Z-51 REFRIGERATION TEST 2025-2026 ACTUAL EXAM
QUESTIONS AND CORRECT DETAILED ANSWERS
|ALREADY GRADED A+
The type of refrigerant system that is least likely to leak refrigerant
into the building space that are being cooled: - CORRECT 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: -
CORRECT ANSWER 1.69
A superheated vapor is: - CORRECT 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: -
CORRECT ANSWER A faulty cooling tower water level controller
A centrifugal water pump is known as a lift pump when the: - CORRECT
ANSWER The water supply to the pump suction inlet is below the
pump level
A TXV is used to maintain constant: - CORRECT ANSWER Evaporator
superheat
1
,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? - CORRECT ANSWER Yes, this temp is too high for human
comfort purposes
The packing gland of a centrifugal pump serves to: - CORRECT 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: - CORRECT ANSWER Operation of the hot gas
bypass valve
The most important reason to sub-cool the refrigerant in the condenser
is to ensure that: - CORRECT 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? - CORRECT ANSWER An expansion
valve that is open too wide
2
,A low side float valve is used to maintain: - CORRECT ANSWER The
level of the refrigerant in the evaporator
Regarding fire safety, which ASHRAE refrigerant safety classification
indicates no flammability and lower toxicity? - CORRECT ANSWER A1
When an expansion valve is operating properly, at the end of the
evaporator will contain: - CORRECT ANSWER Only superheated vapor
What information is not contained in a Material Safety Data Sheet? -
CORRECT ANSWER Cost of the material
In a steam turbine, what is the function of the Kingsbury thrust
bearing? - CORRECT ANSWER Maintain axial positioning of the rotor
shaft
A centrifugal water pump is considered to the fully primed when? -
CORRECT 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? - CORRECT 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,
3
, what probably the cause? - CORRECT 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: - CORRECT ANSWER Where no
liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the
system: - CORRECT ANSWER Should not be opened until all vapor has
been recovered
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? - CORRECT
ANSWER The compressor efficiency is decreasing
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? - CORRECT
ANSWER Add additional make up water to the cooling tower
A rooftop water cooling tower is connected to a water pump in the
building basement with a 12 inch diameter pipe. With the pipe turned
4
QUESTIONS AND CORRECT DETAILED ANSWERS
|ALREADY GRADED A+
The type of refrigerant system that is least likely to leak refrigerant
into the building space that are being cooled: - CORRECT 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: -
CORRECT ANSWER 1.69
A superheated vapor is: - CORRECT 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: -
CORRECT ANSWER A faulty cooling tower water level controller
A centrifugal water pump is known as a lift pump when the: - CORRECT
ANSWER The water supply to the pump suction inlet is below the
pump level
A TXV is used to maintain constant: - CORRECT ANSWER Evaporator
superheat
1
,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? - CORRECT ANSWER Yes, this temp is too high for human
comfort purposes
The packing gland of a centrifugal pump serves to: - CORRECT 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: - CORRECT ANSWER Operation of the hot gas
bypass valve
The most important reason to sub-cool the refrigerant in the condenser
is to ensure that: - CORRECT 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? - CORRECT ANSWER An expansion
valve that is open too wide
2
,A low side float valve is used to maintain: - CORRECT ANSWER The
level of the refrigerant in the evaporator
Regarding fire safety, which ASHRAE refrigerant safety classification
indicates no flammability and lower toxicity? - CORRECT ANSWER A1
When an expansion valve is operating properly, at the end of the
evaporator will contain: - CORRECT ANSWER Only superheated vapor
What information is not contained in a Material Safety Data Sheet? -
CORRECT ANSWER Cost of the material
In a steam turbine, what is the function of the Kingsbury thrust
bearing? - CORRECT ANSWER Maintain axial positioning of the rotor
shaft
A centrifugal water pump is considered to the fully primed when? -
CORRECT 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? - CORRECT 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,
3
, what probably the cause? - CORRECT 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: - CORRECT ANSWER Where no
liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the
system: - CORRECT ANSWER Should not be opened until all vapor has
been recovered
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? - CORRECT
ANSWER The compressor efficiency is decreasing
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? - CORRECT
ANSWER Add additional make up water to the cooling tower
A rooftop water cooling tower is connected to a water pump in the
building basement with a 12 inch diameter pipe. With the pipe turned
4
