FDNY Z51/ WRITTEN Z51 TEST EXAM RECENT
2024- 2026VERSION UPDATED WITH ALL 220
QUESTIONS AND DETAILED ANSWERS
GRADED A
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: - CORRECT ANSWER✔️
Lowering the condenser pressure
The heat removed from the refrigerant in a condenser is: -
CORRECT 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
sultable containers. According to the New York City fire code, you
must ensure that the containers: - CORRECT ANSWER✔️
approved by us department of transportation
Which of the following best describes how the cylinder unloader
work? - CORRECT ANSWER✔️ Keep in the suction valve
opened while the compressor is in return stroke.
In most semi Hermetic compressors, the suction vapor is used to:
- CORRECT ANSWER✔️ Cools the motor
,The amount of refrigerant that flows through the orifices of a
economizer is determined by the: - CORRECT ANSWER✔️
Difference between high and low side pressure
The Installation of an Inline refrigerant cleaning system is
advisable: - CORRECT ANSWER✔️ To remove impurities from
the system
The type of refrigerant system that is least likaly to leak refrigerant
into the building space that are being cooled: - CORRECT
ANSWER✔️ The Indirect system
The suction pressure of a reciprocating compressor is 65 PSIG.
The discharge pressure of this compressor is 120 PIG. The
atmospheric is 14.7 PSI. The compression ratio for the given
condition is
closest to: - CORRECT ANSWER✔️ 1.69
Discharge/suction
A superheated vapor is a: - 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
The chilled water supply to the bullding Is 55F. 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
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 a 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 reading 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✔️ Malfunction of unloader
, 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 property, af the end of the
evaporator will contain: - CORRECT ANSWER✔️ Only
superheated vapor
What Information is not contained in a Material Safety Data
Sheet-MSD5? - CORRECT ANSWER✔️ Cost of material
In a steam turbing, what is the function of the Kingsbury thrust
bearing - CORRECT ANSWER✔️ Maintain first stage steam
pressure
A centrifugal water pump is considered to be 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✔️ Lever type tubing bender
A reciprocating compressor is making a knocking sound during
operation. If the refrigerant worn parts are not causing the
2024- 2026VERSION UPDATED WITH ALL 220
QUESTIONS AND DETAILED ANSWERS
GRADED A
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: - CORRECT ANSWER✔️
Lowering the condenser pressure
The heat removed from the refrigerant in a condenser is: -
CORRECT 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
sultable containers. According to the New York City fire code, you
must ensure that the containers: - CORRECT ANSWER✔️
approved by us department of transportation
Which of the following best describes how the cylinder unloader
work? - CORRECT ANSWER✔️ Keep in the suction valve
opened while the compressor is in return stroke.
In most semi Hermetic compressors, the suction vapor is used to:
- CORRECT ANSWER✔️ Cools the motor
,The amount of refrigerant that flows through the orifices of a
economizer is determined by the: - CORRECT ANSWER✔️
Difference between high and low side pressure
The Installation of an Inline refrigerant cleaning system is
advisable: - CORRECT ANSWER✔️ To remove impurities from
the system
The type of refrigerant system that is least likaly to leak refrigerant
into the building space that are being cooled: - CORRECT
ANSWER✔️ The Indirect system
The suction pressure of a reciprocating compressor is 65 PSIG.
The discharge pressure of this compressor is 120 PIG. The
atmospheric is 14.7 PSI. The compression ratio for the given
condition is
closest to: - CORRECT ANSWER✔️ 1.69
Discharge/suction
A superheated vapor is a: - 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
The chilled water supply to the bullding Is 55F. 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
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 a 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 reading 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✔️ Malfunction of unloader
, 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 property, af the end of the
evaporator will contain: - CORRECT ANSWER✔️ Only
superheated vapor
What Information is not contained in a Material Safety Data
Sheet-MSD5? - CORRECT ANSWER✔️ Cost of material
In a steam turbing, what is the function of the Kingsbury thrust
bearing - CORRECT ANSWER✔️ Maintain first stage steam
pressure
A centrifugal water pump is considered to be 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✔️ Lever type tubing bender
A reciprocating compressor is making a knocking sound during
operation. If the refrigerant worn parts are not causing the
