RETA CARO EXAM (2026/2027) Certified Assistant Refrigeration Operator
RETA CARO EXAM (2026/2027)
ACTUAL EXAM WITH COMPLETE QUESTIONS AND CORRECT ANSWERS
CERTIFIED ASSISTANT REFRIGERATION OPERATOR | REFRIGERATING ENGINEERS & TECHNICIANS
ASSOCIATION
CERTIFICATION: Certified Assistant Refrigeration Operator (CARO) Examination Preparation
EDITION: 2026/2027 | TOTAL QUESTIONS: 120 | SECTIONS: 7 | FORMAT: Multiple choice (A-D), one correct answer per
question
STANDARDS ALIGNMENT: RETA CARO Certification Blueprint and Industrial Refrigeration Core Competencies; ANSI/IIAR 1-9;
ANSI/ASHRAE 15 and 34; ASME Section VIII; OSHA 29 CFR 1910.119 (PSM), 1910.147 (LOTO), 1910.146 (Confined Space),
1910.1200 (HazCom), 1910.38 (EAP); EPA Clean Air Act Section 608 and 40 CFR 68 (RMP)
COGNITIVE LEVELS: 25% recall | 50% application | 25% analysis - including 20 calculation/diagnostic items and 10 drawing/P&ID;
interpretation items
ANSWER KEY: Every question shows the correct choice marked *[CORRECT]*, a Correct Answer line, and a rationale citing the
CARO blueprint domain and applicable industrial refrigeration standards
Section 1: Refrigeration Fundamentals & Thermodynamics Questions 1-20
Q1. Which answer correctly lists the four sequential processes of the basic single-stage vapor-compression
refrigeration cycle in operating order?
A. Evaporation, compression, condensation, expansion
B. Condensation, expansion, evaporation, compression
C. Compression, condensation, expansion, evaporation *[CORRECT]*
D. Expansion, compression, evaporation, condensation
Correct Answer: C
Rationale: Per the RETA CARO blueprint thermodynamics domain, the cycle begins at the compressor, which raises
low-pressure saturated vapor to condensing pressure and temperature. The vapor then rejects heat and condenses in the
condenser, the expansion device (hand valve, TXV, or electronic valve) drops the pressure to evaporator conditions, and
the evaporator absorbs heat as liquid boils. Options A, B, and D misplace either the compression or expansion stage and
cannot be traced as a closed loop on a standard pressure-enthalpy diagram.
Q2. On a pressure-enthalpy (P-h) diagram, the heat absorbed by refrigerant as it boils inside the evaporator is
represented by which feature?
A. A horizontal line moving to the right through the saturation (two-phase) dome at constant pressure
*[CORRECT]*
B. A vertical line moving downward, which represents isenthalpic expansion
C. A diagonal line entering the subcooled liquid region on the left of the dome
D. A short line near the critical point isobar
Correct Answer: A
Rationale: Evaporation occurs at constant pressure while enthalpy increases as latent heat is absorbed, tracing a horizontal
line through the two-phase dome on the P-h chart - a core CARO blueprint diagram-reading competency. The vertical
downward line in option B describes the expansion device, not the evaporator. The subcooled liquid region and the
critical-point area do not represent the heat-absorption process of a working evaporator.
Refrigerating Engineers & Technicians Association (RETA) 1
,RETA CARO EXAM (2026/2027) Certified Assistant Refrigeration Operator
Q3. R-717 saturation excerpt: 10 psig = -10°F, 15 psig = -1°F, 20 psig = 6°F. At the compressor inlet of an R-717
system, the suction pressure gauge reads 15 psig and the suction line temperature sensor reads 11°F. What is the
superheat?
A. 6°F
B. 8°F
C. 10°F
D. 12°F *[CORRECT]*
Correct Answer: D
Rationale: Superheat equals the actual vapor temperature minus the saturation temperature at the measured pressure: 11°F
- (-1°F) = 12°F, so option D is correct. Option C (10°F) results from using the 10 psig saturation value instead of 15 psig,
and options A and B come from subtracting gauge pressure values rather than the corresponding saturation temperature.
This is a standard CARO blueprint calculation for verifying evaporator feeding performance.
Q4. Which statement best defines subcooling in a refrigeration system?
A. The difference between the actual suction temperature and the saturation temperature at suction pressure
B. The difference between the saturation temperature at condensing pressure and the actual liquid
temperature leaving the condenser or receiver *[CORRECT]*
C. The temperature rise of refrigerant vapor through the compressor
D. The temperature difference between condenser water entering and leaving
Correct Answer: B
Rationale: Subcooling is measured on the high-pressure liquid side as the saturation temperature at condensing pressure
minus the actual liquid temperature, and it guarantees solid liquid at the expansion device with no premature flash gas.
