FDNY HVAC Mechanical Systems
Certification Exam Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. A refrigeration mechanic discovers excessive vibration in a rooftop HVAC unit.
What is the MOST likely cause?
A. Dirty evaporator coil
B. Loose mounting bolts
C. Low refrigerant charge
D. Faulty thermostat
Answer: B. Loose mounting bolts
Rationale: Loose mounting hardware commonly causes excessive vibration in
HVAC equipment.
2. Which refrigerant safety classification indicates lower toxicity and no flame
propagation?
A. B3
B. A2L
C. A1
D. B2
Answer: C. A1
Rationale: A1 refrigerants are classified as lower toxicity and nonflammable.
,3. During inspection of an air-handling unit, a technician finds microbial growth
inside the condensate drain pan. What is the BEST corrective action?
A. Increase refrigerant pressure
B. Replace condenser fan motor
C. Clean and disinfect the drain pan
D. Lower thermostat setting
Answer: C. Clean and disinfect the drain pan
Rationale: Drain pans must be cleaned and disinfected to prevent biological
contamination.
4. A building’s HVAC system repeatedly trips the high-pressure safety control.
What condition is MOST likely present?
A. Dirty condenser coil
B. Low airflow across evaporator
C. Low refrigerant level
D. Defective humidifier
Answer: A. Dirty condenser coil
Rationale: Dirty condenser coils reduce heat rejection and increase system
pressure.
5. What is the PRIMARY function of a cooling tower in a commercial HVAC
system?
A. Increase airflow velocity
B. Reject heat from condenser water
C. Increase refrigerant pressure
D. Filter return air
Answer: B. Reject heat from condenser water
,Rationale: Cooling towers remove heat from condenser water through
evaporation.
6. Which instrument is used to measure static pressure in duct systems?
A. Hygrometer
B. Anemometer
C. Manometer
D. Psychrometer
Answer: C. Manometer
Rationale: Manometers measure pressure differences in HVAC systems.
7. A technician detects frost buildup on an evaporator coil. What is the MOST
likely cause?
A. Excess condenser airflow
B. Restricted airflow across evaporator
C. High refrigerant pressure
D. Oversized thermostat
Answer: B. Restricted airflow across evaporator
Rationale: Poor airflow can cause evaporator temperatures to drop below
freezing.
8. Which HVAC component prevents refrigerant from flowing backward?
A. Expansion valve
B. Check valve
C. Receiver
D. Sight glass
Answer: B. Check valve
Rationale: Check valves allow refrigerant flow in only one direction.
, 9. A building engineer notices low humidity levels during winter. Which HVAC
component should be inspected?
A. Humidifier
B. Economizer
C. Condenser fan
D. Expansion valve
Answer: A. Humidifier
Rationale: Humidifiers add moisture to conditioned air.
10. Which type of fire extinguisher should be used on energized HVAC electrical
equipment?
A. Class A
B. Class B
C. Class C
D. Class D
Answer: C. Class C
Rationale: Class C extinguishers are rated for energized electrical fires.
11. What is the PRIMARY purpose of an economizer cycle?
A. Increase refrigerant charge
B. Reduce electrical load using outdoor air
C. Increase humidity levels
D. Control condenser water flow
Answer: B. Reduce electrical load using outdoor air
Rationale: Economizers use cool outdoor air for energy-efficient cooling.
12. A technician measures superheat to determine:
Certification Exam Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. A refrigeration mechanic discovers excessive vibration in a rooftop HVAC unit.
What is the MOST likely cause?
A. Dirty evaporator coil
B. Loose mounting bolts
C. Low refrigerant charge
D. Faulty thermostat
Answer: B. Loose mounting bolts
Rationale: Loose mounting hardware commonly causes excessive vibration in
HVAC equipment.
2. Which refrigerant safety classification indicates lower toxicity and no flame
propagation?
A. B3
B. A2L
C. A1
D. B2
Answer: C. A1
Rationale: A1 refrigerants are classified as lower toxicity and nonflammable.
,3. During inspection of an air-handling unit, a technician finds microbial growth
inside the condensate drain pan. What is the BEST corrective action?
A. Increase refrigerant pressure
B. Replace condenser fan motor
C. Clean and disinfect the drain pan
D. Lower thermostat setting
Answer: C. Clean and disinfect the drain pan
Rationale: Drain pans must be cleaned and disinfected to prevent biological
contamination.
4. A building’s HVAC system repeatedly trips the high-pressure safety control.
What condition is MOST likely present?
A. Dirty condenser coil
B. Low airflow across evaporator
C. Low refrigerant level
D. Defective humidifier
Answer: A. Dirty condenser coil
Rationale: Dirty condenser coils reduce heat rejection and increase system
pressure.
5. What is the PRIMARY function of a cooling tower in a commercial HVAC
system?
A. Increase airflow velocity
B. Reject heat from condenser water
C. Increase refrigerant pressure
D. Filter return air
Answer: B. Reject heat from condenser water
,Rationale: Cooling towers remove heat from condenser water through
evaporation.
6. Which instrument is used to measure static pressure in duct systems?
A. Hygrometer
B. Anemometer
C. Manometer
D. Psychrometer
Answer: C. Manometer
Rationale: Manometers measure pressure differences in HVAC systems.
7. A technician detects frost buildup on an evaporator coil. What is the MOST
likely cause?
A. Excess condenser airflow
B. Restricted airflow across evaporator
C. High refrigerant pressure
D. Oversized thermostat
Answer: B. Restricted airflow across evaporator
Rationale: Poor airflow can cause evaporator temperatures to drop below
freezing.
8. Which HVAC component prevents refrigerant from flowing backward?
A. Expansion valve
B. Check valve
C. Receiver
D. Sight glass
Answer: B. Check valve
Rationale: Check valves allow refrigerant flow in only one direction.
, 9. A building engineer notices low humidity levels during winter. Which HVAC
component should be inspected?
A. Humidifier
B. Economizer
C. Condenser fan
D. Expansion valve
Answer: A. Humidifier
Rationale: Humidifiers add moisture to conditioned air.
10. Which type of fire extinguisher should be used on energized HVAC electrical
equipment?
A. Class A
B. Class B
C. Class C
D. Class D
Answer: C. Class C
Rationale: Class C extinguishers are rated for energized electrical fires.
11. What is the PRIMARY purpose of an economizer cycle?
A. Increase refrigerant charge
B. Reduce electrical load using outdoor air
C. Increase humidity levels
D. Control condenser water flow
Answer: B. Reduce electrical load using outdoor air
Rationale: Economizers use cool outdoor air for energy-efficient cooling.
12. A technician measures superheat to determine:
