1|Page
Washington D.C. Master Refrigeration and Air
Conditioning Mechanic Limited (322) Licensing
Examination | Latest Verified Questions and Detailed
Answers
OVERVIEW DESCRIPTION
This comprehensive set of multiple-choice questions is designed for the Washington
D.C. Master Refrigeration and Air Conditioning Mechanic Limited (322) Examination, an
open-book licensing assessment for professionals who install, repair, and maintain
refrigeration and air conditioning systems with a capacity of 25 compressor
horsepower or less. The content evaluates knowledge of safety regulations, local D.C.
codes, and technical proficiency across the key HVAC-R disciplines, including system
components and functionality, vapor-compression refrigeration cycles and
psychrometrics, electrical troubleshooting and motor controls, refrigerant handling
and EPA environmental requirements, OSHA and District workplace safety standards,
and proper installation and design of piping, ductwork, and insulation.
QUESTION 1
In a vapor-compression refrigeration system, the state of the refrigerant entering the
compressor should be:
A) Subcooled liquid
B) Saturated liquid
C) Superheated vapor
D) Saturated vapor
CORRECT ANSWER: C
EXPERT RATIONALE: The refrigerant must be a superheated vapor at the compressor
suction to prevent liquid slugging and damage to the compressor. Subcooled or
saturated liquid entering the compressor would cause mechanical failure.
,2|Page
QUESTION 2
Which type of compressor uses two intermeshing spiral-shaped scrolls to compress
refrigerant?
A) Reciprocating compressor
B) Screw compressor
C) Centrifugal compressor
D) Scroll compressor
CORRECT ANSWER: D
EXPERT RATIONALE: A scroll compressor captures gas between a fixed and an orbiting
scroll, progressively reducing the pocket volume to compress the refrigerant. It is
commonly used for capacities up to 25 HP.
QUESTION 3
What is the primary function of a thermostatic expansion valve (TXV)?
A) To regulate compressor oil temperature
B) To maintain a constant superheat at the evaporator outlet
C) To control condenser fan cycling
D) To equalize system pressure during off cycles
CORRECT ANSWER: B
EXPERT RATIONALE: A TXV modulates refrigerant flow to the evaporator based on the
temperature of the suction line, maintaining a preset superheat to ensure efficient
evaporator operation and prevent liquid floodback.
QUESTION 4
Which pressure-temperature relationship is used to convert gauge pressure to saturated
temperature for a specific refrigerant?
A) Dalton’s law
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B) Boyle’s law
C) A refrigerant pressure-temperature (P-T) chart
D) Charles’s law
CORRECT ANSWER: C
EXPERT RATIONALE: A P-T chart displays the saturation temperature corresponding to a
given pressure for a particular refrigerant, essential for setting and troubleshooting
system pressures.
QUESTION 5
A technician measures a suction line temperature of 45°F and a suction pressure
corresponding to 40°F saturation temperature. What is the superheat?
A) 5°F
B) 40°F
C) 45°F
D) 85°F
CORRECT ANSWER: A
EXPERT RATIONALE: Superheat is the difference between the actual suction line
temperature and the saturation temperature (45°F – 40°F = 5°F). It verifies that all liquid
has vaporized before entering the compressor.
QUESTION 6
When using a capacitor-start, induction-run motor on a compressor, which component
removes the start winding from the circuit after start-up?
A) Run capacitor
B) Potential relay
C) Current relay or centrifugal switch
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D) Crankcase heater
CORRECT ANSWER: C
EXPERT RATIONALE: A current relay or centrifugal switch disconnects the start winding
once the motor reaches about 75% of full-load speed, preventing overheating of the
auxiliary winding.
QUESTION 7
What is the maximum allowable refrigerant leak rate for comfort cooling chillers under
EPA Section 608 regulations for appliances with 50 lbs or more charge?
A) 35% per year
B) 25% per year
C) 15% per year
D) 10% per year
CORRECT ANSWER: C
EXPERT RATIONALE: EPA regulations set 15% annual leak rate threshold for comfort
cooling chillers, 35% for industrial process refrigeration, and 25% for commercial
refrigeration equipment containing 50 lbs or more.
QUESTION 8
Which device in a refrigeration system is designed to separate liquid refrigerant from
the vapor entering the compressor?