Option A describes superheat, option C describes the heat of compression, and option D is simply the condenser water
range. The CARO blueprint requires operators to distinguish these terms because each drives a different diagnostic action.
Q5. A technician adds heat to saturated liquid ammonia in a closed test vessel while holding pressure constant.
The ammonia begins to boil, but the vessel temperature does not change. What type of heat is being added, and
why?
A. Sensible heat, because the refrigerant molecules are speeding up
B. Latent heat, because the energy is changing the phase from liquid to vapor at constant saturation
temperature *[CORRECT]*
C. Specific heat, because the vessel volume is fixed
D. Superheat, because the vapor temperature is rising
Correct Answer: B
Rationale: Heat that changes the state of a substance without changing its temperature is latent heat; here it is the latent
heat of vaporization, a foundational thermodynamics item on the CARO blueprint. Sensible heat changes temperature
without changing phase, so option A is wrong. There is no 'specific heat' phase-change mechanism as in option C, and
superheat cannot exist while liquid and vapor coexist at saturation, eliminating option D.
Refrigerating Engineers & Technicians Association (RETA) 2
,RETA CARO EXAM (2026/2027) Certified Assistant Refrigeration Operator
Q6. Why can an operator reliably convert a saturated refrigerant pressure reading into its saturation temperature
using a pressure-temperature chart?
A. Because vapor pressure rises exponentially with refrigerant mass flow
B. Because superheated vapor obeys Charles' Law at constant volume
C. Because for every saturation pressure there is exactly one corresponding saturation temperature at which
liquid and vapor coexist in equilibrium *[CORRECT]*
D. Because discharge pressure is always proportional to condenser water flow
Correct Answer: C
Rationale: In the two-phase region, pressure and temperature are rigidly coupled by the saturation curve, so a pressure
gauge plus a P-T chart is one of the operator's most powerful diagnostic tools - a key CARO blueprint skill. The chart is
valid only for saturated conditions; superheat or subcooling offsets must be applied separately. Options A, B, and D
describe relationships that are not the saturation equilibrium principle and would produce incorrect readings.
Q7. A compressor rack is producing 2,880,000 BTU/hr of refrigeration. Expressed in tons of refrigeration, the
capacity is closest to:
A. 240 tons *[CORRECT]*
B. 120 tons
C. 200 tons
D. 180 tons
Correct Answer: A
Rationale: One ton of refrigeration equals 12,000 BTU/hr, the rate required to melt one ton of ice in 24 hours, so
2,880,,000 = 240 tons, making option A correct. Option B results from dividing by 24,000, and options C and D
reflect common multiplication errors. Converting between BTU/hr and tons is a mandatory CARO blueprint calculation
used for capacity reports and load logs.
Q8. Which property represents the total heat content of a refrigerant - combining internal energy and flow work -
and is read in BTU/lb on saturation and P-h charts?
A. Entropy
B. Specific volume
C. Superheat
D. Enthalpy *[CORRECT]*
Correct Answer: D
Rationale: Enthalpy (h) is the total energy of the flowing refrigerant per unit mass, defined as internal energy plus flow
work (Pv), and it is the property read from chart scales to calculate refrigeration effect and heat of compression - a core
CARO blueprint thermodynamics term. Entropy is a different property related to energy unavailable for work, specific
volume is volume per unit mass, and superheat is a temperature difference, not an energy content.
Refrigerating Engineers & Technicians Association (RETA) 3
, RETA CARO EXAM (2026/2027) Certified Assistant Refrigeration Operator
Q9. Using a P-h diagram for an R-717 system: vapor leaving the evaporator has an enthalpy of 620 BTU/lb and
liquid entering the expansion valve has an enthalpy of 150 BTU/lb. What is the refrigeration effect?
A. 770 BTU/lb
B. 93,000 BTU/lb
C. 150 BTU/lb
D. 470 BTU/lb *[CORRECT]*
Correct Answer: D
Rationale: Refrigeration effect equals the enthalpy of vapor leaving the evaporator minus the enthalpy of liquid entering
the expansion device: 620 - 150 = 470 BTU/lb, which is option D. Option A incorrectly adds the two enthalpies, and option
C merely restates the liquid enthalpy. Refrigeration effect is the value used with the design capacity to compute refrigerant
mass flow (lb/hr = BTU/hr divided by BTU/lb), a required CARO blueprint calculation.
