, FDNY Z-51 / Q-01 RSOE- REFRIGERATING SYSTEM OPERATING
ENGINEER EXAM | 2026 UPDATED FORMAT | QUESTIONS AND
VERIFIED ANSWERS|GRADED A+
Question 1
1. A refrigeration plant has an evaporating pressure that corresponds to 25°F saturation temperature. The measured
vapor leaving the evaporator is 38°F. What is the evaporator outlet superheat?
A. 13°F
B. 63°F
C. 25°F
D. 38°F
CORRECT ANSWER
A. 13°F
Explanation: Superheat is actual vapor temperature minus saturation temperature: 38 − 25 = 13°F.
Question 2
2. When refrigerant pressure increases during compression, the saturation temperature generally:
A. Decreases
B. Increases
C. Becomes zero
D. Is unaffected by pressure
CORRECT ANSWER
B. Increases
Explanation: For a given refrigerant, saturation temperature generally rises as pressure rises.
Question 3
3. A compressor suction line carries refrigerant that should normally be:
A. High-pressure liquid
B. Low-pressure vapor
C. High-pressure vapor
D. Low-pressure liquid only
CORRECT ANSWER
B. Low-pressure vapor
Explanation: The suction line returns low-pressure refrigerant vapor from the evaporator toward the compressor.
,1 FDNY Z-51 / Q-01 PRACTICE EXAM
,Question 4
4. The main purpose of the condenser fan on an air-cooled condenser is to:
A. Increase refrigerant charge
B. Move air across the heat-transfer surface
C. Meter liquid refrigerant
D. Lubricate the compressor
CORRECT ANSWER
B. Move air across the heat-transfer surface
Explanation: The fan increases airflow across the condenser so heat can be rejected to the surrounding air.
Question 5
5. If the evaporator load increases while other conditions remain suitable, the refrigeration system willgenerally
need to:
A. Transfer more heat through the evaporator
B. Stop refrigerant circulation
C. Eliminate the compressor
D. Remove the condenser
CORRECT ANSWER
A. Transfer more heat through the evaporator
Explanation: A higher cooling load requires the evaporator to absorb more heat, with the system responding through
refrigerant flow and compressor capacity.
Question 6
6. A refrigeration cycle is best described as a process that:
A. Moves heat from a lower-temperature region to a higher-temperature heat sink using work
B. Creates heat from nothing
C. Destroys refrigerant
D. Moves heat only by natural convection
CORRECT ANSWER
A. Moves heat from a lower-temperature region to a higher-temperature heat sink using work
Explanation: Refrigeration uses work, normally compressor work, to transfer heat from a colder region to a warmer sink.
,2 FDNY Z-51 / Q-01 PRACTICE EXAM
,Question 7
7. Which condition is most directly associated with saturated liquid?
A. Liquid at its saturation condition before further sensible cooling
B. Vapor above saturation temperature
C. Superheated vapor
D. Compressed air
CORRECT ANSWER
A. Liquid at its saturation condition before further sensible cooling
Explanation: Saturated liquid is liquid at the saturation condition for its pressure; further cooling produces subcooling.
Question 8
8. Why is pressure-temperature information important to an operator?
A. It helps relate measured pressure to refrigerant saturation conditions
B. It eliminates the need for thermometers
C. It determines building occupancy
D. It replaces electrical testing
CORRECT ANSWER
A. It helps relate measured pressure to refrigerant saturation conditions
Explanation: Pressure-temperature relationships allow an operator to compare measured pressures with saturation
temperatures and evaluate superheat/subcooling.
Question 9
9. A reciprocating compressor's suction valve opens primarily when:
A. Cylinder conditions permit vapor to enter during the suction stroke
B. The condenser is full of liquid
C. The receiver is empty
D. The motor is disconnected
CORRECT ANSWER
A. Cylinder conditions permit vapor to enter during the suction stroke
Explanation: The suction valve admits low-pressure vapor into the cylinder during the appropriate part of the compressor
cycle.
