3.10 - Answers and Explanations

Module: Refrigerants Blends and Lubricants
Covers: All concept-check questions in Sections 3.1–3.7 and all module practice questions in Section 3.9
Total questions answered: 86
Technical and regulatory verification basis: Module 3 content current through August 7, 2026
Purpose: Provide the correct answer, explain the governing technical or service concept, address every distractor, and direct the learner to the appropriate remediation section

How to Use This File

1. Complete the relevant concept checks or the full Module 3 practice set before reading the answers.
2. Score the attempt using the answer key below.
3. Review every incorrect response.
4. Review every response marked C0 or C1, even when the selected answer was correct.
5. Enter unresolved items in the project error log.
6. Identify whether the error involved terminology, classification, a service procedure, safety, calculation/P-T interpretation, or an overgeneralized rule.
7. Explain the corrected concept without looking at this file.
8. Retest the concept later using a different question.

Mastery rule: A correct guess remains unresolved until the learner can explain why the correct answer is right and why every distractor is wrong.

Complete Module 3 Answer Key

• Section 3.1: 3.1-1: B | 3.1-2: C | 3.1-3: A | 3.1-4: D | 3.1-5: B | 3.1-6: C | 3.1-7: D | 3.1-8: A
• Section 3.2: 3.2-1: A | 3.2-2: C | 3.2-3: C | 3.2-4: B | 3.2-5: C | 3.2-6: D | 3.2-7: B | 3.2-8: C
• Section 3.3: 3.3-1: B | 3.3-2: A | 3.3-3: C | 3.3-4: B | 3.3-5: A | 3.3-6: C | 3.3-7: B | 3.3-8: D
• Section 3.4: 3.4-1: B | 3.4-2: C | 3.4-3: D | 3.4-4: B | 3.4-5: A | 3.4-6: C | 3.4-7: C | 3.4-8: A
• Section 3.5: 3.5-1: B | 3.5-2: A | 3.5-3: C | 3.5-4: B | 3.5-5: A | 3.5-6: A | 3.5-7: B | 3.5-8: C
• Section 3.6: 3.6-1: A | 3.6-2: B | 3.6-3: A | 3.6-4: C | 3.6-5: B | 3.6-6: C | 3.6-7: B | 3.6-8: C
• Section 3.7: 3.7-1: B | 3.7-2: C | 3.7-3: A | 3.7-4: D | 3.7-5: B | 3.7-6: A | 3.7-7: C | 3.7-8: D
• Section 3.9: 3.9-1: B | 3.9-2: C | 3.9-3: A | 3.9-4: D | 3.9-5: C | 3.9-6: A | 3.9-7: B | 3.9-8: D | 3.9-9: C | 3.9-10: B | 3.9-11: A | 3.9-12: D | 3.9-13: B | 3.9-14: C | 3.9-15: A | 3.9-16: D | 3.9-17: B | 3.9-18: C | 3.9-19: A | 3.9-20: D | 3.9-21: B | 3.9-22: A | 3.9-23: C | 3.9-24: D | 3.9-25: B | 3.9-26: C | 3.9-27: A | 3.9-28: D | 3.9-29: C | 3.9-30: B

Answer-File Organization

• Part A: Section 3.1 concept-check answers
• Part B: Section 3.2 concept-check answers
• Part C: Section 3.3 concept-check answers
• Part D: Section 3.4 concept-check answers
• Part E: Section 3.5 concept-check answers
• Part F: Section 3.6 concept-check answers
• Part G: Section 3.7 concept-check answers
• Part H: Section 3.9 module practice-question answers

Part A - Section 3.1 Concept-Check Answers

Source section: Section 3.1 - Refrigerant Properties and Phase Change

Answer key: B C A D B C D A

Question 3.1-1

Correct answer: B. To transfer heat by circulating and undergoing controlled thermodynamic changes

Refrigerant is the working heat-transfer fluid. It circulates through the system and absorbs or rejects heat as its pressure, temperature, and phase are controlled.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Refrigerant is the working heat-transfer fluid. It circulates through the system and absorbs or rejects heat as its pressure, temperature, and phase are controlled.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Refrigerant is the working heat-transfer fluid. It circulates through the system and absorbs or rejects heat as its pressure, temperature, and phase are controlled.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Refrigerant is the working heat-transfer fluid. It circulates through the system and absorbs or rejects heat as its pressure, temperature, and phase are controlled.

Topic: Refrigerant role

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.1-2

Correct answer: C. Heat transfer that changes temperature without changing phase

Sensible heat changes a substance’s temperature without changing its phase. During a purely sensible process, the refrigerant remains liquid or remains vapor while its temperature changes.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Sensible heat changes a substance’s temperature without changing its phase. During a purely sensible process, the refrigerant remains liquid or remains vapor while its temperature changes.

• B is incorrect: This uses an absolute or universal rule that does not apply. Sensible heat changes a substance’s temperature without changing its phase. During a purely sensible process, the refrigerant remains liquid or remains vapor while its temperature changes.

• D is incorrect: This uses an absolute or universal rule that does not apply. Sensible heat changes a substance’s temperature without changing its phase. During a purely sensible process, the refrigerant remains liquid or remains vapor while its temperature changes.

Topic: Sensible heat

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.1-3

Correct answer: A. It absorbs heat as liquid changes toward vapor.

Evaporation is the liquid-to-vapor phase change. In the evaporator, refrigerant absorbs heat from the cooled space or process as liquid refrigerant becomes vapor.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Evaporation is the liquid-to-vapor phase change. In the evaporator, refrigerant absorbs heat from the cooled space or process as liquid refrigerant becomes vapor.

• C is incorrect: This uses an absolute or universal rule that does not apply. Evaporation is the liquid-to-vapor phase change. In the evaporator, refrigerant absorbs heat from the cooled space or process as liquid refrigerant becomes vapor.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Evaporation is the liquid-to-vapor phase change. In the evaporator, refrigerant absorbs heat from the cooled space or process as liquid refrigerant becomes vapor.

Topic: Evaporation

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.1-4

Correct answer: D. Saturation temperature increases.

For a given pure refrigerant, saturation pressure and saturation temperature are linked. Increasing saturation pressure corresponds to a higher saturation temperature.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. For a given pure refrigerant, saturation pressure and saturation temperature are linked. Increasing saturation pressure corresponds to a higher saturation temperature.

• B is incorrect: This uses an absolute or universal rule that does not apply. For a given pure refrigerant, saturation pressure and saturation temperature are linked. Increasing saturation pressure corresponds to a higher saturation temperature.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. For a given pure refrigerant, saturation pressure and saturation temperature are linked. Increasing saturation pressure corresponds to a higher saturation temperature.

Topic: Saturation pressure and temperature

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.1-5

Correct answer: B. Subcooled liquid

A liquid below the saturation temperature corresponding to its pressure is subcooled liquid. It must gain sensible heat before reaching the saturated-liquid condition at that pressure.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A liquid below the saturation temperature corresponding to its pressure is subcooled liquid. It must gain sensible heat before reaching the saturated-liquid condition at that pressure.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A liquid below the saturation temperature corresponding to its pressure is subcooled liquid. It must gain sensible heat before reaching the saturated-liquid condition at that pressure.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A liquid below the saturation temperature corresponding to its pressure is subcooled liquid. It must gain sensible heat before reaching the saturated-liquid condition at that pressure.

Topic: Subcooling

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.1-6

Correct answer: C. Superheated vapor

A vapor above the saturation temperature corresponding to its pressure is superheated vapor. Its temperature exceeds the saturation temperature at that pressure.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A vapor above the saturation temperature corresponding to its pressure is superheated vapor. Its temperature exceeds the saturation temperature at that pressure.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A vapor above the saturation temperature corresponding to its pressure is superheated vapor. Its temperature exceeds the saturation temperature at that pressure.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A vapor above the saturation temperature corresponding to its pressure is superheated vapor. Its temperature exceeds the saturation temperature at that pressure.

Topic: Superheat

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.1-7

Correct answer: D. The refrigerant is at saturation, but additional information is needed to determine whether it is saturated liquid, saturated vapor, or a mixture.

At the exact saturation pressure and saturation temperature, pressure and temperature alone do not identify whether the refrigerant is saturated liquid, saturated vapor, or a two-phase mixture.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. At the exact saturation pressure and saturation temperature, pressure and temperature alone do not identify whether the refrigerant is saturated liquid, saturated vapor, or a two-phase mixture.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. At the exact saturation pressure and saturation temperature, pressure and temperature alone do not identify whether the refrigerant is saturated liquid, saturated vapor, or a two-phase mixture.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. At the exact saturation pressure and saturation temperature, pressure and temperature alone do not identify whether the refrigerant is saturated liquid, saturated vapor, or a two-phase mixture.