A) Receiver
B) Accumulator
C) Oil separator
D) Filter-drier
CORRECT ANSWER: B
Washington D.C. Master Refrigeration and Air
Conditioning Mechanic Limited (322) Licensing
Examination | Latest Verified Questions and Detailed
Answers
OVERVIEW DESCRIPTION
This comprehensive set of multiple-choice questions is designed for the Washington
D.C. Master Refrigeration and Air Conditioning Mechanic Limited (322) Examination, an
open-book licensing assessment for professionals who install, repair, and maintain
refrigeration and air conditioning systems with a capacity of 25 compressor
horsepower or less. The content evaluates knowledge of safety regulations, local D.C.
codes, and technical proficiency across the key HVAC-R disciplines, including system
components and functionality, vapor-compression refrigeration cycles and
psychrometrics, electrical troubleshooting and motor controls, refrigerant handling
and EPA environmental requirements, OSHA and District workplace safety standards,
and proper installation and design of piping, ductwork, and insulation.
QUESTION 1
In a vapor-compression refrigeration system, the state of the refrigerant entering the
compressor should be:
A) Subcooled liquid
B) Saturated liquid
C) Superheated vapor
D) Saturated vapor
CORRECT ANSWER: C
EXPERT RATIONALE: The refrigerant must be a superheated vapor at the compressor
suction to prevent liquid slugging and damage to the compressor. Subcooled or
saturated liquid entering the compressor would cause mechanical failure.
,2|Page
QUESTION 2
Which type of compressor uses two intermeshing spiral-shaped scrolls to compress
refrigerant?
A) Reciprocating compressor
B) Screw compressor
C) Centrifugal compressor
D) Scroll compressor
CORRECT ANSWER: D
EXPERT RATIONALE: A scroll compressor captures gas between a fixed and an orbiting
scroll, progressively reducing the pocket volume to compress the refrigerant. It is
commonly used for capacities up to 25 HP.
QUESTION 3
What is the primary function of a thermostatic expansion valve (TXV)?
A) To regulate compressor oil temperature
B) To maintain a constant superheat at the evaporator outlet
C) To control condenser fan cycling
D) To equalize system pressure during off cycles
CORRECT ANSWER: B
EXPERT RATIONALE: A TXV modulates refrigerant flow to the evaporator based on the
temperature of the suction line, maintaining a preset superheat to ensure efficient
evaporator operation and prevent liquid floodback.
QUESTION 4
Which pressure-temperature relationship is used to convert gauge pressure to saturated
temperature for a specific refrigerant?
A) Dalton’s law
,3|Page
B) Boyle’s law
C) A refrigerant pressure-temperature (P-T) chart
D) Charles’s law
CORRECT ANSWER: C
EXPERT RATIONALE: A P-T chart displays the saturation temperature corresponding to a
given pressure for a particular refrigerant, essential for setting and troubleshooting
system pressures.
QUESTION 5
A technician measures a suction line temperature of 45°F and a suction pressure
corresponding to 40°F saturation temperature. What is the superheat?
A) 5°F
B) 40°F
C) 45°F
D) 85°F
CORRECT ANSWER: A
EXPERT RATIONALE: Superheat is the difference between the actual suction line
temperature and the saturation temperature (45°F – 40°F = 5°F). It verifies that all liquid
has vaporized before entering the compressor.
QUESTION 6
When using a capacitor-start, induction-run motor on a compressor, which component
removes the start winding from the circuit after start-up?
A) Run capacitor
B) Potential relay
C) Current relay or centrifugal switch
, 4|Page
D) Crankcase heater
CORRECT ANSWER: C
EXPERT RATIONALE: A current relay or centrifugal switch disconnects the start winding
once the motor reaches about 75% of full-load speed, preventing overheating of the
auxiliary winding.
QUESTION 7
What is the maximum allowable refrigerant leak rate for comfort cooling chillers under
EPA Section 608 regulations for appliances with 50 lbs or more charge?
A) 35% per year
B) 25% per year
C) 15% per year
D) 10% per year
CORRECT ANSWER: C
EXPERT RATIONALE: EPA regulations set 15% annual leak rate threshold for comfort
cooling chillers, 35% for industrial process refrigeration, and 25% for commercial
refrigeration equipment containing 50 lbs or more.
QUESTION 8
Which device in a refrigeration system is designed to separate liquid refrigerant from
the vapor entering the compressor?
A) Receiver
B) Accumulator
C) Oil separator
D) Filter-drier
CORRECT ANSWER: B
