Maryland HVACR Master Restricted Exam
Practice Questions and Correct Answers
(Verified Answers) Plus Rationale
Question 1
Pipe insulation shall be used to protect refrigerant piping when surface temperature
drops below ____________.
Correct Answer
Dew point
Question 2
A residential heating system has 16" galvanized duct. The minimum thickness
required by code is __________.
Correct Answer
26 gauge
Page 1 of 97
,Question 3
_____________ temperature determines the defrost termination on a heat pump using
time initiated temperature.
Correct Answer
Ambient
Question 1: In a vapor-compression refrigeration cycle, which component is
primarily responsible for rejecting heat from the refrigerant to the
surrounding air or water?
A. Evaporator
B. Compressor
C. Condenser
D. Expansion device
CORRECT ANSWER: C. Condenser
Rationale: The condenser receives high-pressure, high-temperature refrigerant
vapor from the compressor and rejects heat to the ambient medium, causing the
refrigerant to condense into a high-pressure liquid. This heat rejection is essential
for completing the refrigeration cycle.
Question 2: What is the primary function of a thermostatic expansion valve
(TXV) in an air-conditioning system?
A. To compress refrigerant vapor
B. To store excess liquid refrigerant
C. To meter refrigerant flow into the evaporator based on superheat
D. To separate oil from refrigerant
CORRECT ANSWER: C. To meter refrigerant flow into the evaporator based on
superheat
Rationale: A TXV senses evaporator outlet superheat via its sensing bulb and
modulates the orifice opening to maintain the designed superheat level, ensuring
efficient heat absorption while protecting the compressor from liquid floodback.
Question 3: According to standard refrigeration principles, what happens to
the refrigerant pressure and temperature as it passes through the expansion
Page 2 of 97
,device?
A. Both pressure and temperature increase
B. Pressure decreases and temperature increases
C. Both pressure and temperature decrease
D. Pressure increases and temperature decreases
CORRECT ANSWER: C. Both pressure and temperature decrease
Rationale: The expansion device creates a pressure drop that causes a
corresponding temperature drop through the throttling process, allowing the
refrigerant to enter the evaporator at a low temperature suitable for absorbing heat.
Question 4: Which refrigerant property is most critical when selecting oil for a
refrigeration system using HFC refrigerants?
A. Color and odor
B. Miscibility with the refrigerant
C. Electrical conductivity
D. Magnetic permeability
CORRECT ANSWER: B. Miscibility with the refrigerant
Rationale: Proper oil-refrigerant miscibility ensures oil returns to the compressor,
maintains lubrication, and prevents oil logging in the evaporator or condenser,
which is essential for long-term system reliability with HFC refrigerants.
Question 5: In an air-cooled condenser, what is the primary purpose of the
fan?
A. To increase refrigerant pressure
B. To move air across the condenser coil to enhance heat transfer
C. To circulate refrigerant through the system
D. To measure ambient temperature
CORRECT ANSWER: B. To move air across the condenser coil to enhance heat
transfer
Page 3 of 97
, Rationale: Forced airflow increases the rate of heat rejection from the condenser coil
to the ambient air, improving condenser efficiency and allowing the system to
operate at lower head pressures.
Question 6: What does the term “superheat” refer to in a refrigeration system?
A. The temperature of liquid refrigerant below its saturation temperature
B. The temperature of vapor refrigerant above its saturation temperature
C. The pressure drop across the expansion valve
D. The total heat content of the refrigerant
CORRECT ANSWER: B. The temperature of vapor refrigerant above its
saturation temperature
Rationale: Superheat is the temperature rise of refrigerant vapor beyond the
saturation temperature corresponding to the evaporator pressure, used to ensure
complete vaporization before the refrigerant reaches the compressor.
Question 7: Which component in a refrigeration system is designed to prevent
liquid refrigerant from entering the compressor?
A. Accumulator
B. Receiver
C. Oil separator
D. Filter-drier
CORRECT ANSWER: A. Accumulator
Rationale: The suction-line accumulator traps liquid refrigerant and oil, allowing
only vapor to return to the compressor while metering oil back in controlled
amounts, thereby protecting the compressor from liquid slugging.
Question 8: When recovering refrigerant from a system, what is the required
recovery level for a small appliance under EPA Section 608 regulations?