Topic: Saturation condition

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.1-8

Correct answer: A. It applies most directly to a pure refrigerant at essentially constant pressure; zeotropic blends can exhibit temperature glide.

A pure refrigerant changes phase at approximately constant saturation temperature when pressure is approximately constant. Zeotropic blends are an important exception because they can change temperature through the two-phase region.

• B is incorrect: This uses an absolute or universal rule that does not apply. A pure refrigerant changes phase at approximately constant saturation temperature when pressure is approximately constant. Zeotropic blends are an important exception because they can change temperature through the two-phase region.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A pure refrigerant changes phase at approximately constant saturation temperature when pressure is approximately constant. Zeotropic blends are an important exception because they can change temperature through the two-phase region.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A pure refrigerant changes phase at approximately constant saturation temperature when pressure is approximately constant. Zeotropic blends are an important exception because they can change temperature through the two-phase region.

Topic: Pure versus zeotropic phase change

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Part B - Section 3.2 Concept-Check Answers

Source section: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Answer key: A C C B C D B C

Question 3.2-1

Correct answer: A. A refrigerant made from one chemical compound

A pure refrigerant consists of one chemical compound. It is not defined by ODP, refrigerant number series, or charging method.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A pure refrigerant consists of one chemical compound. It is not defined by ODP, refrigerant number series, or charging method.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A pure refrigerant consists of one chemical compound. It is not defined by ODP, refrigerant number series, or charging method.

• D is incorrect: This uses an absolute or universal rule that does not apply. A pure refrigerant consists of one chemical compound. It is not defined by ODP, refrigerant number series, or charging method.

Topic: Pure refrigerant

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.2-2

Correct answer: C. 400 series

ASHRAE 400-series designations are generally used for zeotropic refrigerant blends. Their liquid and vapor compositions can differ, and they can exhibit temperature glide.

• A is incorrect: A pure or single-component refrigerant is not identified by the 400-series blend designation.

• B is incorrect: The 500 series is associated with azeotropic blends, not zeotropic blends.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. ASHRAE 400-series designations are generally used for zeotropic refrigerant blends. Their liquid and vapor compositions can differ, and they can exhibit temperature glide.

Topic: 400-series zeotropic blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.2-3

Correct answer: C. 500 series

ASHRAE 500-series designations are generally used for azeotropic refrigerant blends, which behave essentially like a single substance at the azeotropic composition.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. ASHRAE 500-series designations are generally used for azeotropic refrigerant blends, which behave essentially like a single substance at the azeotropic composition.

• B is incorrect: The 400 series is associated with zeotropic blends, not azeotropic blends.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. ASHRAE 500-series designations are generally used for azeotropic refrigerant blends, which behave essentially like a single substance at the azeotropic composition.

Topic: 500-series azeotropic blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.2-4

Correct answer: B. Changing blend composition because components are preferentially separated, removed, or lost

Fractionation is a change in blend composition caused by preferential separation or loss of components. It is a composition effect, not simply a temperature difference.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Fractionation is a change in blend composition caused by preferential separation or loss of components. It is a composition effect, not simply a temperature difference.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Fractionation is a change in blend composition caused by preferential separation or loss of components. It is a composition effect, not simply a temperature difference.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Fractionation is a change in blend composition caused by preferential separation or loss of components. It is a composition effect, not simply a temperature difference.

Topic: Fractionation

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.2-5

Correct answer: C. Liquid withdrawal helps preserve the specified blend composition.

A zeotropic blend is withdrawn from the supply cylinder as liquid because the liquid and vapor phases can have different compositions. Liquid withdrawal helps preserve the specified formulation.

Key distinction: Withdraw a zeotropic blend from the supply cylinder as liquid to preserve composition; then meter it safely so liquid is not slugged into a running compressor.

• A is incorrect: This uses an absolute or universal rule that does not apply. A zeotropic blend is withdrawn from the supply cylinder as liquid because the liquid and vapor phases can have different compositions. Liquid withdrawal helps preserve the specified formulation.

• B is incorrect: This uses an absolute or universal rule that does not apply. A zeotropic blend is withdrawn from the supply cylinder as liquid because the liquid and vapor phases can have different compositions. Liquid withdrawal helps preserve the specified formulation.

• D is incorrect: Liquid withdrawal preserves blend composition, but it does not authorize uncontrolled liquid entry into a running compressor.

Topic: Liquid charging of blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.2-6

Correct answer: D. It is a zeotropic blend with very small glide and remains in the 400 series.

R-410A is a near-azeotropic zeotropic blend. Its temperature glide is small, but it remains a 400-series blend rather than becoming a pure refrigerant or a 500-series azeotrope.

• A is incorrect: Near-azeotropic describes small glide; it does not change the refrigerant into a 500-series azeotrope.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. R-410A is a near-azeotropic zeotropic blend. Its temperature glide is small, but it remains a 400-series blend rather than becoming a pure refrigerant or a 500-series azeotrope.

• C is incorrect: R-410A contains more than one chemical component.

Topic: Near-azeotropic blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.2-7

Correct answer: B. Recover the complete remaining blend using the proper recovery procedure rather than intentionally separating components.

Recovery should capture the complete remaining blend. The technician does not intentionally separate blend components or attempt to recreate the formulation by adding individual components in the field.

• A is incorrect: This uses an absolute or universal rule that does not apply. Recovery should capture the complete remaining blend. The technician does not intentionally separate blend components or attempt to recreate the formulation by adding individual components in the field.

• C is incorrect: This uses an absolute or universal rule that does not apply. Recovery should capture the complete remaining blend. The technician does not intentionally separate blend components or attempt to recreate the formulation by adding individual components in the field.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Recovery should capture the complete remaining blend. The technician does not intentionally separate blend components or attempt to recreate the formulation by adding individual components in the field.

Topic: Recovery of blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.2-8

Correct answer: C. It is a 400-series zeotropic blend even though its temperature glide is very small.

R-410A’s 400-series designation identifies it as a zeotropic blend even though its glide is small. The refrigerant number alone does not state the safety classification.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. R-410A’s 400-series designation identifies it as a zeotropic blend even though its glide is small. The refrigerant number alone does not state the safety classification.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. R-410A’s 400-series designation identifies it as a zeotropic blend even though its glide is small. The refrigerant number alone does not state the safety classification.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. R-410A’s 400-series designation identifies it as a zeotropic blend even though its glide is small. The refrigerant number alone does not state the safety classification.

Topic: R-410A classification

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CLS

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Part C - Section 3.3 Concept-Check Answers

Source section: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Answer key: B A C B A C B D

Question 3.3-1

Correct answer: B. The difference between dew-point and bubble-point temperatures at the same pressure

Temperature glide is the difference between dew-point and bubble-point temperatures at the same pressure for a zeotropic blend.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Temperature glide is the difference between dew-point and bubble-point temperatures at the same pressure for a zeotropic blend.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Temperature glide is the difference between dew-point and bubble-point temperatures at the same pressure for a zeotropic blend.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Temperature glide is the difference between dew-point and bubble-point temperatures at the same pressure for a zeotropic blend.

Topic: Temperature glide

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.3-2

Correct answer: A. The saturated-liquid boundary

The bubble point is the saturated-liquid boundary. During evaporation it marks the condition at which the first bubble of vapor is associated with the saturated liquid.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The bubble point is the saturated-liquid boundary. During evaporation it marks the condition at which the first bubble of vapor is associated with the saturated liquid.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The bubble point is the saturated-liquid boundary. During evaporation it marks the condition at which the first bubble of vapor is associated with the saturated liquid.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The bubble point is the saturated-liquid boundary. During evaporation it marks the condition at which the first bubble of vapor is associated with the saturated liquid.

Topic: Bubble point

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.3-3

Correct answer: C. The saturated-vapor boundary

The dew point is the saturated-vapor boundary. During evaporation it marks the end of the two-phase region as the last liquid disappears.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The dew point is the saturated-vapor boundary. During evaporation it marks the end of the two-phase region as the last liquid disappears.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The dew point is the saturated-vapor boundary. During evaporation it marks the end of the two-phase region as the last liquid disappears.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The dew point is the saturated-vapor boundary. During evaporation it marks the end of the two-phase region as the last liquid disappears.

Topic: Dew point

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.3-4

Correct answer: B. Dew-point temperature

Superheat is referenced to the saturated-vapor condition, so the dew-point saturation temperature is normally used for a zeotropic blend.

Key distinction: Superheat → dew point.

• A is incorrect: Bubble point is the saturated-liquid reference used for subcooling, not superheat.

• C is incorrect: This uses an absolute or universal rule that does not apply. Superheat is referenced to the saturated-vapor condition, so the dew-point saturation temperature is normally used for a zeotropic blend.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Superheat is referenced to the saturated-vapor condition, so the dew-point saturation temperature is normally used for a zeotropic blend.

