District Of Columbia (DC)Journeyman
A/C & Refrigeration Exam 312: 312
Practice Questions & Study Guide
(2012 IMC)
Overview
The DC Journeyman A/C & Refrigeration License is a professional
credential issued by the District of Columbia Board of Industrial
Trades. It authorizes the holder to perform installation, maintenance,
and repair of air conditioning and refrigeration systems under the
supervision of a licensed Master Mechanic. This exam is designed to
ensure technicians understand the complex physics of refrigeration
cycles, electrical safety, and the legal requirements of
the International Mechanical Code (IMC).
Key Features
Open Book Policy: You are permitted to use the 2012 International
Mechanical Code and Modern Refrigeration and Air
Conditioning during the test.
Major Topics: IMC Regulations, Refrigeration Cycle Theory,
Electrical Fundamentals, Troubleshooting, and Safety.
1. According to the 2012 IMC, what is the minimum required
thickness for a galvanized steel dryer exhaust duct?
A) 0.010 inch
B) 0.013 inch
C) 0.016 inch
D) 0.020 inch
Answer: C
,Rationale: IMC Section 504.6.1 requires dryer exhaust ducts to be a
minimum of 0.016 inches thick to withstand heat and prevent lint
accumulation in ridges.
2. A "Superheat" reading that is significantly higher than the
manufacturer’s recommendation usually indicates:
A) An overcharged system.
B) A starved evaporator.
C) A dirty condenser coil.
D) Non-condensables in the system.
Answer: B
Rationale: High superheat means the refrigerant has turned into vapor
too early in the evaporator and is picking up extra sensible heat, often
due to a low charge or restricted expansion valve.
3. In a 240V single-phase motor, if you measure resistance
between one terminal and the motor shell and get 0 Ohms, the
motor is:
A) Open.
B) Shorted to ground.
C) Running normally.
D) Under-loaded.
Answer: B
Rationale: Any continuity (0 or low resistance) between the electrical
windings and the metal frame indicates a "grounded" motor, which is a
severe safety hazard.
4. What is the specific gravity of R-22 liquid compared to water?
A) 0.5
B) 1.0
C) 1.2
D) 2.4
Answer: C
Rationale: Most HCFC and HFC refrigerants are slightly denser than
water, typically ranging around 1.1 to 1.3.
5. According to IMC Section 306.5, equipment installed on a roof
must be provided with a permanent ladder if the roof is more
than _____ feet above grade.
,A) 10 feet
B) 12 feet
C) 15 feet
D) 20 feet
Answer: C
Rationale: For safety and accessibility, the code requires a permanent
means of access (ladder) for roof heights exceeding 15 feet.
6. Which component is responsible for changing low-pressure
vapor into high-pressure vapor?
A) Condenser
B) Evaporator
C) Compressor
D) Accumulator
Answer: C
Rationale: The compressor is the "heart" of the system; it creates the
pressure difference necessary for the refrigerant to flow and change
state.
7. A "Centrifugal" compressor is most commonly found in:
A) Residential window units.
B) Large commercial water chillers.
C) Household refrigerators.
D) Reach-in coolers.
Answer: B
Rationale: Centrifugal compressors are designed for high-volume,
low-pressure applications, making them ideal for large-scale industrial
cooling.
8. The 2012 IMC states that a condensate drain line must not be
smaller than _____ inch.
A) 1/2 inch
B) 3/4 inch
C) 1 inch
D) 1-1/4 inch
Answer: B
Rationale: Per IMC 307.2.1, 3/4 inch is the minimum internal diameter
required to prevent clogs from sludge and algae.
, 9. "Total Heat" in the refrigeration cycle is also known as:
A) Entropy.
B) Latent heat.
C) Enthalpy.
D) Sensible heat.
Answer: C
Rationale: Enthalpy measures the total heat content of a substance
(sensible + latent) and is used to plot the refrigeration cycle on a
Mollier chart.
10. When installing a TXV, where should the sensing bulb be
located on a 7/8" suction line?
A) Bottom of the pipe (6 o’clock position).
B) Top of the pipe (12 o’clock position).
C) Side of the pipe (4 or 8 o’clock position).
D) Inside the evaporator coil.
Answer: C
Rationale: On lines 7/8" and larger, placing the bulb at 4 or 8 o’clock
ensures it reads the temperature of the vapor and not any liquid
oil/refrigerant sitting at the bottom.
11. According to the IMC, what is the maximum length allowed
for a flexible air duct?
A) 5 feet
B) 8 feet
C) 14 feet
D) No limit
Answer: C
Rationale: IMC 603.6.1.1 restricts flexible air ducts to a maximum of
14 feet to prevent excessive friction loss and sagging.
12. A "Start Capacitor" is removed from the circuit by the:
A) Thermostat.
B) Contactor.
C) Centrifugal switch or potential relay.
D) Circuit breaker.
