DISTRICT OF COLOMBIA DC Master Air Conditioning and Refrigeration Mechanical Unlimited (311) Exam

DISTRICT OF COLOMBIA DC Master Air Conditioning and Refrigeration
Mechanical Unlimited (311) Exam


1. Which code serves as the basis for HVAC/R installations in Washington,
D.C.?
A) 2021 International Mechanical Code (IMC)
B) 2018 District of Columbia Construction Codes
C) 2021 International Building Code (IBC)
D) ASHRAE 90.1-2022
ANSWER: B
EXPLANATION: D.C. adopts the 2018 D.C. Construction Codes, which include
mechanical code provisions based on IMC with local amendments.
2. What is the minimum refrigerant circuit access opening size for equipment
requiring access?
A) 12 inches x 12 inches
B) 16 inches x 20 inches
C) 20 inches x 20 inches
D) 22 inches x 30 inches
ANSWER: D
EXPLANATION: IMC Section 306.5.3 requires 22" x 30" minimum for refrigerant
circuit access.
3. Which agency issues mechanical permits in Washington, D.C.?
A) D.C. Department of Consumer and Regulatory Affairs (DCRA)
B) D.C. Department of Energy and Environment (DOEE)
C) D.C. Fire and EMS Department
D) All of the above
ANSWER: A
EXPLANATION: DCRA's Construction Codes Division issues mechanical permits
in D.C.
4. What is the maximum pressure drop allowed in a natural gas piping system?
A) 0.3 inches WC
B) 0.5 inches WC
C) 1.0 inches WC
D) 3.0 inches WC
ANSWER: B
EXPLANATION: IMC Section 402.2 limits pressure drop to 0.5" WC from meter to
appliance.

,5. A Master Mechanical Unlimited license in D.C. must be renewed every:
A) 1 year
B) 2 years
C) 3 years
D) 4 years
ANSWER: B
EXPLANATION: D.C. mechanical licenses require biennial renewal.
6. What is the minimum clearance between a condensing unit and a property
line in D.C.?
A) 3 feet
B) 5 feet
C) 10 feet
D) 15 feet
ANSWER: A
EXPLANATION: D.C. Mechanical Code requires 3-foot minimum from property
lines.
7. Which of these requires a backflow preventer in D.C.?
A) Cooling tower make-up water
B) Boiler feed water
C) Chilled water systems
D) All of the above
ANSWER: D
EXPLANATION: All these systems typically require backflow prevention per D.C.
Plumbing Code.
8. What is the minimum required efficiency for new split-system air
conditioners installed in D.C.?
A) SEER 13
B) SEER 14
C) SEER 15
D) SEER 16
ANSWER: C
EXPLANATION: D.C. currently requires SEER 15 minimum for split systems.
9. A journeyman HVAC/R mechanic in D.C. must have how many years of
experience?
A) 2 years
B) 4 years
C) 5 years
D) 7 years
ANSWER: D

, EXPLANATION: D.C. requires 7 years of practical experience for journeyman
status.
10. What is the minimum clearance required in front of an air handler for
service access?
A) 18 inches
B) 24 inches
C) 30 inches
D) 36 inches
ANSWER: C
EXPLANATION: IMC requires 30-inch minimum clearance for service access.
11. Which refrigerant is being phased out under the EPA's AIM Act?
A) R-410A
B) R-134a
C) R-22
D) HFC refrigerants with high GWP
ANSWER: D
EXPLANATION: The AIM Act targets HFCs with high Global Warming Potential.
12. What is the maximum developed length for a 3-inch diameter Category I
gas vent?
A) 10 feet
B) 20 feet
C) 40 feet
D) Based on appliance input
ANSWER: D
EXPLANATION: Vent length is determined by appliance input and vent sizing
tables.
13. The D.C. Energy Conservation Code requires duct insulation with minimum
R-value of:
A) R-4
B) R-6
C) R-8
D) R-12
ANSWER: C
EXPLANATION: D.C. typically requires R-8 for duct insulation in unconditioned
spaces.
14. What is the minimum size for a combustion air opening for a 200,000 BTU
furnace?
A) 50 square inches
B) 70 square inches
C) 100 square inches