Z-51 ACTUAL EXAM SCRIPT 2025/2026 QUESTIONS WITH
ANSWERS GRADED A+
✔✔If a sprinkler system is offline for two days, how often do you need to inspect until it
is returned to service?
A) 12-hours a day until system is restored.
B) Continuously, 24-hours a day until system is restored.
C) Only in the evening, until restored.
D) Only in the morning, until restored. - ✔✔B) Continuously, 24-hours a day until system
is restored.
✔✔Where is the muffler located?
A) After the condenser.
B) Before the compressor.
C) Between the evaporator and condenser.
D) Between the compressor and condenser. - ✔✔D) Between the compressor and
condenser.
✔✔On an operating centrifugal compressor refrigerant unit, the refrigeration engineer
notices that the compressor is short-cycling. The unit is using the low-side float valve as
a metering device. Of the following requirements, this would indicate that
A) the system is undercharged with refrigerant.
B) the system is overcharged with refrigerant.
C) an inspection should be made for a dirty and partially plugged discharge line.
D) the compressor wiring should be inspected. - ✔✔A) the system is undercharged with
refrigerant.
✔✔What should be done to prevent accidental activation of smoke detectors during hot
work operation?
A) Place fire alarm system out of service, notify the Central Watch Station and provide
fire watch.
B) Remove the batteries from the smoke detectors.
C) Cover the smoke detectors with plastic bags.
D) Inform the Central Station to ignore any fire alarm signal during the hot work
operation. - ✔✔A) Place fire alarm system out of service, notify the Central Watch
Station and provide fire watch.
✔✔Under normal conditions, the refrigerant enters the compressor as a
A) low-pressure, superheated vapor and leaves as a high-pressure vapor.
B) high-temperature vapor and leaves as a low-pressure vapor.
,C) low-pressure, superheated vapor and leaves as a high-pressure, saturated liquid.
D) low-pressure vapor and leaves as a high-pressure saturated vapor. - ✔✔A) low-
pressure, superheated vapor and leaves as a high-pressure vapor.
✔✔The total amount of heat to be removed from the refrigerant in a condenser equals
the heat picked up in the
A) evaporator plus the heat of compression.
B) evaporator.
C) evaporator less the heat given up in the muffler.
D) evaporator plus the heat of included non-condensable. - ✔✔A) evaporator plus the
heat of compression.
✔✔Which of the following requires a FDNY permit?
A) Battery system.
B) Refrigerating system.
C) Standpipe system.
D) Sprinkler system. - ✔✔B) Refrigerating system.
✔✔Which of the following is a correct statement?
A) 2.5 gallons of water weighs 10.7 lbs.
B) 2.5 gallons of water is 2.5 cubit feet.
C) 2.5 gallons of water weighs 1.05 lbs.
D) 2.5 gallons of water weighs 20.8 lbs. - ✔✔D) 2.5 gallons of water weighs 20.8 lbs.
✔✔A chilled water system uses refrigerant R134a, a leak in the evaporator shell may
result in
A) higher than normal high-side pressure.
B) a foam of ice around the point of the leak.
C) low-pressure shutdown.
D) set off the refrigerant monitor alarm. - ✔✔D) set off the refrigerant monitor alarm.
✔✔The packing gland of a centrifugal pump serves to
A) All of the answers are correct.
B) keep the air out of the pumps when the impeller housing is under negative pressure.
C) the drip part of the packing gland gives evidence that there is water in the pump.
D) keep the bearing cooled. - ✔✔C) the drip part of the packing gland gives evidence
that there is water in the pump.
✔✔The installation of an inline refrigerant cleaning system is advisable
, A) to purge non-condensables.
B) for high-pressure refrigerant systems.
C) for systems using toxic refrigerant.
D) to remove impurities from the system. - ✔✔D) to remove impurities from the system.
✔✔A refrigeration engineer is running two centrifugal water pumps in parallel. One of
the pumps is running at maximum pumping rate. If, by mistake, the refrigeration
engineer throttles back on the discharge valve of the other pump, the most likely effect
will be
A) for the pump components to maintain both the flow rate and the discharge pressure.
B) a reduction in the water pressure at the condenser inlet.
C) a reduction on the total flow rate to the condenser.
D) a reduction in both the water flow rate and pressure to the condenser. - ✔✔C) a
reduction on the total flow rate to the condenser.
✔✔When entering Phase 2 fireman's service, which statement is correct?
A) Can only be used by a firefighter.
B) Must be tested semi-annually.
C) Does not need a special key.
D) The elevator operator is the only person that could control the elevator. - ✔✔D) The
elevator operator is the only person that could control the elevator.
✔✔In a building with a multizone standpipe system, how is each zone supplied water?
A) It will supply only the highest standpipe zone.
B) Each zone will have its own automatic water supply.
C) Each zone will be connected to the main water supply.
D) It will supply only the lowest standpipe zone. - ✔✔B) Each zone will have its own
automatic water supply.
✔✔The amount of electrical power used to operate a solenoid valve or motor is
measured in
A) amperes.
B) ohms.
C) foot pounds.
D) volts. - ✔✔D) volts.
✔✔The suction service valve of a reciprocating compressor is front-seated and the
compressor runs until the low-pressure cut-out shuts the compressor off. When the
machine is off, the refrigeration engineer notices that the suction pressure increases
rapidly. The most probable cause of the pressure rise is
ANSWERS GRADED A+
✔✔If a sprinkler system is offline for two days, how often do you need to inspect until it
is returned to service?