Topic: Superheat reference

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CAL

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.3-5

Correct answer: A. Bubble-point temperature

Subcooling is referenced to the saturated-liquid condition, so the bubble-point saturation temperature is normally used for a zeotropic blend.

Key distinction: Subcooling → bubble point.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Subcooling is referenced to the saturated-liquid condition, so the bubble-point saturation temperature is normally used for a zeotropic blend.

• C is incorrect: Dew point is the saturated-vapor reference used for superheat, not subcooling.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Subcooling is referenced to the saturated-liquid condition, so the bubble-point saturation temperature is normally used for a zeotropic blend.

Topic: Subcooling reference

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CAL

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.3-6

Correct answer: C. Bubble point → two-phase region → dew point

During evaporation at approximately constant pressure, a typical zeotropic blend moves from the bubble point through the two-phase region to the dew point.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. During evaporation at approximately constant pressure, a typical zeotropic blend moves from the bubble point through the two-phase region to the dew point.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. During evaporation at approximately constant pressure, a typical zeotropic blend moves from the bubble point through the two-phase region to the dew point.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. During evaporation at approximately constant pressure, a typical zeotropic blend moves from the bubble point through the two-phase region to the dew point.

Topic: Zeotropic evaporation

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.3-7

Correct answer: B. Glide is the bubble-to-dew temperature range, while fractionation is a change in blend composition.

Temperature glide is a temperature range during phase change at a specified pressure. Fractionation is a change in the blend’s composition. They are related to blend behavior but are not the same phenomenon.

Key distinction: Glide changes temperature through the two-phase region; fractionation changes composition.

• A is incorrect: Glide is a temperature range; fractionation is a composition change.

• C is incorrect: This uses an absolute or universal rule that does not apply. Temperature glide is a temperature range during phase change at a specified pressure. Fractionation is a change in the blend’s composition. They are related to blend behavior but are not the same phenomenon.

• D is incorrect: This uses an absolute or universal rule that does not apply. Temperature glide is a temperature range during phase change at a specified pressure. Fractionation is a change in the blend’s composition. They are related to blend behavior but are not the same phenomenon.

Topic: Glide versus fractionation

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.3-8

Correct answer: D. It is still a zeotropic blend, but its temperature glide is small.

A near-azeotropic 400-series refrigerant is still a zeotropic blend. A small glide does not make it a pure refrigerant or a 500-series azeotrope.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A near-azeotropic 400-series refrigerant is still a zeotropic blend. A small glide does not make it a pure refrigerant or a 500-series azeotrope.

• B is incorrect: This uses an absolute or universal rule that does not apply. A near-azeotropic 400-series refrigerant is still a zeotropic blend. A small glide does not make it a pure refrigerant or a 500-series azeotrope.

• C is incorrect: This uses an absolute or universal rule that does not apply. A near-azeotropic 400-series refrigerant is still a zeotropic blend. A small glide does not make it a pure refrigerant or a 500-series azeotrope.

Topic: Near-azeotropic behavior

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Part D - Section 3.4 Concept-Check Answers

Source section: Section 3.4 - Refrigerant Identification

Answer key: B C D B A C C A

Question 3.4-1

Correct answer: B. Equipment nameplate or permanent refrigerant label

The equipment nameplate or permanent refrigerant label identifies the refrigerant for which the appliance was designed, subject to any later documented retrofit.

• A is incorrect: This information does not establish the property or identification asked in the question. The equipment nameplate or permanent refrigerant label identifies the refrigerant for which the appliance was designed, subject to any later documented retrofit.

• C is incorrect: This information does not establish the property or identification asked in the question. The equipment nameplate or permanent refrigerant label identifies the refrigerant for which the appliance was designed, subject to any later documented retrofit.

• D is incorrect: This information does not establish the property or identification asked in the question. The equipment nameplate or permanent refrigerant label identifies the refrigerant for which the appliance was designed, subject to any later documented retrofit.

Topic: Equipment identification

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CLS

Review: Section 3.4 - Refrigerant Identification

Question 3.4-2

Correct answer: C. Color can be unreliable and does not prove the actual refrigerant or purity.

Cylinder color is not reliable proof of identity or purity. Cylinders can be repainted, faded, reused, or otherwise inconsistent, so the actual label and other verification information must be used.

• A is incorrect: This uses an absolute or universal rule that does not apply. Cylinder color is not reliable proof of identity or purity. Cylinders can be repainted, faded, reused, or otherwise inconsistent, so the actual label and other verification information must be used.

• B is incorrect: This uses an absolute or universal rule that does not apply. Cylinder color is not reliable proof of identity or purity. Cylinders can be repainted, faded, reused, or otherwise inconsistent, so the actual label and other verification information must be used.

• D is incorrect: This uses an absolute or universal rule that does not apply. Cylinder color is not reliable proof of identity or purity. Cylinders can be repainted, faded, reused, or otherwise inconsistent, so the actual label and other verification information must be used.

Topic: Cylinder identification

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.4 - Refrigerant Identification

Question 3.4-3

Correct answer: D. Pressure, temperature, correct refrigerant data, and suitable system condition

A meaningful P-T comparison requires both pressure and temperature, the correct refrigerant P-T data, and suitable equilibrium conditions. Pressure alone is not enough.

Key distinction: A P-T comparison is a consistency check, not proof of purity.

• A is incorrect: Pressure without temperature cannot be compared meaningfully with a refrigerant P-T relationship.

• B is incorrect: This uses an absolute or universal rule that does not apply. A meaningful P-T comparison requires both pressure and temperature, the correct refrigerant P-T data, and suitable equilibrium conditions. Pressure alone is not enough.

• C is incorrect: This information does not establish the property or identification asked in the question. A meaningful P-T comparison requires both pressure and temperature, the correct refrigerant P-T data, and suitable equilibrium conditions. Pressure alone is not enough.

Topic: P-T identification

EPA 608 section: Core

Difficulty: Applied

Suggested error code: CAL

Review: Section 3.4 - Refrigerant Identification

Question 3.4-4

Correct answer: B. Stop and investigate the refrigerant identity before mixing or charging.

If the measured static P-T behavior conflicts with the expected refrigerant, stop before charging or mixing. Recheck the measurements and identify the refrigerant, using an analyzer when necessary.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. If the measured static P-T behavior conflicts with the expected refrigerant, stop before charging or mixing. Recheck the measurements and identify the refrigerant, using an analyzer when necessary.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. If the measured static P-T behavior conflicts with the expected refrigerant, stop before charging or mixing. Recheck the measurements and identify the refrigerant, using an analyzer when necessary.

• D is incorrect: This information does not establish the property or identification asked in the question. If the measured static P-T behavior conflicts with the expected refrigerant, stop before charging or mixing. Recheck the measurements and identify the refrigerant, using an analyzer when necessary.

Topic: Conflicting identification evidence

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.4 - Refrigerant Identification

Question 3.4-5

Correct answer: A. When the refrigerant identity is unknown or contamination is suspected

A refrigerant analyzer is especially useful when refrigerant identity or purity is uncertain or contamination is suspected.

• B is incorrect: This uses an absolute or universal rule that does not apply. A refrigerant analyzer is especially useful when refrigerant identity or purity is uncertain or contamination is suspected.

• C is incorrect: This uses an absolute or universal rule that does not apply. A refrigerant analyzer is especially useful when refrigerant identity or purity is uncertain or contamination is suspected.

• D is incorrect: This uses an absolute or universal rule that does not apply. A refrigerant analyzer is especially useful when refrigerant identity or purity is uncertain or contamination is suspected.

Topic: Refrigerant analyzer

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.4 - Refrigerant Identification

Question 3.4-6

Correct answer: C. A manufactured blend has a defined formulation and published properties; an accidental mixture does not automatically have those characteristics.

A manufactured blend has a defined formulation and published properties. An accidental mixture of refrigerants does not automatically have a defined composition, designation, or predictable properties.

• A is incorrect: This uses an absolute or universal rule that does not apply. A manufactured blend has a defined formulation and published properties. An accidental mixture of refrigerants does not automatically have a defined composition, designation, or predictable properties.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A manufactured blend has a defined formulation and published properties. An accidental mixture of refrigerants does not automatically have a defined composition, designation, or predictable properties.

• D is incorrect: This uses an absolute or universal rule that does not apply. A manufactured blend has a defined formulation and published properties. An accidental mixture of refrigerants does not automatically have a defined composition, designation, or predictable properties.

Topic: Manufactured blend versus contamination

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.4 - Refrigerant Identification

Question 3.4-7

Correct answer: C. Keep the unknown refrigerant separate and identify or handle it as suspect material.

