Z-51
Z-51 WRITTEN TEST EXAM QUESTIONS
AND ANSWERS UPDATED
(2025/2026)
Hot work authorizations are issued by
A) a Responsible Person designated by the Building Owner.
B) a Building Department inspector.
C) a FDNY inspector.
D) the Building owner's insurance company. ANSWERA) a Responsible
Person designated by the building owner.
Insecticidal fogging operations are hazardous because chemicals
A) are corrosive.
B) are water-reactive.
C) may be toxic.
D) are highly unstable. ANSWERC) may be toxic.
What is a compressor safety head?
A) Rupture disc.
B) A pressure relief valve on the low side.
C) Cylinder head with a low pressure relief on the high side.
D) A spring on the valve plate. ANSWER
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The oil collected in an oil separator is generally
A) caused by an oil overcharge.
B) returned to the compressor.
C) filtered and returned to the compressor.
D) drained and replaced by fresh oil. ANSWER
Where is emergency power not required according to code?
A) Fire pumps.
B) High rise elevators.
C) Egress illumination.
D) Data centers. ANSWERD) Data centers.
A technician shows up to service the fire alarm panel in your building. What
COF qualifications must he/she have?
A) A Q-01/Q-99 Certificate of Qualification holder who is designated by the
building owner.
B) A certified Fire Safety Director who is designated by the building owner.
C) A S-95 Certificate of Fitness holder who is employed by a FDNY certified
company.
D) A S-97/S-98 Certificate of Fitness holder who is employed by a FDNY
certified company. ANSWERD) A S-97/S-98 Certificate of Fitness holder who is
employed by a FDNY certified company.
In an office building, the display of cut natural trees (Christmas trees) is
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A) never allowed.
B) allowed provided they are removed once they dry out.
C) always allowed.
D) allowed during the holiday season. ANSWERA) never allowed.
Describe the equipment's function in the picture.
A) Control flow of refrigerant to the compressor.
B) Remove non-condensable from the condenser.
C) Relieve excess pressure from the condenser.
D) Relieve excess pressure from the evaporator. ANSWERB) Remove non-
condensable from the condenser.
When the expansion valve is operating properly, the end of the evaporator
will contain
A) only superheated vapor.
B) saturated liquid refrigerant
C) only vapor.
D) only liquid refrigerant. ANSWERA) only superheated vapor.
How much extra refrigerant con be stored in a machine room?
A) 330 lbs.
B) The amount equal to the design pressure.
C) 20% above normal charge.
D) 220 lbs. ANSWERC) 20% above normal charge.
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A refrigeration compressor has failed to turn on. The refrigeration
engineer on duty verifies that the electrical circuit to the motor, including
all switches and circuit breakers, is complete according to recommended
service practice. The next item to be checked would likely by the
A) temperature and pressure controls.
B) refrigerant charge.
C) cooling tower operation.
D) liquid-line solenoid valve. ANSWERA) temperature and pressure controls.
The use of oil in the refrigeration machine is to
A) Add non-condensates to refrigerant.
B) Mix the oil with liquid refrigerant.
C) Reduce wear and friction in compressor parts.
D) None of the answers are correct. ANSWERC) Reduce wear and friction in
compressor parts.
The heat removed from the refrigerant condenser is
A) latent heat only.
B) sensible heat only.
C) sensible and latent heat.
D) Radiant heat only. ANSWERC) sensible and latent heat.
Which service valve should be installed in a dual pressure release valve
while keeping system in service?
A) Two-way valve.
B) Plug valve.
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Z-51 Written
Z-51 WRITTEN TEST EXAM QUESTIONS
AND ANSWERS UPDATED
(2025/2026)
Hot work authorizations are issued by
A) a Responsible Person designated by the Building Owner.
B) a Building Department inspector.
C) a FDNY inspector.
D) the Building owner's insurance company. ANSWERA) a Responsible
Person designated by the building owner.
Insecticidal fogging operations are hazardous because chemicals
A) are corrosive.
B) are water-reactive.
C) may be toxic.
D) are highly unstable. ANSWERC) may be toxic.
What is a compressor safety head?
A) Rupture disc.
B) A pressure relief valve on the low side.
C) Cylinder head with a low pressure relief on the high side.
D) A spring on the valve plate. ANSWER
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The oil collected in an oil separator is generally
A) caused by an oil overcharge.
B) returned to the compressor.
C) filtered and returned to the compressor.
D) drained and replaced by fresh oil. ANSWER
Where is emergency power not required according to code?
A) Fire pumps.
B) High rise elevators.
C) Egress illumination.
D) Data centers. ANSWERD) Data centers.
A technician shows up to service the fire alarm panel in your building. What
COF qualifications must he/she have?
A) A Q-01/Q-99 Certificate of Qualification holder who is designated by the
building owner.
B) A certified Fire Safety Director who is designated by the building owner.
C) A S-95 Certificate of Fitness holder who is employed by a FDNY certified
company.
D) A S-97/S-98 Certificate of Fitness holder who is employed by a FDNY
certified company. ANSWERD) A S-97/S-98 Certificate of Fitness holder who is
employed by a FDNY certified company.
In an office building, the display of cut natural trees (Christmas trees) is
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A) never allowed.
B) allowed provided they are removed once they dry out.
C) always allowed.
D) allowed during the holiday season. ANSWERA) never allowed.
Describe the equipment's function in the picture.
A) Control flow of refrigerant to the compressor.
B) Remove non-condensable from the condenser.
C) Relieve excess pressure from the condenser.
D) Relieve excess pressure from the evaporator. ANSWERB) Remove non-
condensable from the condenser.
When the expansion valve is operating properly, the end of the evaporator
will contain
A) only superheated vapor.
B) saturated liquid refrigerant
C) only vapor.
D) only liquid refrigerant. ANSWERA) only superheated vapor.
How much extra refrigerant con be stored in a machine room?
A) 330 lbs.
B) The amount equal to the design pressure.
C) 20% above normal charge.
D) 220 lbs. ANSWERC) 20% above normal charge.
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A refrigeration compressor has failed to turn on. The refrigeration
engineer on duty verifies that the electrical circuit to the motor, including
all switches and circuit breakers, is complete according to recommended
service practice. The next item to be checked would likely by the
A) temperature and pressure controls.
B) refrigerant charge.
C) cooling tower operation.
D) liquid-line solenoid valve. ANSWERA) temperature and pressure controls.
The use of oil in the refrigeration machine is to
A) Add non-condensates to refrigerant.
B) Mix the oil with liquid refrigerant.
C) Reduce wear and friction in compressor parts.
D) None of the answers are correct. ANSWERC) Reduce wear and friction in
compressor parts.
The heat removed from the refrigerant condenser is
A) latent heat only.
B) sensible heat only.
C) sensible and latent heat.
D) Radiant heat only. ANSWERC) sensible and latent heat.
Which service valve should be installed in a dual pressure release valve
while keeping system in service?
A) Two-way valve.
B) Plug valve.
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