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# FDNY Z-51 REFRIGERATION ENGINEER
EXAM: COMPLETE PRACTICE QUESTION
BANK
## VERIFIED STUDY GUIDE FOR THE Q-01
CERTIFICATE OF QUALIFICATION
## Section 1: Refrigeration Cycles & System Fundamentals
**Question 1**
The efficiency of the refrigerant cycle is affected by the operations of the
condenser. A more efficient centrifugal compressor operation results from:
A) Increasing the condensing pressure
B) Lowering the condensing pressure
C) Increasing the evaporator pressure
D) Decreasing the suction pressure
E) Raising the compression ratio
**Correct Answer: B) Lowering the condensing pressure**
**Rationale:** Lowering the condensing pressure reduces the pressure differential
between the high and low sides of the system. This decreases the work required for
compression, improving the Coefficient of Performance (COP) and overall system
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efficiency. High condensing pressure is typically caused by fouled condenser tubes,
non-condensables, or insufficient cooling water flow .
---
**Question 2**
The heat removed from the refrigerant in a condenser is:
A) Sensible heat only
B) Latent heat only
C) Both sensible and latent heat
D) Superheat only
E) Subcooling only
**Correct Answer: C) Both sensible and latent heat**
**Rationale:** The condenser removes both sensible and latent heat from the
refrigerant. The desuperheating section removes sensible heat to bring the
refrigerant to its saturation temperature. The condensing section removes latent
heat as the refrigerant changes from vapor to liquid at constant temperature .
---
**Question 3**
In an indirect refrigeration system, which of the following would NOT be used as a
cooling medium for the building spaces being cooled?
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A) Chilled water
B) Brine
C) R-22 refrigerant
D) Glycol solution
E) Secondary coolant
**Correct Answer: C) R-22 refrigerant**
**Rationale:** An indirect refrigeration system uses a secondary coolant (such as
chilled water, brine, or glycol) to transfer cooling to the spaces being cooled, while
the refrigerant remains in the machinery room. R-22 is a primary refrigerant that
would be used in a direct expansion system, not as a cooling medium in an indirect
system .
---
**Question 4**
Under normal operating conditions, the refrigerant enters the compressor as:
A) High pressure, subcooled liquid
B) Low pressure, superheated vapor
C) High pressure, superheated vapor
D) Low pressure, saturated liquid
E) High pressure, saturated vapor
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**Correct Answer: B) Low pressure, superheated vapor**
**Rationale:** The refrigerant entering the compressor should be a low-pressure,
superheated vapor to ensure no liquid droplets enter the compressor. Liquid
slugging can cause severe damage to the compressor valves and pistons. A properly
adjusted expansion valve maintains at least 10-15°F of superheat at the compressor
suction .
---
**Question 5**
In a refrigeration system, the amount of refrigerant that flows through the orifices
of an economizer is determined by the:
A) Suction pressure only
B) Discharge pressure only
C) Differences between high side and low side pressure
D) Refrigerant temperature
E) Compressor speed
**Correct Answer: C) Differences between high side and low side pressure**
**Rationale:** The economizer uses a pressure differential to allow flash gas to
bypass the main expansion device, improving system efficiency. The flow rate
through the economizer orifices is directly proportional to the pressure difference
between the high and low sides of the system .
# FDNY Z-51 REFRIGERATION ENGINEER
EXAM: COMPLETE PRACTICE QUESTION
BANK
## VERIFIED STUDY GUIDE FOR THE Q-01
CERTIFICATE OF QUALIFICATION
## Section 1: Refrigeration Cycles & System Fundamentals
**Question 1**
The efficiency of the refrigerant cycle is affected by the operations of the
condenser. A more efficient centrifugal compressor operation results from:
A) Increasing the condensing pressure
B) Lowering the condensing pressure
C) Increasing the evaporator pressure
D) Decreasing the suction pressure
E) Raising the compression ratio
**Correct Answer: B) Lowering the condensing pressure**
**Rationale:** Lowering the condensing pressure reduces the pressure differential
between the high and low sides of the system. This decreases the work required for
compression, improving the Coefficient of Performance (COP) and overall system
,2|Page
efficiency. High condensing pressure is typically caused by fouled condenser tubes,
non-condensables, or insufficient cooling water flow .
---
**Question 2**
The heat removed from the refrigerant in a condenser is:
A) Sensible heat only
B) Latent heat only
C) Both sensible and latent heat
D) Superheat only
E) Subcooling only
**Correct Answer: C) Both sensible and latent heat**
**Rationale:** The condenser removes both sensible and latent heat from the
refrigerant. The desuperheating section removes sensible heat to bring the
refrigerant to its saturation temperature. The condensing section removes latent
heat as the refrigerant changes from vapor to liquid at constant temperature .
---
**Question 3**
In an indirect refrigeration system, which of the following would NOT be used as a
cooling medium for the building spaces being cooled?
,3|Page
A) Chilled water
B) Brine
C) R-22 refrigerant
D) Glycol solution
E) Secondary coolant
**Correct Answer: C) R-22 refrigerant**
**Rationale:** An indirect refrigeration system uses a secondary coolant (such as
chilled water, brine, or glycol) to transfer cooling to the spaces being cooled, while
the refrigerant remains in the machinery room. R-22 is a primary refrigerant that
would be used in a direct expansion system, not as a cooling medium in an indirect
system .
---
**Question 4**
Under normal operating conditions, the refrigerant enters the compressor as:
A) High pressure, subcooled liquid
B) Low pressure, superheated vapor
C) High pressure, superheated vapor
D) Low pressure, saturated liquid
E) High pressure, saturated vapor
, 4|Page
**Correct Answer: B) Low pressure, superheated vapor**
**Rationale:** The refrigerant entering the compressor should be a low-pressure,
superheated vapor to ensure no liquid droplets enter the compressor. Liquid
slugging can cause severe damage to the compressor valves and pistons. A properly
adjusted expansion valve maintains at least 10-15°F of superheat at the compressor
suction .
---
**Question 5**
In a refrigeration system, the amount of refrigerant that flows through the orifices
of an economizer is determined by the:
A) Suction pressure only
B) Discharge pressure only
C) Differences between high side and low side pressure
D) Refrigerant temperature
E) Compressor speed
**Correct Answer: C) Differences between high side and low side pressure**
**Rationale:** The economizer uses a pressure differential to allow flash gas to
bypass the main expansion device, improving system efficiency. The flow rate
through the economizer orifices is directly proportional to the pressure difference
between the high and low sides of the system .