Unknown refrigerant should be kept separate from a cylinder containing known R-22. Mixing it would contaminate the known refrigerant and make later identification and handling more difficult.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Unknown refrigerant should be kept separate from a cylinder containing known R-22. Mixing it would contaminate the known refrigerant and make later identification and handling more difficult.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Unknown refrigerant should be kept separate from a cylinder containing known R-22. Mixing it would contaminate the known refrigerant and make later identification and handling more difficult.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Unknown refrigerant should be kept separate from a cylinder containing known R-22. Mixing it would contaminate the known refrigerant and make later identification and handling more difficult.

Topic: Unknown refrigerant handling

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.4 - Refrigerant Identification

Question 3.4-8

Correct answer: A. To prevent residual refrigerant in the equipment from cross-contaminating the next refrigerant

Residual refrigerant can remain in recovery machines, hoses, filters, oil, and other service equipment. Dedicated equipment or the manufacturer’s approved changeover procedure helps prevent cross-contamination.

• B is incorrect: Changing recovery equipment cannot make refrigerants share one P-T relationship.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Residual refrigerant can remain in recovery machines, hoses, filters, oil, and other service equipment. Dedicated equipment or the manufacturer’s approved changeover procedure helps prevent cross-contamination.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Residual refrigerant can remain in recovery machines, hoses, filters, oil, and other service equipment. Dedicated equipment or the manufacturer’s approved changeover procedure helps prevent cross-contamination.

Topic: Cross-contamination control

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.4 - Refrigerant Identification

Part E - Section 3.5 Concept-Check Answers

Source section: Section 3.5 - Refrigerant Lubricants

Answer key: B A C B A A B C

Question 3.5-1

Correct answer: B. Polyolester

POE is broadly associated with many HFC stationary refrigeration and air-conditioning systems. The association is useful for exam preparation, but the equipment or compressor specification controls the actual lubricant.

Key distinction: Broad HFC → POE is an exam association, not a universal field substitution rule.

• A is incorrect: Mineral oil is broadly associated with many older CFC/HCFC systems, not the common HFC association tested here.

• C is incorrect: PAO has a broad ammonia/R-717 association rather than the HFC stationary association tested here.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. POE is broadly associated with many HFC stationary refrigeration and air-conditioning systems. The association is useful for exam preparation, but the equipment or compressor specification controls the actual lubricant.

Topic: POE association

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.5-2

Correct answer: A. PAG

PAG is strongly associated with R-134a motor-vehicle air-conditioning applications. That association should not be generalized to every stationary R-134a system.

• B is incorrect: Mineral oil is not the standard broad association for R-134a MVAC systems.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. PAG is strongly associated with R-134a motor-vehicle air-conditioning applications. That association should not be generalized to every stationary R-134a system.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. PAG is strongly associated with R-134a motor-vehicle air-conditioning applications. That association should not be generalized to every stationary R-134a system.

Topic: PAG association

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.5-3

Correct answer: C. The lubricant’s resistance to flow

Viscosity is a fluid’s resistance to flow. In compressor lubrication it affects oil-film strength, circulation, and the ability of the oil to flow through bearings and passages.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Viscosity is a fluid’s resistance to flow. In compressor lubrication it affects oil-film strength, circulation, and the ability of the oil to flow through bearings and passages.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Viscosity is a fluid’s resistance to flow. In compressor lubrication it affects oil-film strength, circulation, and the ability of the oil to flow through bearings and passages.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Viscosity is a fluid’s resistance to flow. In compressor lubrication it affects oil-film strength, circulation, and the ability of the oil to flow through bearings and passages.

Topic: Viscosity

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.5-4

Correct answer: B. It affects oil circulation and return to the compressor.

Miscibility affects whether refrigerant and lubricant remain mixed over the required operating conditions and therefore influences oil circulation and return to the compressor.

• A is incorrect: This information does not establish the property or identification asked in the question. Miscibility affects whether refrigerant and lubricant remain mixed over the required operating conditions and therefore influences oil circulation and return to the compressor.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Miscibility affects whether refrigerant and lubricant remain mixed over the required operating conditions and therefore influences oil circulation and return to the compressor.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Miscibility affects whether refrigerant and lubricant remain mixed over the required operating conditions and therefore influences oil circulation and return to the compressor.

Topic: Miscibility

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.5-5

Correct answer: A. They are especially sensitive to moisture exposure.

POE and PAG are especially moisture sensitive. They should be kept sealed, clean, and dry, with exposure to ambient air minimized.

Key distinction: POE and PAG are especially hygroscopic; moisture prevention is more effective than trying to remove severe absorbed moisture later.

• B is incorrect: POE and PAG can absorb moisture; saying they cannot is the opposite of the service concern.

• C is incorrect: This uses an absolute or universal rule that does not apply. POE and PAG are especially moisture sensitive. They should be kept sealed, clean, and dry, with exposure to ambient air minimized.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. POE and PAG are especially moisture sensitive. They should be kept sealed, clean, and dry, with exposure to ambient air minimized.

Topic: Hygroscopic lubricants

EPA 608 section: Core

Difficulty: Basic

Suggested error code: SAF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.5-6

Correct answer: A. It resists electrical breakdown and supports insulation performance.

High dielectric strength means the lubricant resists electrical breakdown. This property is important in hermetic compressors where motor windings operate in the refrigerant-oil environment.

• B is incorrect: This uses an absolute or universal rule that does not apply. High dielectric strength means the lubricant resists electrical breakdown. This property is important in hermetic compressors where motor windings operate in the refrigerant-oil environment.

• C is incorrect: This uses an absolute or universal rule that does not apply. High dielectric strength means the lubricant resists electrical breakdown. This property is important in hermetic compressors where motor windings operate in the refrigerant-oil environment.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. High dielectric strength means the lubricant resists electrical breakdown. This property is important in hermetic compressors where motor windings operate in the refrigerant-oil environment.

Topic: Dielectric strength

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.5-7

Correct answer: B. The ability of the oil to resist sludge and chemical degradation caused by oxidation

Oxidation resistance is the lubricant’s ability to resist oxidation and the associated formation of sludge and degradation products.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Oxidation resistance is the lubricant’s ability to resist oxidation and the associated formation of sludge and degradation products.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Oxidation resistance is the lubricant’s ability to resist oxidation and the associated formation of sludge and degradation products.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Oxidation resistance is the lubricant’s ability to resist oxidation and the associated formation of sludge and degradation products.

Topic: Oxidation resistance

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.5-8

Correct answer: C. Verify the compressor or equipment manufacturer’s required lubricant type and viscosity grade.

A broad refrigerant-oil association is only a study aid. Before adding oil, verify the compressor or equipment manufacturer’s required lubricant chemistry, viscosity grade, and approved product.

• A is incorrect: POE is a lubricant family with different formulations and viscosity grades; not every POE is interchangeable.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A broad refrigerant-oil association is only a study aid. Before adding oil, verify the compressor or equipment manufacturer’s required lubricant chemistry, viscosity grade, and approved product.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A broad refrigerant-oil association is only a study aid. Before adding oil, verify the compressor or equipment manufacturer’s required lubricant chemistry, viscosity grade, and approved product.

Topic: Lubricant selection

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.5 - Refrigerant Lubricants

Part F - Section 3.6 Concept-Check Answers

Source section: Section 3.6 - Moisture Acid and Noncondensables

Answer key: A B A C B C B C

Question 3.6-1

Correct answer: A. Ice formation at a small refrigerant restriction

Moisture can freeze at a capillary tube, expansion-valve passage, or other small restriction and reduce or stop refrigerant flow.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Moisture can freeze at a capillary tube, expansion-valve passage, or other small restriction and reduce or stop refrigerant flow.

• C is incorrect: This uses an absolute or universal rule that does not apply. Moisture can freeze at a capillary tube, expansion-valve passage, or other small restriction and reduce or stop refrigerant flow.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Moisture can freeze at a capillary tube, expansion-valve passage, or other small restriction and reduce or stop refrigerant flow.

Topic: Moisture and ice

EPA 608 section: Core

Difficulty: Basic

Suggested error code: SAF

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.6-2

Correct answer: B. Moisture, heat, lubricant, refrigerant, and decomposition products can participate in chemical reactions that produce acidic contamination.

Acid formation depends on the refrigerant, lubricant, moisture, heat, decomposition products, and materials present. Moisture can participate in chemical degradation that produces acidic contamination.

• A is incorrect: This uses an absolute or universal rule that does not apply. Acid formation depends on the refrigerant, lubricant, moisture, heat, decomposition products, and materials present. Moisture can participate in chemical degradation that produces acidic contamination.

• C is incorrect: This uses an absolute or universal rule that does not apply. Acid formation depends on the refrigerant, lubricant, moisture, heat, decomposition products, and materials present. Moisture can participate in chemical degradation that produces acidic contamination.

• D is incorrect: This uses an absolute or universal rule that does not apply. Acid formation depends on the refrigerant, lubricant, moisture, heat, decomposition products, and materials present. Moisture can participate in chemical degradation that produces acidic contamination.

