1|Page
Z-51 WRITTEN EXAM 2025| BRAND NEW ACTUAL
EXAM WITH 100% VERIFIED QUESTIONS AND
CORRECT SOLUTIONS| GUARANTEED VALUE PACK|
ACE YOUR GRADES.
The efficiency of the refrigerant cycle is affected by the operation of the
condenser. Of the following, a more efficient centrifugal compressor operation
results from:
A. Raising the condenser liquid level to the maximum
B. Lowering the chilled water set point
C. Raising the condenser head pressure
D. Lowering the condensing pressure - (answers)D. Lowering the condensing
pressure
The heat removed from the refrigerant in a condenser is:
A. Sensible and latent heat
B. Latent heat only
C. Radiant heat only
D. Sensible heat only - (answers)A. Sensible and latent heat
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
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suitable containers. According to the New York City fire code, you must ensure
that the containers:
A. Do not weigh more than 200 pounds when filled
B. Are approved by the US Department of Transportation
C. Are approved by the OSHA Association
D. Do not exceed 55 Gallons in capacity - (answers)B. Are approved by the US
Department of Transportation
Which of the following best describes how the cylinder unloader work?
A. Keep in the suction valve opened while the compressor is in the return stroke
B. Controls the clearance volume in the compressor with a solenoid
C. Controls the opening of the passage into the compressor with variable vanes
D. Unloads the piston to create less pressure - (answers)A. Keep in the suction
valve opened while the compressor is in the return stroke
In the most semi Hermetic compressors, the suction vapor is used to:
A. Removes oil from the motor housing
B. Cools the motor
C. Minimizes oil foaming
D. Removes oil foam from the shaft - (answers)B. Cools the motor
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The amount of refrigerant that flows through the orifices of a economizer is
determined by the:
A. Number of economizer stages
B. Temperature of the high side refrigerant
C. Number of compressor stages
D. Difference between high side and low side pressure - (answers)D. Difference
between high side and low side pressure
The installation of an inline refrigerant cleaning system is advisable:
A. For high pressure refrigerant systems
B. To purge non-condensables
C. For systems using toxic refrigerant
D. To remove impurities from the system - (answers)D. To remove impurities from
the system
The type of refrigerant system that is least likely to leak refrigerant into the
building space that are being cooled:
A. The direct vented closed system
B. The direct closed system
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C. Any system using reciprocating compressor
D. The indirect system - (answers)D. The indirect system
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 closet to:
A. 2.07
B. 4.41
C. 1.69
D. 1.84 - (answers)C. 1.69
A superheated vapor is a:
A. Dry vapor at the saturation temperature
B. Dry saturated vapor
C. Dry vapor above the saturation temperature
D. Vapor with minimal amount of included liquid - (answers)C. Dry vapor above
the saturation temperature
A refrigerant engineer verifies that a condenser water pump is cavitating. Of the
following the most likely cause for this condition is:
Z-51 WRITTEN EXAM 2025| BRAND NEW ACTUAL
EXAM WITH 100% VERIFIED QUESTIONS AND
CORRECT SOLUTIONS| GUARANTEED VALUE PACK|
ACE YOUR GRADES.
The efficiency of the refrigerant cycle is affected by the operation of the
condenser. Of the following, a more efficient centrifugal compressor operation
results from:
A. Raising the condenser liquid level to the maximum
B. Lowering the chilled water set point
C. Raising the condenser head pressure
D. Lowering the condensing pressure - (answers)D. Lowering the condensing
pressure
The heat removed from the refrigerant in a condenser is:
A. Sensible and latent heat
B. Latent heat only
C. Radiant heat only
D. Sensible heat only - (answers)A. Sensible and latent heat
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
,2|Page
suitable containers. According to the New York City fire code, you must ensure
that the containers:
A. Do not weigh more than 200 pounds when filled
B. Are approved by the US Department of Transportation
C. Are approved by the OSHA Association
D. Do not exceed 55 Gallons in capacity - (answers)B. Are approved by the US
Department of Transportation
Which of the following best describes how the cylinder unloader work?
A. Keep in the suction valve opened while the compressor is in the return stroke
B. Controls the clearance volume in the compressor with a solenoid
C. Controls the opening of the passage into the compressor with variable vanes
D. Unloads the piston to create less pressure - (answers)A. Keep in the suction
valve opened while the compressor is in the return stroke
In the most semi Hermetic compressors, the suction vapor is used to:
A. Removes oil from the motor housing
B. Cools the motor
C. Minimizes oil foaming
D. Removes oil foam from the shaft - (answers)B. Cools the motor
,3|Page
The amount of refrigerant that flows through the orifices of a economizer is
determined by the:
A. Number of economizer stages
B. Temperature of the high side refrigerant
C. Number of compressor stages
D. Difference between high side and low side pressure - (answers)D. Difference
between high side and low side pressure
The installation of an inline refrigerant cleaning system is advisable:
A. For high pressure refrigerant systems
B. To purge non-condensables
C. For systems using toxic refrigerant
D. To remove impurities from the system - (answers)D. To remove impurities from
the system
The type of refrigerant system that is least likely to leak refrigerant into the
building space that are being cooled:
A. The direct vented closed system
B. The direct closed system
, 4|Page
C. Any system using reciprocating compressor
D. The indirect system - (answers)D. The indirect system
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 closet to:
A. 2.07
B. 4.41
C. 1.69
D. 1.84 - (answers)C. 1.69
A superheated vapor is a:
A. Dry vapor at the saturation temperature
B. Dry saturated vapor
C. Dry vapor above the saturation temperature
D. Vapor with minimal amount of included liquid - (answers)C. Dry vapor above
the saturation temperature
A refrigerant engineer verifies that a condenser water pump is cavitating. Of the
following the most likely cause for this condition is:
