FDNY Z51 RMO FINAL 2025QUESTIONS WITH
SOLUTIONS 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
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 condenser pressure - Correct Answer - 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 - Correct Answer - sensible and latent heat
The refrigerant unit that you have been assigned to is being taken out of service for major repair. You
have been assigned to withdraw refrigerant from storage in suitable containers. According to the NYC
fire code, you must ensure that the containers
a. do not weigh more than 200lbs when filled
b. Are approved by the US Department of Transportation (DOT)
c. are approved by the OSHA association
d. do not exceed 55 gallon in capacity - Correct Answer - Are approved by the US Department of
Transportation (DOT)
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 pistons to create less pressure - Correct 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 - Correct Answer - Cools the motor
The amount of refrigerant that flows through the orifices of an economizer is determined by the -
Correct Answer - Difference between the high side and low side pressure
The installation of an inline refrigerant cleaning system is advisable - Correct Answer - To remove
impurities in the system
The type of refrigerant system that is least likely to leak refrigerant into the building space that are being
cooled are - Correct Answer - Indirect systems
The suction pressure of a reciprocating compressor is 65 PSIG. The discharge pressure of this
compressor is 120 PSIG. The atmospheric is 14.7PSI. the compression ratio for the given condition is
closest to: - Correct Answer - 1.69 (PSIG+14.7) Then divide both PSIG to get ratio
A superheated vappr 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 - 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 building is 55F. If the chiller is being used for human comfort, should you
be concerned about this, and why? - Correct Answer - Yes, this temperature is too high for human
comfort purpose.
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.
SOLUTIONS 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
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 condenser pressure - Correct Answer - 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 - Correct Answer - sensible and latent heat
The refrigerant unit that you have been assigned to is being taken out of service for major repair. You
have been assigned to withdraw refrigerant from storage in suitable containers. According to the NYC
fire code, you must ensure that the containers
a. do not weigh more than 200lbs when filled
b. Are approved by the US Department of Transportation (DOT)
c. are approved by the OSHA association
d. do not exceed 55 gallon in capacity - Correct Answer - Are approved by the US Department of
Transportation (DOT)
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 pistons to create less pressure - Correct 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 - Correct Answer - Cools the motor
The amount of refrigerant that flows through the orifices of an economizer is determined by the -
Correct Answer - Difference between the high side and low side pressure
The installation of an inline refrigerant cleaning system is advisable - Correct Answer - To remove
impurities in the system
The type of refrigerant system that is least likely to leak refrigerant into the building space that are being
cooled are - Correct Answer - Indirect systems
The suction pressure of a reciprocating compressor is 65 PSIG. The discharge pressure of this
compressor is 120 PSIG. The atmospheric is 14.7PSI. the compression ratio for the given condition is
closest to: - Correct Answer - 1.69 (PSIG+14.7) Then divide both PSIG to get ratio
A superheated vappr 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 - 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 building is 55F. If the chiller is being used for human comfort, should you
be concerned about this, and why? - Correct Answer - Yes, this temperature is too high for human
comfort purpose.
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.