Topic: Acid formation

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.6-3

Correct answer: A. Copper deposited on compressor surfaces can interfere with clearances and lubrication.

Acidic contamination can attack copper, allowing copper to circulate and later deposit on compressor surfaces. Those deposits can interfere with clearances, bearings, and lubrication.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Acidic contamination can attack copper, allowing copper to circulate and later deposit on compressor surfaces. Those deposits can interfere with clearances, bearings, and lubrication.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Acidic contamination can attack copper, allowing copper to circulate and later deposit on compressor surfaces. Those deposits can interfere with clearances, bearings, and lubrication.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Acidic contamination can attack copper, allowing copper to circulate and later deposit on compressor surfaces. Those deposits can interfere with clearances, bearings, and lubrication.

Topic: Copper plating

EPA 608 section: Core

Difficulty: Applied

Suggested error code: SAF

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.6-4

Correct answer: C. Higher condensing or discharge pressure

Noncondensable gases such as air or residual nitrogen remain gaseous in the condenser, add to total pressure, and interfere with condenser heat transfer, commonly raising head or discharge pressure.

• A is incorrect: Noncondensables generally add pressure rather than guaranteeing a lower head pressure.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Noncondensable gases such as air or residual nitrogen remain gaseous in the condenser, add to total pressure, and interfere with condenser heat transfer, commonly raising head or discharge pressure.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Noncondensable gases such as air or residual nitrogen remain gaseous in the condenser, add to total pressure, and interfere with condenser heat transfer, commonly raising head or discharge pressure.

Topic: Noncondensables

EPA 608 section: Core

Difficulty: Applied

Suggested error code: DEF

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.6-5

Correct answer: B. To filter solid contaminants and remove moisture

A filter-drier filters solid contamination and uses a desiccant to remove moisture. Its moisture capacity is limited, so it does not replace proper evacuation.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A filter-drier filters solid contamination and uses a desiccant to remove moisture. Its moisture capacity is limited, so it does not replace proper evacuation.

• C is incorrect: This information does not establish the property or identification asked in the question. A filter-drier filters solid contamination and uses a desiccant to remove moisture. Its moisture capacity is limited, so it does not replace proper evacuation.

• D is incorrect: A filter-drier does not evacuate noncondensable gases; a vacuum procedure is needed.

Topic: Filter-driers

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.6-6

Correct answer: C. It indicates moisture condition but does not itself dry the system.

A moisture-indicating sight glass indicates the moisture condition within its design range but does not remove moisture. Its color must be interpreted according to the manufacturer’s legend.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A moisture-indicating sight glass indicates the moisture condition within its design range but does not remove moisture. Its color must be interpreted according to the manufacturer’s legend.

• B is incorrect: This uses an absolute or universal rule that does not apply. A moisture-indicating sight glass indicates the moisture condition within its design range but does not remove moisture. Its color must be interpreted according to the manufacturer’s legend.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A moisture-indicating sight glass indicates the moisture condition within its design range but does not remove moisture. Its color must be interpreted according to the manufacturer’s legend.

Topic: Moisture indicators

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.6-7

Correct answer: B. It provides much better resolution at very low absolute pressures.

A micron gauge resolves very low absolute pressures far better than a conventional compound gauge, making it the appropriate instrument for evaluating deep vacuum.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A micron gauge resolves very low absolute pressures far better than a conventional compound gauge, making it the appropriate instrument for evaluating deep vacuum.

• C is incorrect: This uses an absolute or universal rule that does not apply. A micron gauge resolves very low absolute pressures far better than a conventional compound gauge, making it the appropriate instrument for evaluating deep vacuum.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A micron gauge resolves very low absolute pressures far better than a conventional compound gauge, making it the appropriate instrument for evaluating deep vacuum.

Topic: Deep-vacuum measurement

EPA 608 section: Core

Difficulty: Applied

Suggested error code: CAL

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.6-8

Correct answer: C. Remove the nitrogen during proper evacuation so it does not remain as a noncondensable.

Nitrogen used for pressure testing must be removed during evacuation before charging. If left in the system, it becomes a noncondensable contaminant.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Nitrogen used for pressure testing must be removed during evacuation before charging. If left in the system, it becomes a noncondensable contaminant.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Nitrogen used for pressure testing must be removed during evacuation before charging. If left in the system, it becomes a noncondensable contaminant.

• D is incorrect: This information does not establish the property or identification asked in the question. Nitrogen used for pressure testing must be removed during evacuation before charging. If left in the system, it becomes a noncondensable contaminant.

Topic: Nitrogen removal

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.6 - Moisture Acid and Noncondensables

Part G - Section 3.7 Concept-Check Answers

Source section: Section 3.7 - Retrofitting and Substitute Refrigerants

Answer key: B C A D B A C D

Question 3.7-1

Correct answer: B. It is an informal term and should not replace verification of lubricant, materials, pressure, charging, and equipment compatibility.

“Drop-in replacement” is an informal term, not a universal engineering guarantee. A substitute must be checked for equipment, lubricant, materials, pressure, charging, performance, and safety compatibility.

Key distinction: Environmental acceptability, equipment compatibility, and safety/code approval are separate questions.

• A is incorrect: End-use acceptability does not guarantee that no equipment changes are required.

• C is incorrect: This uses an absolute or universal rule that does not apply. “Drop-in replacement” is an informal term, not a universal engineering guarantee. A substitute must be checked for equipment, lubricant, materials, pressure, charging, performance, and safety compatibility.

• D is incorrect: This uses an absolute or universal rule that does not apply. “Drop-in replacement” is an informal term, not a universal engineering guarantee. A substitute must be checked for equipment, lubricant, materials, pressure, charging, performance, and safety compatibility.

Topic: Drop-in misconception

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DIST

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.7-2

Correct answer: C. Whether the retrofit is compatible with the equipment, compressor, lubricant, materials, and applicable safety requirements

Acceptability for an end-use is only one part of retrofit approval. The technician must also verify compatibility with the specific equipment, compressor, lubricant, materials, pressure limits, and applicable safety requirements.

• A is incorrect: This information does not establish the property or identification asked in the question. Acceptability for an end-use is only one part of retrofit approval. The technician must also verify compatibility with the specific equipment, compressor, lubricant, materials, pressure limits, and applicable safety requirements.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Acceptability for an end-use is only one part of retrofit approval. The technician must also verify compatibility with the specific equipment, compressor, lubricant, materials, pressure limits, and applicable safety requirements.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Acceptability for an end-use is only one part of retrofit approval. The technician must also verify compatibility with the specific equipment, compressor, lubricant, materials, pressure limits, and applicable safety requirements.

Topic: Substitute selection

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CLS

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.7-3

Correct answer: A. The new refrigerant may have different miscibility, solubility, and oil-return behavior with the original lubricant.

A replacement refrigerant can have different miscibility, solubility, and oil-return behavior. The approved retrofit may therefore require a different lubricant or limits on residual original oil.

• B is incorrect: This uses an absolute or universal rule that does not apply. A replacement refrigerant can have different miscibility, solubility, and oil-return behavior. The approved retrofit may therefore require a different lubricant or limits on residual original oil.

• C is incorrect: This uses an absolute or universal rule that does not apply. A replacement refrigerant can have different miscibility, solubility, and oil-return behavior. The approved retrofit may therefore require a different lubricant or limits on residual original oil.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A replacement refrigerant can have different miscibility, solubility, and oil-return behavior. The approved retrofit may therefore require a different lubricant or limits on residual original oil.

Topic: Lubricant compatibility

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.7-4

Correct answer: D. The replacement refrigerant can have different operating pressures, and the equipment pressure rating must remain adequate.

Replacement refrigerants can operate at different suction and discharge pressures. The equipment and service components must remain within their approved pressure ratings.

• A is incorrect: This uses an absolute or universal rule that does not apply. Replacement refrigerants can operate at different suction and discharge pressures. The equipment and service components must remain within their approved pressure ratings.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Replacement refrigerants can operate at different suction and discharge pressures. The equipment and service components must remain within their approved pressure ratings.

• C is incorrect: This uses an absolute or universal rule that does not apply. Replacement refrigerants can operate at different suction and discharge pressures. The equipment and service components must remain within their approved pressure ratings.

Topic: Pressure compatibility

EPA 608 section: Core

Difficulty: Applied

Suggested error code: SAF

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.7-5

Correct answer: B. Repair leaks, pressure-test appropriately, and evacuate before final charging.

Before final charging, known leaks should be repaired, the system should be pressure-tested using the approved procedure, test gas should be removed, and the system should be properly evacuated.

• A is incorrect: Nitrogen is a test gas and must be removed before charging; leaving it creates a noncondensable.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Before final charging, known leaks should be repaired, the system should be pressure-tested using the approved procedure, test gas should be removed, and the system should be properly evacuated.

