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DC Master Air Conditioning and Refrigeration
Mechanical Unlimited (311) Exam ACTUAL
QUESTIONS AND ANSWERS LATEST UPDATE THIS
YEAR
DC Master Air Conditioning and Refrigeration Mechanical Unlimited (311) Exam, followed by 250
randomized, scenario-based MCQs with answers and summarized rationales. The questions are based
on the official exam scope, the 2012 International Mechanical Code (IMC) , OSHA 1926, the ASHRAE
Handbook, and standard HVACR principles.
✅ SUMMARIZED EXAM COVERAGE (point form)
• Regulatory & Licensing (DC-specific) – DCRA/DLCP authority, licensing pathways, eligibility
(apprentice/journeyman/master), experience requirements, exam administration by Prometric,
open-book format, approved references (2012 IMC, OSHA 1926).
• General Regulations – Permit and inspection processes, contractor responsibilities, customer
complaint handling, dispute resolution, recordkeeping, workmanship standards.
• Refrigeration Cycle & Components – Compressor, condenser, evaporator, expansion valve,
receiver, accumulator, reversing valve, superheat/subcooling, refrigeration cycle analysis
(pressure-enthalpy diagram).
• Heat Transfer & Psychrometrics – Sensible/latent heat, conduction/convection/radiation,
psychrometric chart (dry-bulb, wet-bulb, dew point, relative humidity, enthalpy),
heating/cooling load calculations.
• System Design & Installation – Duct design (friction loss, velocity, sizing), piping (refrigerant,
water, steam), equipment selection (chillers, boilers, cooling towers, heat pumps, VRF systems),
insulation, air distribution, ventilation rates (IMC Table 403.3 – 50 CFM per water closet).
• Electrical Fundamentals & Controls – AC/DC theory, motors (single-phase, three-phase, ECM),
contactors, relays, transformers, capacitors, thermostats, control wiring (24 V), safety controls
(high-pressure, low-pressure, oil pressure, freeze stats), electrical safety (lockout/tagout).
• Safety & OSHA 1926 – Electrical clearances (3 ft in front of 600 V panels), confined space entry,
fall protection, ladder safety, PPE, handling of refrigerants (recovery, recycling, reclaim), safe
brazing/welding practices.
• Refrigerants & Environmental Compliance – ASHRAE Standard 34 safety groups (A1, A2L, A3,
B1, etc.) – R-32 is A2L. EPA Section 608 (types I-IV), phasedown of high-GWP refrigerants, leak
detection, recordkeeping, proper recovery/recycling.
• Troubleshooting & Maintenance – Common system failures (compressor burnout, refrigerant
leaks, restriction, improper charge, airflow issues), oil management, winterizing, preventative
maintenance schedules.
• Energy Efficiency & Green Building – SEER, EER, HSPF, AFUE, ECM motors, variable-speed
drives, economizers, demand-controlled ventilation, LEED (where applicable), high-efficiency
equipment standards.
QUESTION 1
A master HVAC contractor is preparing to install a new 20-ton packaged rooftop unit on a commercial
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building in Washington, DC. Before beginning the installation, the contractor must first:
A) Submit a request for proposal to the building owner
B) Obtain a mechanical permit from the DC Department of Consumer and Regulatory Affairs (DCRA)
C) Notify the local fire department
D) Complete a LEED certification application
Answer: B – The DCRA is the primary regulatory body responsible for issuing permits and enforcing
building and mechanical codes in Washington, DC. A mechanical permit is required before any HVAC
work can begin.
QUESTION 2
According to OSHA 1926.403, what is the minimum required working clearance in front of a 480-volt
electrical panel?
A) 24 inches
B) 30 inches
C) 36 inches
D) 42 inches
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Answer: C – OSHA 1926.403 requires at least 3 feet of working clearance in front of electrical equipment
operating at 600 volts or less to ensure safe access and operation.
QUESTION 3
Under the 2012 International Mechanical Code (IMC), what is the minimum exhaust rate (in CFM) for a
commercial restroom that contains a water closet?
A) 25 CFM intermittent
B) 50 CFM intermittent
C) 70 CFM continuous
D) 100 CFM continuous
Answer: B – Table 403.3 of the 2012 IMC specifies 50 CFM intermittent (or 20 CFM continuous) exhaust
for each water closet in a public restroom.
QUESTION 4
Which refrigerant is classified as A2L under ASHRAE Standard 34?
A) R-22
B) R-410A
C) R-32
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D) R-134a
Answer: C – R-32 has lower flammability (A2L) and is gaining popularity as a lower-GWP alternative.
R-22 and R-410A are A1 (non-flammable), and R-134a is also A1.
QUESTION 5
A master HVAC contractor in Washington, DC is required to hold which credential to legally operate?
A) A high school diploma
B) A state-issued Master license
C) Only an apprenticeship certificate
D) A temporary work permit
Answer: B – In Washington, DC, a Master HVAC contractor must hold a state-issued Master license to
legally practice.
QUESTION 6
What is the primary purpose of a thermostat in an HVAC system?