Answer: C
Rationale: Once the motor reaches roughly 75% of its rated speed, a
A/C & Refrigeration Exam 312: 312
Practice Questions & Study Guide
(2012 IMC)
Overview
The DC Journeyman A/C & Refrigeration License is a professional
credential issued by the District of Columbia Board of Industrial
Trades. It authorizes the holder to perform installation, maintenance,
and repair of air conditioning and refrigeration systems under the
supervision of a licensed Master Mechanic. This exam is designed to
ensure technicians understand the complex physics of refrigeration
cycles, electrical safety, and the legal requirements of
the International Mechanical Code (IMC).
Key Features
Open Book Policy: You are permitted to use the 2012 International
Mechanical Code and Modern Refrigeration and Air
Conditioning during the test.
Major Topics: IMC Regulations, Refrigeration Cycle Theory,
Electrical Fundamentals, Troubleshooting, and Safety.
1. According to the 2012 IMC, what is the minimum required
thickness for a galvanized steel dryer exhaust duct?
A) 0.010 inch
B) 0.013 inch
C) 0.016 inch
D) 0.020 inch
Answer: C
,Rationale: IMC Section 504.6.1 requires dryer exhaust ducts to be a
minimum of 0.016 inches thick to withstand heat and prevent lint
accumulation in ridges.
2. A "Superheat" reading that is significantly higher than the
manufacturer’s recommendation usually indicates:
A) An overcharged system.
B) A starved evaporator.
C) A dirty condenser coil.
D) Non-condensables in the system.
Answer: B
Rationale: High superheat means the refrigerant has turned into vapor
too early in the evaporator and is picking up extra sensible heat, often
due to a low charge or restricted expansion valve.
3. In a 240V single-phase motor, if you measure resistance
between one terminal and the motor shell and get 0 Ohms, the
motor is:
A) Open.
B) Shorted to ground.
C) Running normally.
D) Under-loaded.
Answer: B
Rationale: Any continuity (0 or low resistance) between the electrical
windings and the metal frame indicates a "grounded" motor, which is a
severe safety hazard.
4. What is the specific gravity of R-22 liquid compared to water?
A) 0.5
B) 1.0
C) 1.2
D) 2.4
Answer: C
Rationale: Most HCFC and HFC refrigerants are slightly denser than
water, typically ranging around 1.1 to 1.3.
5. According to IMC Section 306.5, equipment installed on a roof
must be provided with a permanent ladder if the roof is more
than _____ feet above grade.
,A) 10 feet
B) 12 feet
C) 15 feet
D) 20 feet
Answer: C
Rationale: For safety and accessibility, the code requires a permanent
means of access (ladder) for roof heights exceeding 15 feet.
6. Which component is responsible for changing low-pressure
vapor into high-pressure vapor?
A) Condenser
B) Evaporator
C) Compressor
D) Accumulator
Answer: C
Rationale: The compressor is the "heart" of the system; it creates the
pressure difference necessary for the refrigerant to flow and change
state.
7. A "Centrifugal" compressor is most commonly found in:
A) Residential window units.
B) Large commercial water chillers.
C) Household refrigerators.
D) Reach-in coolers.
Answer: B
Rationale: Centrifugal compressors are designed for high-volume,
low-pressure applications, making them ideal for large-scale industrial
cooling.
8. The 2012 IMC states that a condensate drain line must not be
smaller than _____ inch.
A) 1/2 inch
B) 3/4 inch
C) 1 inch
D) 1-1/4 inch
Answer: B
Rationale: Per IMC 307.2.1, 3/4 inch is the minimum internal diameter
required to prevent clogs from sludge and algae.
, 9. "Total Heat" in the refrigeration cycle is also known as:
A) Entropy.
B) Latent heat.
C) Enthalpy.
D) Sensible heat.
Answer: C
Rationale: Enthalpy measures the total heat content of a substance
(sensible + latent) and is used to plot the refrigeration cycle on a
Mollier chart.
10. When installing a TXV, where should the sensing bulb be
located on a 7/8" suction line?
A) Bottom of the pipe (6 o’clock position).
B) Top of the pipe (12 o’clock position).
C) Side of the pipe (4 or 8 o’clock position).
D) Inside the evaporator coil.
Answer: C
Rationale: On lines 7/8" and larger, placing the bulb at 4 or 8 o’clock
ensures it reads the temperature of the vapor and not any liquid
oil/refrigerant sitting at the bottom.
11. According to the IMC, what is the maximum length allowed
for a flexible air duct?
A) 5 feet
B) 8 feet
C) 14 feet
D) No limit
Answer: C
Rationale: IMC 603.6.1.1 restricts flexible air ducts to a maximum of
14 feet to prevent excessive friction loss and sagging.
12. A "Start Capacitor" is removed from the circuit by the:
A) Thermostat.
B) Contactor.
C) Centrifugal switch or potential relay.
D) Circuit breaker.
Answer: C
Rationale: Once the motor reaches roughly 75% of its rated speed, a