• D is incorrect: Oxygen or ordinary compressed air should not be used for refrigeration-system pressure testing because of reaction and ignition hazards.

Topic: Leak testing and evacuation

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.7-6

Correct answer: A. As liquid

A zeotropic replacement blend is normally withdrawn from the supply cylinder as liquid to preserve its specified composition.

• B is incorrect: Vapor-only withdrawal can alter the composition of a zeotropic supply cylinder.

• C is incorrect: This uses an absolute or universal rule that does not apply. A zeotropic replacement blend is normally withdrawn from the supply cylinder as liquid to preserve its specified composition.

• D is incorrect: This uses an absolute or universal rule that does not apply. A zeotropic replacement blend is normally withdrawn from the supply cylinder as liquid to preserve its specified composition.

Topic: Zeotropic retrofit charging

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.7-7

Correct answer: C. To identify the new refrigerant and relevant retrofit information so future service uses the correct refrigerant, lubricant, and P-T data

Clear retrofit labeling tells future technicians what refrigerant and relevant retrofit information now apply, reducing the risk of wrong refrigerant, lubricant, P-T data, or recovery handling.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Clear retrofit labeling tells future technicians what refrigerant and relevant retrofit information now apply, reducing the risk of wrong refrigerant, lubricant, P-T data, or recovery handling.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Clear retrofit labeling tells future technicians what refrigerant and relevant retrofit information now apply, reducing the risk of wrong refrigerant, lubricant, P-T data, or recovery handling.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Clear retrofit labeling tells future technicians what refrigerant and relevant retrofit information now apply, reducing the risk of wrong refrigerant, lubricant, P-T data, or recovery handling.

Topic: Retrofit labeling

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.7-8

Correct answer: D. A change from A1 to A2L, A2, or A3 can require different equipment, tools, charge limits, and safety procedures.

A change from A1 to A2L, A2, or A3 changes the flammability classification and can require different approved equipment, tools, charge limits, ignition controls, and code-compliant procedures.

• A is incorrect: Lower GWP does not determine flammability class.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A change from A1 to A2L, A2, or A3 changes the flammability classification and can require different approved equipment, tools, charge limits, ignition controls, and code-compliant procedures.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A change from A1 to A2L, A2, or A3 changes the flammability classification and can require different approved equipment, tools, charge limits, ignition controls, and code-compliant procedures.

Topic: Safety classification

EPA 608 section: Core

Difficulty: Applied

Suggested error code: SAF

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Part H - Section 3.9 Module Practice-Question Answers

Source section: Section 3.9 - Practice Questions

Answer key: B C A D C A B D C B A D B C A D B C A D B A C D B C A D C B

Question 3.9-1

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

Refrigerant is the system’s heat-transfer working fluid. It carries heat by circulating through controlled changes of pressure, temperature, and phase rather than by creating ‘cold energy.’

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Refrigerant is the system’s heat-transfer working fluid. It carries heat by circulating through controlled changes of pressure, temperature, and phase rather than by creating ‘cold energy.’

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Refrigerant is the system’s heat-transfer working fluid. It carries heat by circulating through controlled changes of pressure, temperature, and phase rather than by creating ‘cold energy.’

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Refrigerant is the system’s heat-transfer working fluid. It carries heat by circulating through controlled changes of pressure, temperature, and phase rather than by creating ‘cold energy.’

Topic: Refrigerant role

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.9-2

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

Latent heat is associated with phase change. During an idealized saturated phase change, heat can be absorbed or rejected without a sensible-temperature change like the one used to define sensible heat.

• A is incorrect: This uses an absolute or universal rule that does not apply. Latent heat is associated with phase change. During an idealized saturated phase change, heat can be absorbed or rejected without a sensible-temperature change like the one used to define sensible heat.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Latent heat is associated with phase change. During an idealized saturated phase change, heat can be absorbed or rejected without a sensible-temperature change like the one used to define sensible heat.

• D is incorrect: This uses an absolute or universal rule that does not apply. Latent heat is associated with phase change. During an idealized saturated phase change, heat can be absorbed or rejected without a sensible-temperature change like the one used to define sensible heat.

Topic: Latent heat

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.9-3

Correct answer: A. Saturation temperature increases.

For a given refrigerant, increasing saturation pressure corresponds to increasing saturation temperature.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. For a given refrigerant, increasing saturation pressure corresponds to increasing saturation temperature.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. For a given refrigerant, increasing saturation pressure corresponds to increasing saturation temperature.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. For a given refrigerant, increasing saturation pressure corresponds to increasing saturation temperature.

Topic: Saturation pressure and temperature

EPA 608 section: Core

Difficulty: Applied

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.9-4

Correct answer: D. Superheated

A vapor above its saturation temperature at the measured pressure is superheated vapor.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A vapor above its saturation temperature at the measured pressure is superheated vapor.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A vapor above its saturation temperature at the measured pressure is superheated vapor.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A vapor above its saturation temperature at the measured pressure is superheated vapor.

Topic: Superheat

EPA 608 section: Core

Difficulty: Applied

Suggested error code: DEF

Review: Section 3.1 - Refrigerant Properties and Phase Change

Question 3.9-5

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

A 400-series refrigerant is generally a zeotropic blend. Its components can distribute differently between liquid and vapor, leading to glide and possible fractionation.

• A is incorrect: This uses an absolute or universal rule that does not apply. A 400-series refrigerant is generally a zeotropic blend. Its components can distribute differently between liquid and vapor, leading to glide and possible fractionation.

• B is incorrect: This uses an absolute or universal rule that does not apply. A 400-series refrigerant is generally a zeotropic blend. Its components can distribute differently between liquid and vapor, leading to glide and possible fractionation.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A 400-series refrigerant is generally a zeotropic blend. Its components can distribute differently between liquid and vapor, leading to glide and possible fractionation.

Topic: 400-series zeotropic blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CLS

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.9-6

Correct answer: A. 500 series

500-series refrigerants are generally azeotropic blends.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. 500-series refrigerants are generally azeotropic blends.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. 500-series refrigerants are generally azeotropic blends.

• D is incorrect: This uses an absolute or universal rule that does not apply. 500-series refrigerants are generally azeotropic blends.

Topic: 500-series azeotropic blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CLS

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.9-7

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

A near-azeotropic blend remains zeotropic even when its glide is small. Small glide does not convert a 400-series refrigerant into a 500-series azeotrope.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A near-azeotropic blend remains zeotropic even when its glide is small. Small glide does not convert a 400-series refrigerant into a 500-series azeotrope.

• C is incorrect: A small glide does not change the 400-series zeotropic classification to 500 series.

• D is incorrect: This uses an absolute or universal rule that does not apply. A near-azeotropic blend remains zeotropic even when its glide is small. Small glide does not convert a 400-series refrigerant into a 500-series azeotrope.

Topic: Near-azeotropic behavior

EPA 608 section: Core

Difficulty: Applied

Suggested error code: CLS

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.9-8

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

Fractionation is a change in the composition of a blend caused by preferential phase separation or component loss.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Fractionation is a change in the composition of a blend caused by preferential phase separation or component loss.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Fractionation is a change in the composition of a blend caused by preferential phase separation or component loss.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Fractionation is a change in the composition of a blend caused by preferential phase separation or component loss.

Topic: Fractionation

EPA 608 section: Core

Difficulty: Applied

Suggested error code: DEF

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.9-9

Correct answer: C. Liquid withdrawal helps preserve the specified blend composition.

Zeotropic blends are normally withdrawn from the supply cylinder as liquid because liquid and vapor compositions can differ; liquid withdrawal helps preserve the specified composition.

Exam trap: Liquid withdrawal preserves blend composition; it does not mean liquid slugging is acceptable.

• A is incorrect: This uses an absolute or universal rule that does not apply. Zeotropic blends are normally withdrawn from the supply cylinder as liquid because liquid and vapor compositions can differ; liquid withdrawal helps preserve the specified composition.

• B is incorrect: This uses an absolute or universal rule that does not apply. Zeotropic blends are normally withdrawn from the supply cylinder as liquid because liquid and vapor compositions can differ; liquid withdrawal helps preserve the specified composition.

• D is incorrect: Liquid withdrawal from the cylinder does not mean uncontrolled liquid may be sent into a running compressor.

Topic: Liquid charging of blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.9-10

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

During recovery, capture the complete remaining blend rather than intentionally separating components. Recovery also does not reverse fractionation that already occurred.

• A is incorrect: This uses an absolute or universal rule that does not apply. During recovery, capture the complete remaining blend rather than intentionally separating components. Recovery also does not reverse fractionation that already occurred.