, 3 FDNY Z-51 / Q-01 PRACTICE EXAM
ENGINEER EXAM | 2026 UPDATED FORMAT | QUESTIONS AND
VERIFIED ANSWERS|GRADED A+
Question 1
1. A refrigeration plant has an evaporating pressure that corresponds to 25°F saturation temperature. The measured
vapor leaving the evaporator is 38°F. What is the evaporator outlet superheat?
A. 13°F
B. 63°F
C. 25°F
D. 38°F
CORRECT ANSWER
A. 13°F
Explanation: Superheat is actual vapor temperature minus saturation temperature: 38 − 25 = 13°F.
Question 2
2. When refrigerant pressure increases during compression, the saturation temperature generally:
A. Decreases
B. Increases
C. Becomes zero
D. Is unaffected by pressure
CORRECT ANSWER
B. Increases
Explanation: For a given refrigerant, saturation temperature generally rises as pressure rises.
Question 3
3. A compressor suction line carries refrigerant that should normally be:
A. High-pressure liquid
B. Low-pressure vapor
C. High-pressure vapor
D. Low-pressure liquid only
CORRECT ANSWER
B. Low-pressure vapor
Explanation: The suction line returns low-pressure refrigerant vapor from the evaporator toward the compressor.
,1 FDNY Z-51 / Q-01 PRACTICE EXAM
,Question 4
4. The main purpose of the condenser fan on an air-cooled condenser is to:
A. Increase refrigerant charge
B. Move air across the heat-transfer surface
C. Meter liquid refrigerant
D. Lubricate the compressor
CORRECT ANSWER
B. Move air across the heat-transfer surface
Explanation: The fan increases airflow across the condenser so heat can be rejected to the surrounding air.
Question 5
5. If the evaporator load increases while other conditions remain suitable, the refrigeration system willgenerally
need to:
A. Transfer more heat through the evaporator
B. Stop refrigerant circulation
C. Eliminate the compressor
D. Remove the condenser
CORRECT ANSWER
A. Transfer more heat through the evaporator
Explanation: A higher cooling load requires the evaporator to absorb more heat, with the system responding through
refrigerant flow and compressor capacity.
Question 6
6. A refrigeration cycle is best described as a process that:
A. Moves heat from a lower-temperature region to a higher-temperature heat sink using work
B. Creates heat from nothing
C. Destroys refrigerant
D. Moves heat only by natural convection
CORRECT ANSWER
A. Moves heat from a lower-temperature region to a higher-temperature heat sink using work
Explanation: Refrigeration uses work, normally compressor work, to transfer heat from a colder region to a warmer sink.
,2 FDNY Z-51 / Q-01 PRACTICE EXAM
,Question 7
7. Which condition is most directly associated with saturated liquid?
A. Liquid at its saturation condition before further sensible cooling
B. Vapor above saturation temperature
C. Superheated vapor
D. Compressed air
CORRECT ANSWER
A. Liquid at its saturation condition before further sensible cooling
Explanation: Saturated liquid is liquid at the saturation condition for its pressure; further cooling produces subcooling.
Question 8
8. Why is pressure-temperature information important to an operator?
A. It helps relate measured pressure to refrigerant saturation conditions
B. It eliminates the need for thermometers
C. It determines building occupancy
D. It replaces electrical testing
CORRECT ANSWER
A. It helps relate measured pressure to refrigerant saturation conditions
Explanation: Pressure-temperature relationships allow an operator to compare measured pressures with saturation
temperatures and evaluate superheat/subcooling.
Question 9
9. A reciprocating compressor's suction valve opens primarily when:
A. Cylinder conditions permit vapor to enter during the suction stroke
B. The condenser is full of liquid
C. The receiver is empty
D. The motor is disconnected
CORRECT ANSWER
A. Cylinder conditions permit vapor to enter during the suction stroke
Explanation: The suction valve admits low-pressure vapor into the cylinder during the appropriate part of the compressor
cycle.
, 3 FDNY Z-51 / Q-01 PRACTICE EXAM