A. 0 psig
B. 4 inches of mercury vacuum
C. 10 inches of mercury vacuum
Page 4 of 97
Practice Questions and Correct Answers
(Verified Answers) Plus Rationale
Question 1
Pipe insulation shall be used to protect refrigerant piping when surface temperature
drops below ____________.
Correct Answer
Dew point
Question 2
A residential heating system has 16" galvanized duct. The minimum thickness
required by code is __________.
Correct Answer
26 gauge
Page 1 of 97
,Question 3
_____________ temperature determines the defrost termination on a heat pump using
time initiated temperature.
Correct Answer
Ambient
Question 1: In a vapor-compression refrigeration cycle, which component is
primarily responsible for rejecting heat from the refrigerant to the
surrounding air or water?
A. Evaporator
B. Compressor
C. Condenser
D. Expansion device
CORRECT ANSWER: C. Condenser
Rationale: The condenser receives high-pressure, high-temperature refrigerant
vapor from the compressor and rejects heat to the ambient medium, causing the
refrigerant to condense into a high-pressure liquid. This heat rejection is essential
for completing the refrigeration cycle.
Question 2: What is the primary function of a thermostatic expansion valve
(TXV) in an air-conditioning system?
A. To compress refrigerant vapor
B. To store excess liquid refrigerant
C. To meter refrigerant flow into the evaporator based on superheat
D. To separate oil from refrigerant
CORRECT ANSWER: C. To meter refrigerant flow into the evaporator based on
superheat
Rationale: A TXV senses evaporator outlet superheat via its sensing bulb and
modulates the orifice opening to maintain the designed superheat level, ensuring
efficient heat absorption while protecting the compressor from liquid floodback.
Question 3: According to standard refrigeration principles, what happens to
the refrigerant pressure and temperature as it passes through the expansion
Page 2 of 97
,device?
A. Both pressure and temperature increase
B. Pressure decreases and temperature increases
C. Both pressure and temperature decrease
D. Pressure increases and temperature decreases
CORRECT ANSWER: C. Both pressure and temperature decrease
Rationale: The expansion device creates a pressure drop that causes a
corresponding temperature drop through the throttling process, allowing the
refrigerant to enter the evaporator at a low temperature suitable for absorbing heat.
Question 4: Which refrigerant property is most critical when selecting oil for a
refrigeration system using HFC refrigerants?
A. Color and odor
B. Miscibility with the refrigerant
C. Electrical conductivity
D. Magnetic permeability
CORRECT ANSWER: B. Miscibility with the refrigerant
Rationale: Proper oil-refrigerant miscibility ensures oil returns to the compressor,
maintains lubrication, and prevents oil logging in the evaporator or condenser,
which is essential for long-term system reliability with HFC refrigerants.
Question 5: In an air-cooled condenser, what is the primary purpose of the
fan?
A. To increase refrigerant pressure
B. To move air across the condenser coil to enhance heat transfer
C. To circulate refrigerant through the system
D. To measure ambient temperature
CORRECT ANSWER: B. To move air across the condenser coil to enhance heat
transfer
Page 3 of 97
, Rationale: Forced airflow increases the rate of heat rejection from the condenser coil
to the ambient air, improving condenser efficiency and allowing the system to
operate at lower head pressures.
Question 6: What does the term “superheat” refer to in a refrigeration system?
A. The temperature of liquid refrigerant below its saturation temperature
B. The temperature of vapor refrigerant above its saturation temperature
C. The pressure drop across the expansion valve
D. The total heat content of the refrigerant
CORRECT ANSWER: B. The temperature of vapor refrigerant above its
saturation temperature
Rationale: Superheat is the temperature rise of refrigerant vapor beyond the
saturation temperature corresponding to the evaporator pressure, used to ensure
complete vaporization before the refrigerant reaches the compressor.
Question 7: Which component in a refrigeration system is designed to prevent
liquid refrigerant from entering the compressor?
A. Accumulator
B. Receiver
C. Oil separator
D. Filter-drier
CORRECT ANSWER: A. Accumulator
Rationale: The suction-line accumulator traps liquid refrigerant and oil, allowing
only vapor to return to the compressor while metering oil back in controlled
amounts, thereby protecting the compressor from liquid slugging.
Question 8: When recovering refrigerant from a system, what is the required
recovery level for a small appliance under EPA Section 608 regulations?
A. 0 psig
B. 4 inches of mercury vacuum
C. 10 inches of mercury vacuum
Page 4 of 97