• C is incorrect: This uses an absolute or universal rule that does not apply. During recovery, capture the complete remaining blend rather than intentionally separating components. Recovery also does not reverse fractionation that already occurred.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. During recovery, capture the complete remaining blend rather than intentionally separating components. Recovery also does not reverse fractionation that already occurred.

Topic: Recovery of blends

EPA 608 section: Core

Difficulty: Basic

Suggested error code: PRO

Review: Section 3.2 - Pure Refrigerants and Refrigerant Blends

Question 3.9-11

Correct answer: A. The saturated-liquid boundary

The bubble point is the saturated-liquid boundary for a zeotropic blend.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The bubble point is the saturated-liquid boundary for a zeotropic blend.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The bubble point is the saturated-liquid boundary for a zeotropic blend.

• D is incorrect: This uses an absolute or universal rule that does not apply. The bubble point is the saturated-liquid boundary for a zeotropic blend.

Topic: Bubble point

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.9-12

Correct answer: D. The saturated-vapor boundary

The dew point is the saturated-vapor boundary for a zeotropic blend.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The dew point is the saturated-vapor boundary for a zeotropic blend.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The dew point is the saturated-vapor boundary for a zeotropic blend.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The dew point is the saturated-vapor boundary for a zeotropic blend.

Topic: Dew point

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.9-13

Correct answer: B. Dew point

Superheat is measured from the saturated-vapor reference, so use the dew-point temperature for a zeotropic blend.

Exam trap: Superheat → dew.

• A is incorrect: Bubble point is the liquid-side saturation reference used for subcooling.

• C is incorrect: This uses an absolute or universal rule that does not apply. Superheat is measured from the saturated-vapor reference, so use the dew-point temperature for a zeotropic blend.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Superheat is measured from the saturated-vapor reference, so use the dew-point temperature for a zeotropic blend.

Topic: Superheat reference

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CAL

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.9-14

Correct answer: C. Bubble point

Subcooling is measured from the saturated-liquid reference, so use the bubble-point temperature for a zeotropic blend.

Exam trap: Subcooling → bubble.

• A is incorrect: Dew point is the vapor-side saturation reference used for superheat.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Subcooling is measured from the saturated-liquid reference, so use the bubble-point temperature for a zeotropic blend.

• D is incorrect: This uses an absolute or universal rule that does not apply. Subcooling is measured from the saturated-liquid reference, so use the bubble-point temperature for a zeotropic blend.

Topic: Subcooling reference

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CAL

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.9-15

Correct answer: A. $T_{\text{dew}}-T_{\text{bubble}}$

At the same pressure, temperature glide is $T_{\text{dew}}-T_{\text{bubble}}$ for the usual bubble-to-dew convention.

• B is incorrect: This uses an absolute or universal rule that does not apply. At the same pressure, temperature glide is $T_{\text{dew}}-T_{\text{bubble}}$ for the usual bubble-to-dew convention.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. At the same pressure, temperature glide is $T_{\text{dew}}-T_{\text{bubble}}$ for the usual bubble-to-dew convention.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. At the same pressure, temperature glide is $T_{\text{dew}}-T_{\text{bubble}}$ for the usual bubble-to-dew convention.

Topic: Temperature glide

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CAL

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.9-16

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

Static pressure by itself cannot prove refrigerant identity. Pressure must be paired with temperature and other identification information because different refrigerants can show similar pressures under some conditions.

Exam trap: Pressure alone is not refrigerant identification, and even a matching P-T point does not prove purity.

• A is incorrect: Refrigerant pressure changes with temperature, so pressure alone cannot identify the fluid.

• B is incorrect: This uses an absolute or universal rule that does not apply. Static pressure by itself cannot prove refrigerant identity. Pressure must be paired with temperature and other identification information because different refrigerants can show similar pressures under some conditions.

• C is incorrect: This uses an absolute or universal rule that does not apply. Static pressure by itself cannot prove refrigerant identity. Pressure must be paired with temperature and other identification information because different refrigerants can show similar pressures under some conditions.

Topic: P-T identification limits

EPA 608 section: Core

Difficulty: Applied

Suggested error code: CAL

Review: Section 3.3 - Temperature Glide Bubble Point and Dew Point

Question 3.9-17

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

The nameplate identifies the refrigerant the equipment was designed to use, unless a documented retrofit has changed the current refrigerant.

• A is incorrect: This uses an absolute or universal rule that does not apply. The nameplate identifies the refrigerant the equipment was designed to use, unless a documented retrofit has changed the current refrigerant.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The nameplate identifies the refrigerant the equipment was designed to use, unless a documented retrofit has changed the current refrigerant.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. The nameplate identifies the refrigerant the equipment was designed to use, unless a documented retrofit has changed the current refrigerant.

Topic: Equipment nameplate

EPA 608 section: Core

Difficulty: Basic

Suggested error code: CLS

Review: Section 3.4 - Refrigerant Identification

Question 3.9-18

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

Cylinder color is not proof of refrigerant identity or purity. The label and appropriate verification methods control.

• A is incorrect: Cylinders are painted, but color is not reliable proof of refrigerant identity.

• B is incorrect: This uses an absolute or universal rule that does not apply. Cylinder color is not proof of refrigerant identity or purity. The label and appropriate verification methods control.

• D is incorrect: This uses an absolute or universal rule that does not apply. Cylinder color is not proof of refrigerant identity or purity. The label and appropriate verification methods control.

Topic: Cylinder identification

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.4 - Refrigerant Identification

Question 3.9-19

Correct answer: A. When refrigerant identity or purity is uncertain or contamination is suspected

An analyzer is especially useful when identity, purity, or possible mixed-refrigerant contamination is uncertain.

• B is incorrect: This uses an absolute or universal rule that does not apply. An analyzer is especially useful when identity, purity, or possible mixed-refrigerant contamination is uncertain.

• C is incorrect: This uses an absolute or universal rule that does not apply. An analyzer is especially useful when identity, purity, or possible mixed-refrigerant contamination is uncertain.

• D is incorrect: This uses an absolute or universal rule that does not apply. An analyzer is especially useful when identity, purity, or possible mixed-refrigerant contamination is uncertain.

Topic: Refrigerant analyzer

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.4 - Refrigerant Identification

Question 3.9-20

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

Unknown refrigerant must remain separate from a recovery cylinder containing known refrigerant. Mixing contaminates the known material.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Unknown refrigerant must remain separate from a recovery cylinder containing known refrigerant. Mixing contaminates the known material.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Unknown refrigerant must remain separate from a recovery cylinder containing known refrigerant. Mixing contaminates the known material.

• C is incorrect: This uses an absolute or universal rule that does not apply. Unknown refrigerant must remain separate from a recovery cylinder containing known refrigerant. Mixing contaminates the known material.

Topic: Mixed-refrigerant contamination

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.4 - Refrigerant Identification

Question 3.9-21

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

Many older CFC/HCFC applications used mineral oil or alkylbenzene, while many HFC stationary systems use POE. These are broad associations; the equipment specification controls actual lubricant selection.

Exam trap: MO/AB versus POE are broad associations. The equipment/compressor specification controls the actual lubricant.

• A is incorrect: This reverses the broad historical association; mineral oil was common in many older CFC/HCFC systems, not all HFC systems.

• C is incorrect: Lubricant selection depends strongly on refrigerant, compressor, and application.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Many older CFC/HCFC applications used mineral oil or alkylbenzene, while many HFC stationary systems use POE. These are broad associations; the equipment specification controls actual lubricant selection.

Topic: Lubricant compatibility

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DIST

Review: Section 3.5 - Refrigerant Lubricants

Question 3.9-22

Correct answer: A. PAG

PAG is strongly associated with R-134a MVAC applications, not with every R-134a system.

• B is incorrect: Mineral oil is not the broad lubricant association for R-134a MVAC systems.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. PAG is strongly associated with R-134a MVAC applications, not with every R-134a system.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. PAG is strongly associated with R-134a MVAC applications, not with every R-134a system.

Topic: PAG and MVAC

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.9-23

Correct answer: C. It influences oil circulation and return to the compressor.

Miscibility affects refrigerant-oil mixing behavior, circulation, and oil return to the compressor.

• A is incorrect: This information does not establish the property or identification asked in the question. Miscibility affects refrigerant-oil mixing behavior, circulation, and oil return to the compressor.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Miscibility affects refrigerant-oil mixing behavior, circulation, and oil return to the compressor.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Miscibility affects refrigerant-oil mixing behavior, circulation, and oil return to the compressor.

Topic: Miscibility

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.9-24

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

Dielectric strength is the ability of the lubricant to resist electrical breakdown, which is important around the internal motor of a hermetic compressor.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Dielectric strength is the ability of the lubricant to resist electrical breakdown, which is important around the internal motor of a hermetic compressor.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Dielectric strength is the ability of the lubricant to resist electrical breakdown, which is important around the internal motor of a hermetic compressor.