Q10. On a temperature-entropy (T-s) or P-h diagram, entropy is best described as the property that:
A. Equals the heat content of one pound of refrigerant
B. Remains constant during an ideal frictionless, adiabatic compression *[CORRECT]*
C. Expresses the weight of refrigerant per unit volume
D. Equals the latent heat of vaporization
Correct Answer: B
Rationale: During an ideal (isentropic) compression - frictionless and with no heat transfer - entropy stays constant, which
is why the compression stroke appears as a near-vertical line on the P-h chart and is the benchmark for compressor
efficiency comparisons in the CARO blueprint. Option A defines enthalpy, option C defines density or specific volume
relationship, and option D is the latent heat, not entropy.
Q11. In an evaporative condenser, most of the refrigerant's rejected heat is transferred to the outside air primarily
through:
A. Conduction through the coil fins alone
B. Radiation from the condensing coil surface
C. Evaporation of spray water, which carries away latent heat as a small portion of the water vaporizes
*[CORRECT]*
D. Sensible heating of the fan motor and drive belts
Correct Answer: C
Rationale: An evaporative condenser rejects heat mainly by evaporating a small fraction of the recirculated spray water;
the latent heat carried away with the vapor is far greater than the sensible heat of the air stream, which is why evaporative
units condense at temperatures much closer to the wet-bulb than air-cooled condensers. This combined
condenser-plus-cooling-tower behavior is a CARO blueprint component topic. Options A and B describe minor transfer
paths, and option D is not a heat rejection mechanism at all.
Q12. A refrigeration system delivers a refrigeration effect of 500 BTU/lb while the compressor adds 125 BTU/lb
of work. The coefficient of performance (COP) is:
A. 4.0 *[CORRECT]*
B. 0.25
C. 5.0
D. 625
Correct Answer: A
Rationale: COP is useful refrigeration divided by work input: = 4.0, so option A is correct. Option B inverts the
ratio, and option C adds instead of divides. COP links directly to horsepower per ton and to comparison against the Carnot
limit between the evaporating and condensing temperatures, a CARO blueprint energy-efficiency concept.
Refrigerating Engineers & Technicians Association (RETA) 4
RETA CARO EXAM (2026/2027)
ACTUAL EXAM WITH COMPLETE QUESTIONS AND CORRECT ANSWERS
CERTIFIED ASSISTANT REFRIGERATION OPERATOR | REFRIGERATING ENGINEERS & TECHNICIANS
ASSOCIATION
CERTIFICATION: Certified Assistant Refrigeration Operator (CARO) Examination Preparation
EDITION: 2026/2027 | TOTAL QUESTIONS: 120 | SECTIONS: 7 | FORMAT: Multiple choice (A-D), one correct answer per
question
STANDARDS ALIGNMENT: RETA CARO Certification Blueprint and Industrial Refrigeration Core Competencies; ANSI/IIAR 1-9;
ANSI/ASHRAE 15 and 34; ASME Section VIII; OSHA 29 CFR 1910.119 (PSM), 1910.147 (LOTO), 1910.146 (Confined Space),
1910.1200 (HazCom), 1910.38 (EAP); EPA Clean Air Act Section 608 and 40 CFR 68 (RMP)
COGNITIVE LEVELS: 25% recall | 50% application | 25% analysis - including 20 calculation/diagnostic items and 10 drawing/P&ID;
interpretation items
ANSWER KEY: Every question shows the correct choice marked *[CORRECT]*, a Correct Answer line, and a rationale citing the
CARO blueprint domain and applicable industrial refrigeration standards
Section 1: Refrigeration Fundamentals & Thermodynamics Questions 1-20
Q1. Which answer correctly lists the four sequential processes of the basic single-stage vapor-compression
refrigeration cycle in operating order?
A. Evaporation, compression, condensation, expansion
B. Condensation, expansion, evaporation, compression
C. Compression, condensation, expansion, evaporation *[CORRECT]*
D. Expansion, compression, evaporation, condensation
Correct Answer: C
Rationale: Per the RETA CARO blueprint thermodynamics domain, the cycle begins at the compressor, which raises
low-pressure saturated vapor to condensing pressure and temperature. The vapor then rejects heat and condenses in the
condenser, the expansion device (hand valve, TXV, or electronic valve) drops the pressure to evaporator conditions, and
the evaporator absorbs heat as liquid boils. Options A, B, and D misplace either the compression or expansion stage and
cannot be traced as a closed loop on a standard pressure-enthalpy diagram.
