FDNY Z-51 REFRIGERATION EXAM WITH
ACTUAL CORRECT QUESTIONS AND
VERIFIED DETAILED ANSWERS|
CURRENTLY TESTING VERSION | ALREADY
GRADED A+|NEWEST |2026-2027
1.Efficiency of the refrigerant cycle is affected by the operations of the condenser. Of
the following, a more efficient centrifugal compressor operation results from:
Lowering the condensing pressure
2.The heat removed from the refrigerant in a condenser is:
Sensible and latent heat
3.The refrigerant unit that you have been assigned to is being taken out of service for
a major repair. You have been assigned to withdraw refrigerant for storage in suitable
containers. According to the NYC Fire Code, you must ensure that the containers:
Are approved by the US Dept. of Transportation
4.Which of the following best describes how the cylinder unloader works?
Keep in the suction valve opened while the compressor is in the return stroke
5.In most semi-hermetic compressors, the suction vapor is used to:
Cool the motor
6.The amount of refrigerant that flows through the orifices of an economizer is
determined by the:
Differences between the high side and low side pressure
7.The installation of an inline refrigerant cleaning system is advisable:
To remove impurities from the system
8.The type of refrigerant system that is least likely to leak refrigerant into the building
space that are being cooled:
Indirect system
9.The suction pressure of a reciprocating compressor is 65 PSIG. The discharge
pressure of this compressor is 120 PSIG. The atmospheric is 14.7 PSI. The
compression ratio for the given condition is closest to:
1|Page
, 1.69
10.A superheated vapor is:
Dry vapor above the saturation temperature
11.A refrigerant engineer verifies that a condenser water pump is cavitating. Of the
following, the most likely cause for this condition is:
A faulty cooling tower water level controller
12.A centrifugal water pump is known as a lift pump when the:
The water supply to the pump suction inlet is below the pump level
13.A TXV is used to maintain constant:
Evaporator superheat
14.The chilled water supply to the building is 55 deg F. If the chiller is being used for
human comfort, should you be concerned about this, and why?
Yes, this temp is too high for human comfort purposes
15.The packing gland of a centrifugal pump serves to:
The drip part of the packing gland gives evidence that there is water in the pump
16.Capacity control of reciprocating hermetic compressor is typically achieved
through:
Operation of the hot gas bypass valve
17.The most important reason to sub-cool the refrigerant in the condenser is to
ensure that:
A pure liquid refrigerant will enter the metering device
18.A refrigeration engineer is logging readings from a reciprocating system.
Compressor discharge temperature have dropped significantly and the suction line
pressure is high. Which of the following that may be causing this set of condition?
An expansion valve that is open too wide
19.A low side float valve is used to maintain:
The level of the refrigerant in the evaporator
20.Regarding fire safety, which ASHRAE refrigerant safety classification indicates no
flammability and lower toxicity?
A1
2|Page
, 21.When an expansion valve is operating properly, at the end of the evaporator will
contain:
Only superheated vapor
22.What information is not contained in a Material Safety Data Sheet?
Cost of the material
23.In a steam turbine, what is the function of the Kingsbury thrust bearing?
Maintain axial positioning of the rotor shaft
24.A centrifugal water pump is considered to the fully primed when?
The pump is full of liquid
25.Copper tubing refrigerant lines must be installed for a new system. It is a well
known service practice that tubing collapses at bends that must be made, the
refrigerant engineer should use?
Level type tubing bender
26.A reciprocating compressor is making a knocking sound during operation. If the
refrigerant worn parts are not causing the knocking, what probably the cause?
Slugging of the liquid refrigerant
27.In order for a refrigerant to become superheated, it must be heated in a section of
the low side refrigerant line:
Where no liquid refrigerant is present
28.All liquid has been recovered from a system to be overhauled, the system:
Should not be opened until all vapor has been recovered
29.When a refrigerant engineer uses a portable compressor recovery unit to remove
vapor refrigerant from a refrigeration system the removal rate of the refrigerant will
gradually slow down because?
The compressor efficiency is decreasing
30.You are the engineer running a 2000-ton (steam driven turbine) centrifugal
refrigeration system, a refrigeration system supplies chilled water to a college
campus with multiple buildings. During the course of making your rounds, you check
the 9 cell cooling tower on the roof. You note the water level in all of the cooling
tower cells is very low. Which one of the following immediate actions would take?
