CURRENTLY TESTING Z-51 REFRIGERATION EXAM
QUESTIONS WITH ACTUAL CORRECT DETAILED
ANSWERS
Efficiency of the refrigerant cycle is affected by the operations of the condenser. Of the following, a more
efficient centrifugal compressor operation results from: - ANSWER-Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - ANSWER-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 suitable containers. According to the NYC Fire
Code, you must ensure that the containers: - ANSWER-Are approved by the US Dept. of Transportation
Which of the following best describes how the cylinder unloader works? - ANSWER-Keep in the suction
valve opened while the compressor is in the return stroke
In most semi-hermetic compressors, the suction vapor is used to: - ANSWER-Cool the motor
The amount of refrigerant that flows through the orifices of an economizer is determined by the: -
ANSWER-Differences between the high side and low side pressure
,The installation of an inline refrigerant cleaning system is advisable: - ANSWER-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: - ANSWER-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 closest to: -
ANSWER-1.69
A superheated vapor is: - ANSWER-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: - ANSWER-A faulty cooling tower water level controller
A centrifugal water pump is known as a lift pump when the: - ANSWER-The water supply to the pump
suction inlet is below the pump level
A TXV is used to maintain constant: - ANSWER-Evaporator superheat
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? - ANSWER-Yes, this temp is too high for human comfort purposes
The packing gland of a centrifugal pump serves to: - ANSWER-The drip part of the packing gland gives
evidence that there is water in the pump
Capacity control of reciprocating hermetic compressor is typically achieved through: - ANSWER-
Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to ensure that: - ANSWER-A
pure liquid refrigerant will enter the metering device
, 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? - ANSWER-An expansion valve that is open too wide
A low side float valve is used to maintain: - ANSWER-The level of the refrigerant in the evaporator
Regarding fire safety, which ASHRAE refrigerant safety classification indicates no flammability and lower
toxicity? - ANSWER-A1
When an expansion valve is operating properly, at the end of the evaporator will contain: - ANSWER-Only
superheated vapor
What information is not contained in a Material Safety Data Sheet? - ANSWER-Cost of the material
In a steam turbine, what is the function of the Kingsbury thrust bearing? - ANSWER-Maintain axial
positioning of the rotor shaft
A centrifugal water pump is considered to the fully primed when? - ANSWER-The pump is full of liquid
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? - ANSWER-Level
type tubing bender
A reciprocating compressor is making a knocking sound during operation. If the refrigerant worn parts
are not causing the knocking, what probably the cause? - ANSWER-Slugging of the liquid refrigerant
In order for a refrigerant to become superheated, it must be heated in a section of the low side
refrigerant line: - ANSWER-Where no liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the system: - ANSWER-Should not be
opened until all vapor has been recovered
QUESTIONS WITH ACTUAL CORRECT DETAILED
ANSWERS
Efficiency of the refrigerant cycle is affected by the operations of the condenser. Of the following, a more
efficient centrifugal compressor operation results from: - ANSWER-Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - ANSWER-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 suitable containers. According to the NYC Fire
Code, you must ensure that the containers: - ANSWER-Are approved by the US Dept. of Transportation
Which of the following best describes how the cylinder unloader works? - ANSWER-Keep in the suction
valve opened while the compressor is in the return stroke
In most semi-hermetic compressors, the suction vapor is used to: - ANSWER-Cool the motor
The amount of refrigerant that flows through the orifices of an economizer is determined by the: -
ANSWER-Differences between the high side and low side pressure
,The installation of an inline refrigerant cleaning system is advisable: - ANSWER-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: - ANSWER-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 closest to: -
ANSWER-1.69
A superheated vapor is: - ANSWER-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: - ANSWER-A faulty cooling tower water level controller
A centrifugal water pump is known as a lift pump when the: - ANSWER-The water supply to the pump
suction inlet is below the pump level
A TXV is used to maintain constant: - ANSWER-Evaporator superheat
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? - ANSWER-Yes, this temp is too high for human comfort purposes
The packing gland of a centrifugal pump serves to: - ANSWER-The drip part of the packing gland gives
evidence that there is water in the pump
Capacity control of reciprocating hermetic compressor is typically achieved through: - ANSWER-
Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to ensure that: - ANSWER-A
pure liquid refrigerant will enter the metering device
, 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? - ANSWER-An expansion valve that is open too wide
A low side float valve is used to maintain: - ANSWER-The level of the refrigerant in the evaporator
Regarding fire safety, which ASHRAE refrigerant safety classification indicates no flammability and lower
toxicity? - ANSWER-A1
When an expansion valve is operating properly, at the end of the evaporator will contain: - ANSWER-Only
superheated vapor
What information is not contained in a Material Safety Data Sheet? - ANSWER-Cost of the material
In a steam turbine, what is the function of the Kingsbury thrust bearing? - ANSWER-Maintain axial
positioning of the rotor shaft
A centrifugal water pump is considered to the fully primed when? - ANSWER-The pump is full of liquid
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? - ANSWER-Level
type tubing bender
A reciprocating compressor is making a knocking sound during operation. If the refrigerant worn parts
are not causing the knocking, what probably the cause? - ANSWER-Slugging of the liquid refrigerant
In order for a refrigerant to become superheated, it must be heated in a section of the low side
refrigerant line: - ANSWER-Where no liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the system: - ANSWER-Should not be
opened until all vapor has been recovered