Q2. On a pressure-enthalpy (P-h) diagram, the heat absorbed by refrigerant as it boils inside the evaporator is
represented by which feature?
A. A horizontal line moving to the right through the saturation (two-phase) dome at constant pressure
*[CORRECT]*
B. A vertical line moving downward, which represents isenthalpic expansion
C. A diagonal line entering the subcooled liquid region on the left of the dome
D. A short line near the critical point isobar
Correct Answer: A
Rationale: Evaporation occurs at constant pressure while enthalpy increases as latent heat is absorbed, tracing a horizontal
line through the two-phase dome on the P-h chart - a core CARO blueprint diagram-reading competency. The vertical
downward line in option B describes the expansion device, not the evaporator. The subcooled liquid region and the
critical-point area do not represent the heat-absorption process of a working evaporator.
Refrigerating Engineers & Technicians Association (RETA) 1
,RETA CARO EXAM (2026/2027) Certified Assistant Refrigeration Operator
Q3. R-717 saturation excerpt: 10 psig = -10°F, 15 psig = -1°F, 20 psig = 6°F. At the compressor inlet of an R-717
system, the suction pressure gauge reads 15 psig and the suction line temperature sensor reads 11°F. What is the
superheat?
A. 6°F
B. 8°F
C. 10°F
D. 12°F *[CORRECT]*
Correct Answer: D
Rationale: Superheat equals the actual vapor temperature minus the saturation temperature at the measured pressure: 11°F
- (-1°F) = 12°F, so option D is correct. Option C (10°F) results from using the 10 psig saturation value instead of 15 psig,
and options A and B come from subtracting gauge pressure values rather than the corresponding saturation temperature.
This is a standard CARO blueprint calculation for verifying evaporator feeding performance.
Q4. Which statement best defines subcooling in a refrigeration system?
A. The difference between the actual suction temperature and the saturation temperature at suction pressure
B. The difference between the saturation temperature at condensing pressure and the actual liquid
temperature leaving the condenser or receiver *[CORRECT]*
C. The temperature rise of refrigerant vapor through the compressor
D. The temperature difference between condenser water entering and leaving
Correct Answer: B
Rationale: Subcooling is measured on the high-pressure liquid side as the saturation temperature at condensing pressure
minus the actual liquid temperature, and it guarantees solid liquid at the expansion device with no premature flash gas.
Option A describes superheat, option C describes the heat of compression, and option D is simply the condenser water
range. The CARO blueprint requires operators to distinguish these terms because each drives a different diagnostic action.
Q5. A technician adds heat to saturated liquid ammonia in a closed test vessel while holding pressure constant.
The ammonia begins to boil, but the vessel temperature does not change. What type of heat is being added, and
why?
A. Sensible heat, because the refrigerant molecules are speeding up
B. Latent heat, because the energy is changing the phase from liquid to vapor at constant saturation
temperature *[CORRECT]*
C. Specific heat, because the vessel volume is fixed
D. Superheat, because the vapor temperature is rising
Correct Answer: B
Rationale: Heat that changes the state of a substance without changing its temperature is latent heat; here it is the latent
heat of vaporization, a foundational thermodynamics item on the CARO blueprint. Sensible heat changes temperature
without changing phase, so option A is wrong. There is no 'specific heat' phase-change mechanism as in option C, and
superheat cannot exist while liquid and vapor coexist at saturation, eliminating option D.
Refrigerating Engineers & Technicians Association (RETA) 2
,RETA CARO EXAM (2026/2027) Certified Assistant Refrigeration Operator
Q6. Why can an operator reliably convert a saturated refrigerant pressure reading into its saturation temperature
using a pressure-temperature chart?
A. Because vapor pressure rises exponentially with refrigerant mass flow
B. Because superheated vapor obeys Charles' Law at constant volume
C. Because for every saturation pressure there is exactly one corresponding saturation temperature at which
liquid and vapor coexist in equilibrium *[CORRECT]*
D. Because discharge pressure is always proportional to condenser water flow
Correct Answer: C
Rationale: In the two-phase region, pressure and temperature are rigidly coupled by the saturation curve, so a pressure
gauge plus a P-T chart is one of the operator's most powerful diagnostic tools - a key CARO blueprint skill. The chart is
valid only for saturated conditions; superheat or subcooling offsets must be applied separately. Options A, B, and D
describe relationships that are not the saturation equilibrium principle and would produce incorrect readings.