A) 12-hours a day until system is restored.
B) Continuously, 24-hours a day until system is restored.
C) Only in the evening, until restored.
D) Only in the morning, until restored. - ✔✔B) Continuously, 24-hours a day until system
is restored.
✔✔Where is the muffler located?
A) After the condenser.
B) Before the compressor.
C) Between the evaporator and condenser.
D) Between the compressor and condenser. - ✔✔D) Between the compressor and
condenser.
✔✔On an operating centrifugal compressor refrigerant unit, the refrigeration engineer
notices that the compressor is short-cycling. The unit is using the low-side float valve as
a metering device. Of the following requirements, this would indicate that
A) the system is undercharged with refrigerant.
B) the system is overcharged with refrigerant.
C) an inspection should be made for a dirty and partially plugged discharge line.
D) the compressor wiring should be inspected. - ✔✔A) the system is undercharged with
refrigerant.
✔✔What should be done to prevent accidental activation of smoke detectors during hot
work operation?
A) Place fire alarm system out of service, notify the Central Watch Station and provide
fire watch.
B) Remove the batteries from the smoke detectors.
C) Cover the smoke detectors with plastic bags.
D) Inform the Central Station to ignore any fire alarm signal during the hot work
operation. - ✔✔A) Place fire alarm system out of service, notify the Central Watch
Station and provide fire watch.
✔✔Under normal conditions, the refrigerant enters the compressor as a
A) low-pressure, superheated vapor and leaves as a high-pressure vapor.
B) high-temperature vapor and leaves as a low-pressure vapor.
,C) low-pressure, superheated vapor and leaves as a high-pressure, saturated liquid.
D) low-pressure vapor and leaves as a high-pressure saturated vapor. - ✔✔A) low-
pressure, superheated vapor and leaves as a high-pressure vapor.
✔✔The total amount of heat to be removed from the refrigerant in a condenser equals
the heat picked up in the
A) evaporator plus the heat of compression.
B) evaporator.
C) evaporator less the heat given up in the muffler.
D) evaporator plus the heat of included non-condensable. - ✔✔A) evaporator plus the
heat of compression.
✔✔Which of the following requires a FDNY permit?
A) Battery system.
B) Refrigerating system.
C) Standpipe system.
D) Sprinkler system. - ✔✔B) Refrigerating system.
✔✔Which of the following is a correct statement?
A) 2.5 gallons of water weighs 10.7 lbs.
B) 2.5 gallons of water is 2.5 cubit feet.
C) 2.5 gallons of water weighs 1.05 lbs.
D) 2.5 gallons of water weighs 20.8 lbs. - ✔✔D) 2.5 gallons of water weighs 20.8 lbs.
✔✔A chilled water system uses refrigerant R134a, a leak in the evaporator shell may
result in
A) higher than normal high-side pressure.
B) a foam of ice around the point of the leak.
C) low-pressure shutdown.
D) set off the refrigerant monitor alarm. - ✔✔D) set off the refrigerant monitor alarm.
✔✔The packing gland of a centrifugal pump serves to
A) All of the answers are correct.
B) keep the air out of the pumps when the impeller housing is under negative pressure.
C) the drip part of the packing gland gives evidence that there is water in the pump.
D) keep the bearing cooled. - ✔✔C) the drip part of the packing gland gives evidence
that there is water in the pump.
✔✔The installation of an inline refrigerant cleaning system is advisable
, A) to purge non-condensables.
B) for high-pressure refrigerant systems.
C) for systems using toxic refrigerant.
D) to remove impurities from the system. - ✔✔D) to remove impurities from the system.
✔✔A refrigeration engineer is running two centrifugal water pumps in parallel. One of
the pumps is running at maximum pumping rate. If, by mistake, the refrigeration
engineer throttles back on the discharge valve of the other pump, the most likely effect
will be
A) for the pump components to maintain both the flow rate and the discharge pressure.
B) a reduction in the water pressure at the condenser inlet.
C) a reduction on the total flow rate to the condenser.
D) a reduction in both the water flow rate and pressure to the condenser. - ✔✔C) a
reduction on the total flow rate to the condenser.
✔✔When entering Phase 2 fireman's service, which statement is correct?
A) Can only be used by a firefighter.
B) Must be tested semi-annually.
C) Does not need a special key.
D) The elevator operator is the only person that could control the elevator. - ✔✔D) The
elevator operator is the only person that could control the elevator.
✔✔In a building with a multizone standpipe system, how is each zone supplied water?
A) It will supply only the highest standpipe zone.
B) Each zone will have its own automatic water supply.
C) Each zone will be connected to the main water supply.
D) It will supply only the lowest standpipe zone. - ✔✔B) Each zone will have its own
automatic water supply.
✔✔The amount of electrical power used to operate a solenoid valve or motor is
measured in
A) amperes.
B) ohms.
C) foot pounds.
D) volts. - ✔✔D) volts.
✔✔The suction service valve of a reciprocating compressor is front-seated and the
compressor runs until the low-pressure cut-out shuts the compressor off. When the
machine is off, the refrigeration engineer notices that the suction pressure increases
rapidly. The most probable cause of the pressure rise is
