery cylinder
- To move the refrigerant charge into the outdoor condenser/receiver before service or shutdown (Correct answer)
- To remove air from the suction line before startup
- To lower system pressure to atmospheric before changing filters
Correct answer: To move the refrigerant charge into the outdoor condenser/receiver before service or shutdown
A pump-down cycle uses the compressor to transfer refrigerant from the low side into the condenser and receiver (liquid storage area) on the high side before service or extended shutdown. By isolating the refrigerant in the outdoor unit, the technician can work on indoor components (evaporator, TXV, etc.) with minimal refrigerant exposure. It is not a substitute for full recovery when opening the system.
EPA 608 Type II Practice Test 3
What is subcooling in a high-pressure refrigeration system and how is it measured?