3.9 - Practice Questions

Module: Refrigerants Blends and Lubricants
Covers: Sections 3.1–3.8
Question type: Original EPA 608-style multiple-choice practice
Technical and regulatory verification basis: Module 3 content current through August 7, 2026
Answers: See 3.10 - Answers and Explanations.md

Instructions

• Select the single best answer for each question.
• Complete the set without notes or external references when using it as a readiness check.
• Record a confidence code for every answer:
  • C3 — certain and can explain.
  • C2 — probably correct but not fully certain.
  • C1 — guessed between choices.
  • C0 — no reliable basis.
• Enter every incorrect, C1, and C0 response in the error log.
• Review the detailed answer explanations only after completing all questions.
• A correct guess is not considered mastered.
• Questions are written in original wording and are not actual EPA or certifying-provider examination questions.

Practice Record

• Date:
• Time started:
• Time completed:
• Testing condition: Closed-book
• Question set: Module 3 Practice Set
• Correct answers: ___ / 30
• Low-confidence answers (C0–C1):
• Topics requiring review:
• Open critical safety or regulatory errors after review:

Question 1

What is the primary role of refrigerant in a vapor-compression refrigeration system?

A. To create cold by destroying heat

B. To transfer heat through controlled changes in pressure, temperature, and phase

C. To lubricate the compressor bearings directly

D. To prevent all pressure changes in the system

Question 2

Which statement best describes latent heat during refrigerant phase change?

A. It changes only refrigerant pressure and never involves heat transfer.

B. It changes refrigerant temperature without any change of phase.

C. It is heat absorbed or rejected during a phase change without requiring a corresponding sensible-temperature change.

D. It is heat produced only by the compressor motor.

Question 3

For a given refrigerant at saturation, what generally happens to saturation temperature as saturation pressure increases?

A. Saturation temperature increases.

B. Saturation temperature decreases.

C. Saturation temperature remains fixed for all pressures.

D. Saturation temperature becomes independent of refrigerant type.

Question 4

A refrigerant vapor is at a temperature above its saturation temperature at the measured pressure. How is the vapor described?

A. Subcooled

B. Saturated liquid

C. Two-phase

D. Superheated

Question 5

Which statement about a typical 400-series refrigerant is most accurate?

A. It is always a pure single-component refrigerant.

B. It is always an azeotropic blend with zero temperature glide.

C. It is generally a zeotropic blend whose components can have different liquid and vapor compositions.

D. It must contain chlorine.

Question 6

Which refrigerant-number series is commonly associated with azeotropic blends?

A. 500 series

B. 100 series

C. 300 series

D. 700 series only

Question 7

Which statement best describes a near-azeotropic refrigerant such as a zeotropic blend with a small glide?

A. It becomes a pure refrigerant because the glide is small.

B. It remains a zeotropic blend even though its temperature glide is relatively small.

C. It must be assigned a 500-series number.

D. It cannot experience any composition change.

Question 8

What is fractionation?

A. The normal increase in saturation temperature as pressure increases

B. The conversion of a pure refrigerant into a lubricant

C. The temperature difference between superheat and subcooling

D. A change in blend composition caused by preferential separation or loss of components

Question 9

Why should a zeotropic refrigerant normally be withdrawn from a supply cylinder as liquid?

A. Liquid refrigerant cannot contain more than one component.

B. Vapor withdrawal always raises the refrigerant’s ODP.

C. Liquid withdrawal helps preserve the specified blend composition.

D. Liquid withdrawal guarantees that liquid may be sent directly into a running compressor without control.

Question 10

Which statement best describes recovery of a zeotropic refrigerant blend?

A. Recover only the most volatile component first.

B. Capture the complete remaining blend rather than intentionally separating its components.

C. Recover only vapor because liquid recovery causes fractionation.

D. Add a second refrigerant during recovery to restore the original composition.

Question 11

For a zeotropic refrigerant blend, what does the bubble point represent?

A. The saturated-liquid boundary

B. The saturated-vapor boundary

C. The compressor discharge temperature

D. The temperature of superheated vapor only

Question 12

For a zeotropic refrigerant blend, what does the dew point represent?

A. The temperature at which all liquid becomes subcooled

B. The temperature at the compressor shell

C. The midpoint of the glide range

D. The saturated-vapor boundary

Question 13

Which saturation reference should normally be used when calculating superheat for a zeotropic blend?

A. Bubble point

B. Dew point

C. The arithmetic average of bubble and dew temperatures in every case

D. Cylinder surface temperature

Question 14

Which saturation reference should normally be used when calculating subcooling for a zeotropic blend?

A. Dew point

B. Compressor discharge temperature

C. Bubble point

D. The midpoint of the glide range in every case

Question 15

At the same pressure, which expression represents temperature glide for a typical zeotropic blend?

A. $T_{\text{dew}}-T_{\text{bubble}}$

B. $T_{\text{bubble}}-T_{\text{dew}}$ in every case

C. Superheat plus subcooling

D. Condensing pressure minus evaporating pressure

Question 16

A technician measures only the static pressure of an unknown refrigerant. Why is that measurement insufficient to prove refrigerant identity?

A. Refrigerant pressure never changes with temperature.

B. Every refrigerant has exactly the same pressure-temperature relationship.

C. Pressure can identify a refrigerant only when the compressor is running.

D. Different refrigerants can have similar pressures, and pressure must be interpreted with temperature and other identification information.