A) To generate heat
B) To measure humidity
C) To regulate temperature by controlling heating/cooling equipment
DC Master Air Conditioning and Refrigeration
Mechanical Unlimited (311) Exam ACTUAL
QUESTIONS AND ANSWERS LATEST UPDATE THIS
YEAR
DC Master Air Conditioning and Refrigeration Mechanical Unlimited (311) Exam, followed by 250
randomized, scenario-based MCQs with answers and summarized rationales. The questions are based
on the official exam scope, the 2012 International Mechanical Code (IMC) , OSHA 1926, the ASHRAE
Handbook, and standard HVACR principles.
✅ SUMMARIZED EXAM COVERAGE (point form)
• Regulatory & Licensing (DC-specific) – DCRA/DLCP authority, licensing pathways, eligibility
(apprentice/journeyman/master), experience requirements, exam administration by Prometric,
open-book format, approved references (2012 IMC, OSHA 1926).
• General Regulations – Permit and inspection processes, contractor responsibilities, customer
complaint handling, dispute resolution, recordkeeping, workmanship standards.
• Refrigeration Cycle & Components – Compressor, condenser, evaporator, expansion valve,
receiver, accumulator, reversing valve, superheat/subcooling, refrigeration cycle analysis
(pressure-enthalpy diagram).
• Heat Transfer & Psychrometrics – Sensible/latent heat, conduction/convection/radiation,
psychrometric chart (dry-bulb, wet-bulb, dew point, relative humidity, enthalpy),
heating/cooling load calculations.
• System Design & Installation – Duct design (friction loss, velocity, sizing), piping (refrigerant,
water, steam), equipment selection (chillers, boilers, cooling towers, heat pumps, VRF systems),
insulation, air distribution, ventilation rates (IMC Table 403.3 – 50 CFM per water closet).
• Electrical Fundamentals & Controls – AC/DC theory, motors (single-phase, three-phase, ECM),
contactors, relays, transformers, capacitors, thermostats, control wiring (24 V), safety controls
(high-pressure, low-pressure, oil pressure, freeze stats), electrical safety (lockout/tagout).
• Safety & OSHA 1926 – Electrical clearances (3 ft in front of 600 V panels), confined space entry,
fall protection, ladder safety, PPE, handling of refrigerants (recovery, recycling, reclaim), safe
brazing/welding practices.
• Refrigerants & Environmental Compliance – ASHRAE Standard 34 safety groups (A1, A2L, A3,
B1, etc.) – R-32 is A2L. EPA Section 608 (types I-IV), phasedown of high-GWP refrigerants, leak
detection, recordkeeping, proper recovery/recycling.
• Troubleshooting & Maintenance – Common system failures (compressor burnout, refrigerant
leaks, restriction, improper charge, airflow issues), oil management, winterizing, preventative
maintenance schedules.
• Energy Efficiency & Green Building – SEER, EER, HSPF, AFUE, ECM motors, variable-speed
drives, economizers, demand-controlled ventilation, LEED (where applicable), high-efficiency
equipment standards.
QUESTION 1
A master HVAC contractor is preparing to install a new 20-ton packaged rooftop unit on a commercial
, Page 2 of 136
building in Washington, DC. Before beginning the installation, the contractor must first:
A) Submit a request for proposal to the building owner
B) Obtain a mechanical permit from the DC Department of Consumer and Regulatory Affairs (DCRA)
C) Notify the local fire department
D) Complete a LEED certification application
Answer: B – The DCRA is the primary regulatory body responsible for issuing permits and enforcing
building and mechanical codes in Washington, DC. A mechanical permit is required before any HVAC
work can begin.
QUESTION 2
According to OSHA 1926.403, what is the minimum required working clearance in front of a 480-volt
electrical panel?
A) 24 inches
B) 30 inches
C) 36 inches
D) 42 inches
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Answer: C – OSHA 1926.403 requires at least 3 feet of working clearance in front of electrical equipment
operating at 600 volts or less to ensure safe access and operation.
QUESTION 3
Under the 2012 International Mechanical Code (IMC), what is the minimum exhaust rate (in CFM) for a
commercial restroom that contains a water closet?
A) 25 CFM intermittent
B) 50 CFM intermittent
C) 70 CFM continuous
D) 100 CFM continuous
Answer: B – Table 403.3 of the 2012 IMC specifies 50 CFM intermittent (or 20 CFM continuous) exhaust
for each water closet in a public restroom.
QUESTION 4
Which refrigerant is classified as A2L under ASHRAE Standard 34?
A) R-22
B) R-410A
C) R-32
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D) R-134a
Answer: C – R-32 has lower flammability (A2L) and is gaining popularity as a lower-GWP alternative.
R-22 and R-410A are A1 (non-flammable), and R-134a is also A1.
QUESTION 5
A master HVAC contractor in Washington, DC is required to hold which credential to legally operate?
A) A high school diploma
B) A state-issued Master license
C) Only an apprenticeship certificate
D) A temporary work permit
Answer: B – In Washington, DC, a Master HVAC contractor must hold a state-issued Master license to
legally practice.
QUESTION 6
What is the primary purpose of a thermostat in an HVAC system?
A) To generate heat
B) To measure humidity
C) To regulate temperature by controlling heating/cooling equipment