Add additional make up water to the cooling tower
3|Page
ACTUAL CORRECT QUESTIONS AND
VERIFIED DETAILED ANSWERS|
CURRENTLY TESTING VERSION | ALREADY
GRADED A+|NEWEST |2026-2027
1.Efficiency of the refrigerant cycle is affected by the operations of the condenser. Of
the following, a more efficient centrifugal compressor operation results from:
Lowering the condensing pressure
2.The heat removed from the refrigerant in a condenser is:
Sensible and latent heat
3.The refrigerant unit that you have been assigned to is being taken out of service for
a major repair. You have been assigned to withdraw refrigerant for storage in suitable
containers. According to the NYC Fire Code, you must ensure that the containers:
Are approved by the US Dept. of Transportation
4.Which of the following best describes how the cylinder unloader works?
Keep in the suction valve opened while the compressor is in the return stroke
5.In most semi-hermetic compressors, the suction vapor is used to:
Cool the motor
6.The amount of refrigerant that flows through the orifices of an economizer is
determined by the:
Differences between the high side and low side pressure
7.The installation of an inline refrigerant cleaning system is advisable:
To remove impurities from the system
8.The type of refrigerant system that is least likely to leak refrigerant into the building
space that are being cooled:
Indirect system
9.The suction pressure of a reciprocating compressor is 65 PSIG. The discharge
pressure of this compressor is 120 PSIG. The atmospheric is 14.7 PSI. The
compression ratio for the given condition is closest to:
1|Page
, 1.69
10.A superheated vapor is:
Dry vapor above the saturation temperature
11.A refrigerant engineer verifies that a condenser water pump is cavitating. Of the
following, the most likely cause for this condition is:
A faulty cooling tower water level controller
12.A centrifugal water pump is known as a lift pump when the:
The water supply to the pump suction inlet is below the pump level
13.A TXV is used to maintain constant:
Evaporator superheat
14.The chilled water supply to the building is 55 deg F. If the chiller is being used for
human comfort, should you be concerned about this, and why?
Yes, this temp is too high for human comfort purposes
15.The packing gland of a centrifugal pump serves to:
The drip part of the packing gland gives evidence that there is water in the pump
16.Capacity control of reciprocating hermetic compressor is typically achieved
through:
Operation of the hot gas bypass valve
17.The most important reason to sub-cool the refrigerant in the condenser is to
ensure that:
A pure liquid refrigerant will enter the metering device
18.A refrigeration engineer is logging readings from a reciprocating system.
Compressor discharge temperature have dropped significantly and the suction line
pressure is high. Which of the following that may be causing this set of condition?
An expansion valve that is open too wide
19.A low side float valve is used to maintain:
The level of the refrigerant in the evaporator
20.Regarding fire safety, which ASHRAE refrigerant safety classification indicates no
flammability and lower toxicity?
A1
2|Page
, 21.When an expansion valve is operating properly, at the end of the evaporator will
contain:
Only superheated vapor
22.What information is not contained in a Material Safety Data Sheet?
Cost of the material
23.In a steam turbine, what is the function of the Kingsbury thrust bearing?
Maintain axial positioning of the rotor shaft
24.A centrifugal water pump is considered to the fully primed when?
The pump is full of liquid
25.Copper tubing refrigerant lines must be installed for a new system. It is a well
known service practice that tubing collapses at bends that must be made, the
refrigerant engineer should use?
Level type tubing bender
26.A reciprocating compressor is making a knocking sound during operation. If the
refrigerant worn parts are not causing the knocking, what probably the cause?
Slugging of the liquid refrigerant
27.In order for a refrigerant to become superheated, it must be heated in a section of
the low side refrigerant line:
Where no liquid refrigerant is present
28.All liquid has been recovered from a system to be overhauled, the system:
Should not be opened until all vapor has been recovered
29.When a refrigerant engineer uses a portable compressor recovery unit to remove
vapor refrigerant from a refrigeration system the removal rate of the refrigerant will
gradually slow down because?
The compressor efficiency is decreasing
30.You are the engineer running a 2000-ton (steam driven turbine) centrifugal
refrigeration system, a refrigeration system supplies chilled water to a college
campus with multiple buildings. During the course of making your rounds, you check
the 9 cell cooling tower on the roof. You note the water level in all of the cooling
tower cells is very low. Which one of the following immediate actions would take?
Add additional make up water to the cooling tower
3|Page
