FDNY Refrigeration Machine Operator
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1.
A refrigeration machine operator notices that the condenser pressure on a
centrifugal chiller is steadily increasing during normal operation. What is the
MOST likely cause?
A. Low refrigerant charge
B. Dirty condenser tubes
C. Faulty thermostat
D. Open compressor windings
Answer: B. Dirty condenser tubes
Rationale: Dirty condenser tubes reduce heat transfer efficiency, causing
condenser pressure to rise during operation.
2.
Which refrigerant safety classification identifies refrigerants with 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 under
ASHRAE standards.
3.
During an inspection, an operator discovers frost forming on the suction line near
the compressor. What condition is MOST likely occurring?
A. High oil pressure
B. Floodback of liquid refrigerant
C. High condenser temperature
D. Overheated motor windings
Answer: B. Floodback of liquid refrigerant
Rationale: Frost on the suction line often indicates liquid refrigerant returning to
the compressor instead of vapor.
4.
What is the PRIMARY purpose of a purge unit on a low-pressure refrigeration
system?
A. Increase oil circulation
B. Remove non-condensable gases
C. Raise evaporator pressure
D. Add refrigerant vapor
Answer: B. Remove non-condensable gases
Rationale: Purge units remove air and other non-condensables that reduce
efficiency and increase pressure.
5.
,A machine room emergency ventilation system must activate automatically when
refrigerant vapor concentrations exceed allowable limits. This requirement
primarily protects against:
A. Compressor overheating
B. Electrical overload
C. Toxic exposure and oxygen displacement
D. Water hammer damage
Answer: C. Toxic exposure and oxygen displacement
Rationale: Refrigerant leaks can displace oxygen and create hazardous breathing
conditions.
6.
Which component prevents refrigerant from flowing backward during shutdown?
A. Expansion valve
B. Check valve
C. Oil separator
D. Solenoid coil
Answer: B. Check valve
Rationale: A check valve allows one-directional flow and prevents reverse
refrigerant movement.
7.
A reciprocating compressor repeatedly short cycles. What should the operator
check FIRST?
A. Water treatment log
B. Oil filter color
C. Low-pressure control settings
D. Cooling tower paint condition
Answer: C. Low-pressure control settings
, Rationale: Improper low-pressure control settings commonly cause short cycling.
8.
What is the function of the thermostatic expansion valve (TXV)?
A. Increase condenser temperature
B. Regulate refrigerant flow into the evaporator
C. Pump oil into the compressor
D. Control condenser fan speed
Answer: B. Regulate refrigerant flow into the evaporator
Rationale: The TXV meters refrigerant flow according to evaporator load and
superheat.
9.
A refrigeration operator observes bubbles in the sight glass during normal load
conditions. This may indicate:
A. Excess oil return
B. Refrigerant shortage
C. High chilled water flow
D. Closed discharge valve
Answer: B. Refrigerant shortage
Rationale: Bubbles in the sight glass commonly indicate low refrigerant charge or
flashing.
10.
Which device protects a compressor from dangerously high discharge pressure?
A. Flow switch
B. Pressure relief valve
Exam Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1.
A refrigeration machine operator notices that the condenser pressure on a
centrifugal chiller is steadily increasing during normal operation. What is the
MOST likely cause?
A. Low refrigerant charge
B. Dirty condenser tubes
C. Faulty thermostat
D. Open compressor windings
Answer: B. Dirty condenser tubes
Rationale: Dirty condenser tubes reduce heat transfer efficiency, causing
condenser pressure to rise during operation.
2.
Which refrigerant safety classification identifies refrigerants with 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 under
ASHRAE standards.
3.
During an inspection, an operator discovers frost forming on the suction line near
the compressor. What condition is MOST likely occurring?
A. High oil pressure
B. Floodback of liquid refrigerant
C. High condenser temperature
D. Overheated motor windings
Answer: B. Floodback of liquid refrigerant
Rationale: Frost on the suction line often indicates liquid refrigerant returning to
the compressor instead of vapor.
4.
What is the PRIMARY purpose of a purge unit on a low-pressure refrigeration
system?
A. Increase oil circulation
B. Remove non-condensable gases
C. Raise evaporator pressure
D. Add refrigerant vapor
Answer: B. Remove non-condensable gases
Rationale: Purge units remove air and other non-condensables that reduce
efficiency and increase pressure.
5.
,A machine room emergency ventilation system must activate automatically when
refrigerant vapor concentrations exceed allowable limits. This requirement
primarily protects against:
A. Compressor overheating
B. Electrical overload
C. Toxic exposure and oxygen displacement
D. Water hammer damage
Answer: C. Toxic exposure and oxygen displacement
Rationale: Refrigerant leaks can displace oxygen and create hazardous breathing
conditions.
6.
Which component prevents refrigerant from flowing backward during shutdown?
A. Expansion valve
B. Check valve
C. Oil separator
D. Solenoid coil
Answer: B. Check valve
Rationale: A check valve allows one-directional flow and prevents reverse
refrigerant movement.
7.
A reciprocating compressor repeatedly short cycles. What should the operator
check FIRST?
A. Water treatment log
B. Oil filter color
C. Low-pressure control settings
D. Cooling tower paint condition
Answer: C. Low-pressure control settings
, Rationale: Improper low-pressure control settings commonly cause short cycling.
8.
What is the function of the thermostatic expansion valve (TXV)?
A. Increase condenser temperature
B. Regulate refrigerant flow into the evaporator
C. Pump oil into the compressor
D. Control condenser fan speed
Answer: B. Regulate refrigerant flow into the evaporator
Rationale: The TXV meters refrigerant flow according to evaporator load and
superheat.
9.
A refrigeration operator observes bubbles in the sight glass during normal load
conditions. This may indicate:
A. Excess oil return
B. Refrigerant shortage
C. High chilled water flow
D. Closed discharge valve
Answer: B. Refrigerant shortage
Rationale: Bubbles in the sight glass commonly indicate low refrigerant charge or
flashing.
10.
Which device protects a compressor from dangerously high discharge pressure?
A. Flow switch
B. Pressure relief valve