• C is incorrect: This uses an absolute or universal rule that does not apply. Dielectric strength is the ability of the lubricant to resist electrical breakdown, which is important around the internal motor of a hermetic compressor.

Topic: Dielectric strength

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.5 - Refrigerant Lubricants

Question 3.9-25

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

Moisture can cause ice at restrictions and can contribute to acid formation, corrosion, lubricant degradation, and compressor damage.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Moisture can cause ice at restrictions and can contribute to acid formation, corrosion, lubricant degradation, and compressor damage.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Moisture can cause ice at restrictions and can contribute to acid formation, corrosion, lubricant degradation, and compressor damage.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Moisture can cause ice at restrictions and can contribute to acid formation, corrosion, lubricant degradation, and compressor damage.

Topic: Moisture contamination

EPA 608 section: Core

Difficulty: Basic

Suggested error code: SAF

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.9-26

Correct answer: C. Increased head or discharge pressure and reduced condenser effectiveness

Noncondensable gases can add pressure and reduce condenser effectiveness, producing higher head or discharge pressure.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Noncondensable gases can add pressure and reduce condenser effectiveness, producing higher head or discharge pressure.

• B is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Noncondensable gases can add pressure and reduce condenser effectiveness, producing higher head or discharge pressure.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Noncondensable gases can add pressure and reduce condenser effectiveness, producing higher head or discharge pressure.

Topic: Noncondensables

EPA 608 section: Core

Difficulty: Basic

Suggested error code: DEF

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.9-27

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

A filter-drier and deep evacuation perform different jobs: the drier removes moisture and particles, while evacuation removes air, noncondensables, and water vapor.

Exam trap: Filter-drier and evacuation are complementary, not interchangeable.

• B is incorrect: A filter-drier does not remove all noncondensable gas and therefore does not eliminate the need for evacuation.

• C is incorrect: Deep evacuation removes gases and water vapor; it does not physically filter metal particles.

• D is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A filter-drier and deep evacuation perform different jobs: the drier removes moisture and particles, while evacuation removes air, noncondensables, and water vapor.

Topic: Filter-drier versus evacuation

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.6 - Moisture Acid and Noncondensables

Question 3.9-28

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

A refrigerant marketed as ‘drop-in’ still requires complete compatibility verification. Marketing language does not prove equipment, lubricant, materials, pressure, charging, or safety compatibility.

Exam trap: “Drop-in” is marketing/informal language, not a guarantee that no retrofit changes are required.

• A is incorrect: Similar pressure is not enough to establish retrofit compatibility.

• B is incorrect: This uses an absolute or universal rule that does not apply. A refrigerant marketed as ‘drop-in’ still requires complete compatibility verification. Marketing language does not prove equipment, lubricant, materials, pressure, charging, or safety compatibility.

• C is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. A refrigerant marketed as ‘drop-in’ still requires complete compatibility verification. Marketing language does not prove equipment, lubricant, materials, pressure, charging, or safety compatibility.

Topic: Drop-in misconception

EPA 608 section: Core

Difficulty: Applied

Suggested error code: DIST

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.9-29

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

Before charging a retrofit, recover the original refrigerant, complete required modifications and leak repair, pressure-test appropriately, remove the test gas, and evacuate the system.

• A is incorrect: This does not match the governing refrigerant, lubricant, contamination, or service principle. Before charging a retrofit, recover the original refrigerant, complete required modifications and leak repair, pressure-test appropriately, remove the test gas, and evacuate the system.

• B is incorrect: Nitrogen remaining in the circuit becomes a noncondensable and must be removed before charging.

• D is incorrect: A retrofit does not intentionally mix the old and new refrigerants or continue using the old refrigerant’s P-T chart.

Topic: Retrofit sequence

EPA 608 section: Core

Difficulty: Applied

Suggested error code: PRO

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

Question 3.9-30

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

Changing from A1 to A2L introduces a flammability-class change. The technician must evaluate approved equipment, tools, charge limits, ignition controls, and applicable safety-code requirements.

Exam trap: Lower GWP does not automatically mean nonflammable; A1 and A2L are different safety classifications.

• A is incorrect: Safety classification is independent of refrigerant numbering series.

• C is incorrect: Leaving the original refrigerant in the system is not an approved method for reducing flammability.

• D is incorrect: This uses an absolute or universal rule that does not apply. Changing from A1 to A2L introduces a flammability-class change. The technician must evaluate approved equipment, tools, charge limits, ignition controls, and applicable safety-code requirements.

Topic: Safety classification

EPA 608 section: Core

Difficulty: Applied

Suggested error code: SAF

Review: Section 3.7 - Retrofitting and Substitute Refrigerants

High-Priority Remediation Notes

1. Zeotropic Versus Azeotropic

Remember:

400 series → generally zeotropic
500 series → generally azeotropic

A near-azeotropic refrigerant remains a zeotropic blend even when the temperature glide is very small.

2. Temperature Glide Versus Fractionation

Glide → temperature range during two-phase change at a specified pressure
Fractionation → change in blend composition

Do not use the terms interchangeably.

3. Bubble Point and Dew Point

For a zeotropic blend:

Bubble → saturated-liquid boundary → subcooling reference
Dew    → saturated-vapor boundary → superheat reference

At the same pressure:

$$\text{Glide}=T_{\text{dew}}-T_{\text{bubble}}$$

4. Liquid Withdrawal Versus Compressor Slugging

The blend-handling rule is:

Withdraw zeotropic blend from supply cylinder as liquid

This preserves composition.

It does not mean:

Send uncontrolled liquid into a running compressor

When low-side charging is used, meter or vaporize the liquid according to the approved procedure.

5. Refrigerant Identification and P-T Data

Use:

Nameplate / retrofit label
→ cylinder label
→ service history
→ P-T consistency
→ analyzer if uncertain

Remember:

• Cylinder color alone is not identification.
• Pressure alone is not identification.
• A P-T match supports identification but does not prove purity.
• Unknown refrigerant must remain separate from known refrigerant.

6. Lubricant Associations

Broad exam associations include:

MO  → many older CFC systems
AB  → R-22 / selected applications
POE → many HFC / newer stationary systems
PAG → R-134a MVAC
PAO → R-717 / ammonia association

These are not universal substitution rules.

Actual lubricant selection depends on:

• Refrigerant.
• Compressor.
• Lubricant chemistry.
• Viscosity grade.
• Manufacturer approval.

POE and PAG are especially moisture sensitive.

7. Filter-Drier Versus Evacuation

Filter-drier → moisture + particles
Deep evacuation → air + noncondensables + water vapor

Neither process replaces the other.

8. Retrofit Decisions

There is no universal refrigerant drop-in replacement.

Before a retrofit, verify:

• End-use acceptability.
• Equipment/compressor approval.
• Pressure rating.
• Lubricant.
• Seals/materials.
• Metering device.
• Capacity.
• Safety classification.
• Applicable codes/use conditions.
• Charging and labeling procedure.

Module 3 Error-Review Checklist

For every missed or low-confidence question:

• I can define the tested term without looking.
• I can explain why the correct answer is correct.
• I can explain why all three distractors are wrong.
• I can identify the controlling condition.
• I can distinguish the concept from the nearest confusing concept.
• I reviewed the linked Module 3 section.
• I added the question to the error log if it was incorrect, C0, or C1.
• I can answer a new version of the question without notes.

References

Module 3 Instructional Sources

1. Section 3.1 - Refrigerant Properties and Phase Change

2. Section 3.2 - Pure Refrigerants and Refrigerant Blends

3. Section 3.3 - Temperature Glide Bubble Point and Dew Point

4. Section 3.4 - Refrigerant Identification

5. Section 3.5 - Refrigerant Lubricants

6. Section 3.6 - Moisture Acid and Noncondensables

7. Section 3.7 - Retrofitting and Substitute Refrigerants

8. Section 3.8 - Quick Reference

9. Section 3.9 - Practice Questions

Project Teaching and Technical References

10. International Training Institute for the Sheet Metal and Air Conditioning Industry, EPA Section 608 Study Guide, refrigerant properties, blends, lubricant, contamination, charging, and retrofit topics used as supporting teaching material.

11. Rex Miller and Mark R. Miller, HVAC Licensing Study Guide, 3rd ed., refrigerant blends, refrigerant-oil behavior, contamination, service, and retrofit topics.

12. Edward G. Pita, Air Conditioning Principles and Systems: An Energy Approach, 4th ed., refrigeration fundamentals and refrigerant/lubricant compatibility topics.

13. NCEES, PE Mechanical Reference Handbook, Version 2.0, refrigeration-property and refrigerant-table material used as a supporting engineering reference.

14. U.S. Environmental Protection Agency, Section 608 and SNAP guidance cited and verification-dated in the relevant Module 3 instructional sections.