CO Refrigeration Contractor Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the main purpose of a refrigeration system?
A. To increase air pressure
B. To generate electricity
C. To remove heat from a space or substance
D. To humidify air
Rationale: Refrigeration systems are designed to remove heat from
an enclosed space or substance to maintain a lower temperature.
2. Which refrigerant is considered environmentally friendly and has zero
ozone depletion potential?
A. R-22
B. R-12
C. R-134a
D. R-502
Rationale: R-134a is a hydrofluorocarbon (HFC) refrigerant with
zero ozone depletion potential, making it safer for the environment
compared to older CFCs and HCFCs.
3. What does the term "superheat" refer to in a refrigeration system?
A. Temperature below freezing
B. Temperature of refrigerant vapor above its boiling point
C. Compressor efficiency rating
D. Liquid refrigerant temperature
Rationale: Superheat is the temperature of the refrigerant vapor
above its saturation (boiling) temperature at a given pressure.
4. What is the function of a thermostatic expansion valve (TXV)?
A. To heat the refrigerant
, B. To compress refrigerant vapor
C. To regulate the flow of refrigerant into the evaporator
D. To measure system pressure
Rationale: A TXV controls the amount of refrigerant entering the
evaporator to maintain optimal superheat and efficient cooling.
5. Which type of compressor is commonly used in small commercial
refrigeration systems?
A. Centrifugal
B. Screw
C. Reciprocating
D. Scroll
Rationale: Reciprocating compressors are widely used in small
commercial systems due to their simplicity, reliability, and cost-
effectiveness.
6. What is the purpose of an accumulator in a refrigeration system?
A. To cool the condenser
B. To prevent liquid refrigerant from entering the compressor
C. To increase system pressure
D. To filter air in the evaporator
Rationale: An accumulator captures any liquid refrigerant before it
reaches the compressor, preventing damage from liquid slugging.
7. Which component removes heat from the refrigerant and rejects it to
the atmosphere?
A. Evaporator
B. Expansion valve
C. Condenser
D. Accumulator
Rationale: The condenser allows the refrigerant to release heat to the
surrounding environment and condense from vapor to liquid.
8. What does the term "subcooling" mean?
A. Temperature above boiling point
B. Compressor inlet temperature
C. Cooling of liquid refrigerant below its saturation temperature
D. Pressure drop across the expansion valve
Rationale: Subcooling refers to cooling the liquid refrigerant below
its condensing temperature to ensure efficient operation and prevent
flashing.
, 9. In refrigeration, what is the typical function of a filter-drier?
A. Compress refrigerant
B. Remove moisture and contaminants from the refrigerant
C. Increase superheat
D. Control system pressure
Rationale: A filter-drier ensures system reliability by removing
moisture and particles that could cause corrosion or blockages.
10. What is the ideal pressure range for an R-134a system low side at
40°F evaporator temperature?
A. 20–30 psi
B. 30–40 psi
C. 50–60 psi
D. 10–20 psi
Rationale: For R-134a, the saturation pressure corresponding to
40°F is around 34 psi, making 30–40 psi the typical low-side
operating range.
11. Which safety device protects the compressor from excessive
pressure?
A. Thermostat
B. Accumulator
C. High-pressure switch
D. Expansion valve
Rationale: A high-pressure switch shuts down the system if pressure
exceeds safe limits, protecting the compressor.
12. What type of oil is typically used in refrigeration compressors
with R-134a?
A. Mineral oil
B. SAE 30 motor oil
C. Polyolester (POE) oil
D. Vegetable oil
Rationale: POE oils are compatible with HFC refrigerants like R-
134a and provide proper lubrication at operating temperatures.
13. Which law explains the relationship between pressure and boiling
point in refrigeration?
A. Ohm’s law
B. Clausius-Clapeyron equation
C. Bernoulli’s principle
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. What is the main purpose of a refrigeration system?
A. To increase air pressure
B. To generate electricity
C. To remove heat from a space or substance
D. To humidify air
Rationale: Refrigeration systems are designed to remove heat from
an enclosed space or substance to maintain a lower temperature.
2. Which refrigerant is considered environmentally friendly and has zero
ozone depletion potential?
A. R-22
B. R-12
C. R-134a
D. R-502
Rationale: R-134a is a hydrofluorocarbon (HFC) refrigerant with
zero ozone depletion potential, making it safer for the environment
compared to older CFCs and HCFCs.
3. What does the term "superheat" refer to in a refrigeration system?
A. Temperature below freezing
B. Temperature of refrigerant vapor above its boiling point
C. Compressor efficiency rating
D. Liquid refrigerant temperature
Rationale: Superheat is the temperature of the refrigerant vapor
above its saturation (boiling) temperature at a given pressure.
4. What is the function of a thermostatic expansion valve (TXV)?
A. To heat the refrigerant
, B. To compress refrigerant vapor
C. To regulate the flow of refrigerant into the evaporator
D. To measure system pressure
Rationale: A TXV controls the amount of refrigerant entering the
evaporator to maintain optimal superheat and efficient cooling.
5. Which type of compressor is commonly used in small commercial
refrigeration systems?
A. Centrifugal
B. Screw
C. Reciprocating
D. Scroll
Rationale: Reciprocating compressors are widely used in small
commercial systems due to their simplicity, reliability, and cost-
effectiveness.
6. What is the purpose of an accumulator in a refrigeration system?
A. To cool the condenser
B. To prevent liquid refrigerant from entering the compressor
C. To increase system pressure
D. To filter air in the evaporator
Rationale: An accumulator captures any liquid refrigerant before it
reaches the compressor, preventing damage from liquid slugging.
7. Which component removes heat from the refrigerant and rejects it to
the atmosphere?
A. Evaporator
B. Expansion valve
C. Condenser
D. Accumulator
Rationale: The condenser allows the refrigerant to release heat to the
surrounding environment and condense from vapor to liquid.
8. What does the term "subcooling" mean?
A. Temperature above boiling point
B. Compressor inlet temperature
C. Cooling of liquid refrigerant below its saturation temperature
D. Pressure drop across the expansion valve
Rationale: Subcooling refers to cooling the liquid refrigerant below
its condensing temperature to ensure efficient operation and prevent
flashing.
, 9. In refrigeration, what is the typical function of a filter-drier?
A. Compress refrigerant
B. Remove moisture and contaminants from the refrigerant
C. Increase superheat
D. Control system pressure
Rationale: A filter-drier ensures system reliability by removing
moisture and particles that could cause corrosion or blockages.
10. What is the ideal pressure range for an R-134a system low side at
40°F evaporator temperature?
A. 20–30 psi
B. 30–40 psi
C. 50–60 psi
D. 10–20 psi
Rationale: For R-134a, the saturation pressure corresponding to
40°F is around 34 psi, making 30–40 psi the typical low-side
operating range.
11. Which safety device protects the compressor from excessive
pressure?
A. Thermostat
B. Accumulator
C. High-pressure switch
D. Expansion valve
Rationale: A high-pressure switch shuts down the system if pressure
exceeds safe limits, protecting the compressor.
12. What type of oil is typically used in refrigeration compressors
with R-134a?
A. Mineral oil
B. SAE 30 motor oil
C. Polyolester (POE) oil
D. Vegetable oil
Rationale: POE oils are compatible with HFC refrigerants like R-
134a and provide proper lubrication at operating temperatures.
13. Which law explains the relationship between pressure and boiling
point in refrigeration?
A. Ohm’s law
B. Clausius-Clapeyron equation
C. Bernoulli’s principle