Question 17

What does the equipment nameplate most directly identify during refrigerant verification?

A. The guaranteed purity of the refrigerant currently inside the system

B. The refrigerant for which the equipment was designed, subject to any later documented retrofit

C. The refrigerant currently stored in the technician’s recovery cylinder

D. Whether the system contains noncondensable gases

Question 18

Why is cylinder color alone not a reliable method of refrigerant identification?

A. Refrigerant cylinders are never painted.

B. Cylinder color identifies only lubricant type.

C. Color may be inconsistent, changed, faded, or reused and does not prove the actual contents or purity.

D. Color can identify only azeotropic blends.

Question 19

When is a refrigerant analyzer especially useful?

A. When refrigerant identity or purity is uncertain or contamination is suspected

B. Whenever the cylinder label is clear and the refrigerant is known

C. Only when determining compressor amperage

D. Only when measuring refrigerant weight

Question 20

A recovery cylinder contains a known refrigerant. The technician is about to recover an unknown refrigerant from another appliance. What is the best action?

A. Add the unknown refrigerant if its pressure is close to the known refrigerant.

B. Mix the two and relabel the cylinder as a blend.

C. Add the unknown refrigerant only if both are in the vapor phase.

D. Keep the unknown refrigerant separate until it is properly identified or handled as suspect material.

Question 21

Which statement about refrigerant and lubricant associations is most accurate?

A. All HFC systems use mineral oil, while all HCFC systems use PAG.

B. Many older CFC/HCFC systems used mineral oil or alkylbenzene, while many HFC stationary systems use POE; the actual equipment specification still controls.

C. HFC and HCFC refrigerants always use exactly the same lubricant.

D. Lubricant compatibility does not depend on the refrigerant or compressor.

Question 22

Which lubricant is most strongly associated with R-134a motor-vehicle air-conditioning applications?

A. PAG

B. Mineral oil

C. Water-glycol

D. Silicone oil

Question 23

Why is refrigerant-lubricant miscibility important?

A. It determines the cylinder paint color.

B. It determines the refrigerant’s ozone-depletion potential.

C. It influences oil circulation and return to the compressor.

D. It eliminates the need to select the proper viscosity grade.

Question 24

Why is lubricant dielectric strength especially important in hermetic compressors?

A. It determines the refrigerant’s saturation pressure.

B. It prevents all lubricant dilution by refrigerant.

C. It guarantees complete oil miscibility.

D. It contributes to electrical insulation in the environment surrounding the internal motor.

Question 25

Which condition is a possible result of moisture contamination in a refrigeration system?

A. Permanent elimination of refrigerant pressure

B. Acid formation, corrosion, or ice at a small restriction

C. Automatic improvement in lubricant dielectric strength

D. Conversion of a zeotropic blend into an azeotrope

Question 26

What is a common effect of noncondensable gases in a refrigeration system condenser?

A. Lower discharge pressure under all conditions

B. Elimination of condenser heat rejection

C. Increased head or discharge pressure and reduced condenser effectiveness

D. Automatic removal of moisture from the system

Question 27

Which statement correctly compares a filter-drier with deep evacuation?

A. A filter-drier removes moisture and particles, while deep evacuation removes air and water vapor; the two processes perform different functions.

B. A filter-drier removes all noncondensable gases, so evacuation is unnecessary.

C. Deep evacuation filters metal particles from the refrigerant circuit.

D. A moisture indicator performs both functions and makes the filter-drier unnecessary.

Question 28

Which statement best describes a substitute refrigerant marketed as a “drop-in replacement”?

A. It is automatically compatible if its operating pressure is similar.

B. It may always be mixed with the original refrigerant.

C. It requires no evaluation when its GWP is lower.

D. The term should not replace verification of equipment, lubricant, materials, pressure, charging, and safety compatibility.

Question 29

A system is being retrofitted to an approved substitute refrigerant. Which sequence is most appropriate before final charging?

A. Add the substitute first, then determine whether the system leaks.

B. Leave dry nitrogen in the system to improve heat transfer, then add refrigerant.

C. Recover the original refrigerant, complete required modifications and leak repair, pressure-test appropriately, remove the test gas, and evacuate before charging.

D. Mix the original and substitute refrigerants until the pressure matches the old P-T chart.

Question 30

An approved retrofit changes a system from an A1 refrigerant to an A2L refrigerant. What additional issue must the technician evaluate?

A. Whether the new refrigerant automatically becomes a 500-series blend

B. Equipment design, tools, charge limits, ignition controls, and applicable safety-code requirements associated with the new flammability classification

C. Whether the original refrigerant can remain mixed in the system to reduce flammability

D. Whether the cylinder should be identified only by color

Answers and detailed explanations are provided separately in 3.10 - Answers and Explanations.md.

Topic Coverage

Review Links

After completing the practice set, review weak areas using:

• Section 3.1 - Refrigerant Properties and Phase Change
• Section 3.2 - Pure Refrigerants and Refrigerant Blends
• Section 3.3 - Temperature Glide Bubble Point and Dew Point
• Section 3.4 - Refrigerant Identification
• Section 3.5 - Refrigerant Lubricants
• Section 3.6 - Moisture Acid and Noncondensables
• Section 3.7 - Retrofitting and Substitute Refrigerants
• Section 3.8 - Quick Reference