1
FDNY Z51 RMO FINAL EXAM - COMPREHENSIVE EXAM
2026||NEWEST EXAM PREPARATION WITH COMPLETE
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES |
ALREADY GRADED A+| |BRAND NEW VERSION!!
SECTION 1: REFRIGERATION FUNDAMENTALS (Questions 1-40)
1. In most semi-hermetic compressors, the suction vapor is used to:
A) Cool the condenser
B) Cool the motor
C) Heat the crankcase
D) Increase discharge pressure
Answer: B) Cool the motor
Rationale: In semi-hermetic compressors, suction vapor is drawn over the
motor windings to provide cooling before being compressed. This is a key
design feature that allows the motor to operate within the sealed housing.
2. The amount of refrigerant that flows through the orifices of an economizer
is determined by:
A) The temperature of the refrigerant
B) The difference between the high side and low side pressure
C) The size of the compressor
D) The ambient temperature
, 2
Answer: B) The difference between the high side and low side pressure
Rationale: The pressure differential between the high side and low side
determines the flow rate through the economizer orifices. This pressure
difference drives the refrigerant through the metering orifices.
3. When an expansion valve is operating properly, at the end of the
evaporator will contain:
A) A mixture of liquid and vapor
B) Only superheated vapor
C) Subcooled liquid
D) Saturated vapor
Answer: B) Only superheated vapor
Rationale: A properly operating expansion valve maintains the correct
superheat at the evaporator outlet. Superheated vapor ensures no liquid
refrigerant carries over to the compressor, preventing slugging.
4. The efficiency of the refrigerant cycle is affected by the operation of the
condenser. A more efficient centrifugal compressor operation results from:
A) Increasing the condenser pressure
B) Lowering the condenser pressure
C) Increasing the evaporator pressure
D) Decreasing the evaporator pressure
, 3
Answer: B) Lowering the condenser pressure
Rationale: Lower condenser pressure reduces the compression ratio, which
decreases the work required by the compressor. This improves overall cycle
efficiency and reduces power consumption.
5. Refrigerants are characterized by their physical properties including
flashpoint, refrigeration effect and others. Of the refrigerants in commercial
and industrial use, the highest latent heat and refrigerant effect is:
A) R-134a
B) R-22
C) Ammonia
D) R-410A
Answer: C) Ammonia
Rationale: Ammonia (R-717) has the highest latent heat of vaporization
among common refrigerants, making it extremely efficient. Its refrigeration
effect per pound is significantly higher than other refrigerants.
6. Which of the following ASHRAE refrigerant safety classifications is the most
toxic?
A) A1
B) A2
C) B2
D) B3
, 4
Answer: D) B3
Rationale: The ASHRAE classification system uses letters for toxicity (A = lower
toxicity, B = higher toxicity) and numbers for flammability (1 = no flame
propagation, 3 = higher flammability). B3 represents the highest toxicity and
highest flammability.*
7. Which of the following ASHRAE refrigerant safety classifications is the most
flammable?
A) A1
B) A2
C) A3
D) B1
Answer: C) A3
Rationale: The number 3 in ASHRAE classification indicates higher
flammability. A3 refrigerants have lower toxicity but higher flammability, such
as propane (R-290).
8. In an indirect refrigeration system, of the following, the one that would
NOT be used as a cooling medium for building spaces being cooled is:**
A) Glycol
B) Brine solution
C) R-22
D) Chilled water
FDNY Z51 RMO FINAL EXAM - COMPREHENSIVE EXAM
2026||NEWEST EXAM PREPARATION WITH COMPLETE
QUESTIONS AND CORRECT ANSWERS WITH RATIONALES |
ALREADY GRADED A+| |BRAND NEW VERSION!!
SECTION 1: REFRIGERATION FUNDAMENTALS (Questions 1-40)
1. In most semi-hermetic compressors, the suction vapor is used to:
A) Cool the condenser
B) Cool the motor
C) Heat the crankcase
D) Increase discharge pressure
Answer: B) Cool the motor
Rationale: In semi-hermetic compressors, suction vapor is drawn over the
motor windings to provide cooling before being compressed. This is a key
design feature that allows the motor to operate within the sealed housing.
2. The amount of refrigerant that flows through the orifices of an economizer
is determined by:
A) The temperature of the refrigerant
B) The difference between the high side and low side pressure
C) The size of the compressor
D) The ambient temperature
, 2
Answer: B) The difference between the high side and low side pressure
Rationale: The pressure differential between the high side and low side
determines the flow rate through the economizer orifices. This pressure
difference drives the refrigerant through the metering orifices.
3. When an expansion valve is operating properly, at the end of the
evaporator will contain:
A) A mixture of liquid and vapor
B) Only superheated vapor
C) Subcooled liquid
D) Saturated vapor
Answer: B) Only superheated vapor
Rationale: A properly operating expansion valve maintains the correct
superheat at the evaporator outlet. Superheated vapor ensures no liquid
refrigerant carries over to the compressor, preventing slugging.
4. The efficiency of the refrigerant cycle is affected by the operation of the
condenser. A more efficient centrifugal compressor operation results from:
A) Increasing the condenser pressure
B) Lowering the condenser pressure
C) Increasing the evaporator pressure
D) Decreasing the evaporator pressure
, 3
Answer: B) Lowering the condenser pressure
Rationale: Lower condenser pressure reduces the compression ratio, which
decreases the work required by the compressor. This improves overall cycle
efficiency and reduces power consumption.
5. Refrigerants are characterized by their physical properties including
flashpoint, refrigeration effect and others. Of the refrigerants in commercial
and industrial use, the highest latent heat and refrigerant effect is:
A) R-134a
B) R-22
C) Ammonia
D) R-410A
Answer: C) Ammonia
Rationale: Ammonia (R-717) has the highest latent heat of vaporization
among common refrigerants, making it extremely efficient. Its refrigeration
effect per pound is significantly higher than other refrigerants.
6. Which of the following ASHRAE refrigerant safety classifications is the most
toxic?
A) A1
B) A2
C) B2
D) B3
, 4
Answer: D) B3
Rationale: The ASHRAE classification system uses letters for toxicity (A = lower
toxicity, B = higher toxicity) and numbers for flammability (1 = no flame
propagation, 3 = higher flammability). B3 represents the highest toxicity and
highest flammability.*
7. Which of the following ASHRAE refrigerant safety classifications is the most
flammable?
A) A1
B) A2
C) A3
D) B1
Answer: C) A3
Rationale: The number 3 in ASHRAE classification indicates higher
flammability. A3 refrigerants have lower toxicity but higher flammability, such
as propane (R-290).
8. In an indirect refrigeration system, of the following, the one that would
NOT be used as a cooling medium for building spaces being cooled is:**
A) Glycol
B) Brine solution
C) R-22
D) Chilled water