Q7. A compressor rack is producing 2,880,000 BTU/hr of refrigeration. Expressed in tons of refrigeration, the
capacity is closest to:
A. 240 tons *[CORRECT]*
B. 120 tons
C. 200 tons
D. 180 tons
Correct Answer: A
Rationale: One ton of refrigeration equals 12,000 BTU/hr, the rate required to melt one ton of ice in 24 hours, so
2,880,,000 = 240 tons, making option A correct. Option B results from dividing by 24,000, and options C and D
reflect common multiplication errors. Converting between BTU/hr and tons is a mandatory CARO blueprint calculation
used for capacity reports and load logs.
Q8. Which property represents the total heat content of a refrigerant - combining internal energy and flow work -
and is read in BTU/lb on saturation and P-h charts?
A. Entropy
B. Specific volume
C. Superheat
D. Enthalpy *[CORRECT]*
Correct Answer: D
Rationale: Enthalpy (h) is the total energy of the flowing refrigerant per unit mass, defined as internal energy plus flow
work (Pv), and it is the property read from chart scales to calculate refrigeration effect and heat of compression - a core
CARO blueprint thermodynamics term. Entropy is a different property related to energy unavailable for work, specific
volume is volume per unit mass, and superheat is a temperature difference, not an energy content.
Refrigerating Engineers & Technicians Association (RETA) 3
, RETA CARO EXAM (2026/2027) Certified Assistant Refrigeration Operator
Q9. Using a P-h diagram for an R-717 system: vapor leaving the evaporator has an enthalpy of 620 BTU/lb and
liquid entering the expansion valve has an enthalpy of 150 BTU/lb. What is the refrigeration effect?
A. 770 BTU/lb
B. 93,000 BTU/lb
C. 150 BTU/lb
D. 470 BTU/lb *[CORRECT]*
Correct Answer: D
Rationale: Refrigeration effect equals the enthalpy of vapor leaving the evaporator minus the enthalpy of liquid entering
the expansion device: 620 - 150 = 470 BTU/lb, which is option D. Option A incorrectly adds the two enthalpies, and option
C merely restates the liquid enthalpy. Refrigeration effect is the value used with the design capacity to compute refrigerant
mass flow (lb/hr = BTU/hr divided by BTU/lb), a required CARO blueprint calculation.
Q10. On a temperature-entropy (T-s) or P-h diagram, entropy is best described as the property that:
A. Equals the heat content of one pound of refrigerant
B. Remains constant during an ideal frictionless, adiabatic compression *[CORRECT]*
C. Expresses the weight of refrigerant per unit volume
D. Equals the latent heat of vaporization
Correct Answer: B
Rationale: During an ideal (isentropic) compression - frictionless and with no heat transfer - entropy stays constant, which
is why the compression stroke appears as a near-vertical line on the P-h chart and is the benchmark for compressor
efficiency comparisons in the CARO blueprint. Option A defines enthalpy, option C defines density or specific volume
relationship, and option D is the latent heat, not entropy.
Q11. In an evaporative condenser, most of the refrigerant's rejected heat is transferred to the outside air primarily
through:
A. Conduction through the coil fins alone
B. Radiation from the condensing coil surface
C. Evaporation of spray water, which carries away latent heat as a small portion of the water vaporizes
*[CORRECT]*
D. Sensible heating of the fan motor and drive belts
Correct Answer: C
Rationale: An evaporative condenser rejects heat mainly by evaporating a small fraction of the recirculated spray water;
the latent heat carried away with the vapor is far greater than the sensible heat of the air stream, which is why evaporative
units condense at temperatures much closer to the wet-bulb than air-cooled condensers. This combined
condenser-plus-cooling-tower behavior is a CARO blueprint component topic. Options A and B describe minor transfer
paths, and option D is not a heat rejection mechanism at all.
Q12. A refrigeration system delivers a refrigeration effect of 500 BTU/lb while the compressor adds 125 BTU/lb
of work. The coefficient of performance (COP) is:
A. 4.0 *[CORRECT]*
B. 0.25
C. 5.0
D. 625
Correct Answer: A
Rationale: COP is useful refrigeration divided by work input: = 4.0, so option A is correct. Option B inverts the
ratio, and option C adds instead of divides. COP links directly to horsepower per ton and to comparison against the Carnot
limit between the evaporating and condensing temperatures, a CARO blueprint energy-efficiency concept.
Refrigerating Engineers & Technicians Association (RETA) 4
