Z-51 Written Test Questions and Answers Fully Solved Latest Version 2025-2026
In a steam turbine, what is the function of a Kingsbury thrust bearing?
A) Maintain first stage steam pressure.
B) Compensate for coupling misalignment.
C) Adjust shaft torque at start up.
D) Maintain axial positioning of the rotor shaft. - AnswersD) Maintain axial positioning of the
rotor shaft.
The ratio of actual pressure of water pressure in the atmosphere to the saturated pressure of
given temperature is
A) partial pressure.
B) relative humidity.
C) humidity effect.
D) absolute humidity. - Answers
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 plus the heat of included non-condensable.
D) evaporator less the heat given up in the muffler. - Answers
When must the Fire Department be notified that a fire protection system is out of service?
A) The manual pull alarm station in the lobby will be out of service for 4 hours.
B) Four sprinkler heads on a same floor of your building will be out of service for 2 hours.
C) The sprinkler system will be out of service on 1st and 2nd floors.
,D) The fire alarm system is out of service in the refrigerating system room for g hours. -
AnswersC) The sprinkler system will be out of service on 1st and 2nd floors.
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. - AnswersA) 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. - AnswersC) 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. - Answers
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. - Answers
Where is emergency power not required according to code?
A) Fire pumps.
B) High rise elevators.
C) Egress illumination.
D) Data centers. - AnswersD) Data centers.
Modern compressors usually seal the rotating shaft seal as it exits the compressor housing a
spring-loaded seal made of
A) low-friction plastic.
B) rubber.
C) metal or carbon.
D) graphite-loaded fiber. - Answers
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. -
AnswersD) A S-97/S-98 Certificate of Fitness holder who is employed by a FDNY certified
company.
Which statement is correct regarding a fusible plug on a condenser?
A) The melting point is marked on it.
B) Are not allowed by code.
, C) Release refrigerant by pressure.
D) Can be back-seated. - Answers
In an office building, the display of cut natural trees (Christmas trees) is
A) never allowed.
B) allowed provided they are removed once they dry out.
C) always allowed.
D) allowed during the holiday season. - AnswersA) 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. - AnswersB) 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. - AnswersA) 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.
In a steam turbine, what is the function of a Kingsbury thrust bearing?
A) Maintain first stage steam pressure.
B) Compensate for coupling misalignment.
C) Adjust shaft torque at start up.
D) Maintain axial positioning of the rotor shaft. - AnswersD) Maintain axial positioning of the
rotor shaft.
The ratio of actual pressure of water pressure in the atmosphere to the saturated pressure of
given temperature is
A) partial pressure.
B) relative humidity.
C) humidity effect.
D) absolute humidity. - Answers
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 plus the heat of included non-condensable.
D) evaporator less the heat given up in the muffler. - Answers
When must the Fire Department be notified that a fire protection system is out of service?
A) The manual pull alarm station in the lobby will be out of service for 4 hours.
B) Four sprinkler heads on a same floor of your building will be out of service for 2 hours.
C) The sprinkler system will be out of service on 1st and 2nd floors.
,D) The fire alarm system is out of service in the refrigerating system room for g hours. -
AnswersC) The sprinkler system will be out of service on 1st and 2nd floors.
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. - AnswersA) 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. - AnswersC) 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. - Answers
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. - Answers
Where is emergency power not required according to code?
A) Fire pumps.
B) High rise elevators.
C) Egress illumination.
D) Data centers. - AnswersD) Data centers.
Modern compressors usually seal the rotating shaft seal as it exits the compressor housing a
spring-loaded seal made of
A) low-friction plastic.
B) rubber.
C) metal or carbon.
D) graphite-loaded fiber. - Answers
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. -
AnswersD) A S-97/S-98 Certificate of Fitness holder who is employed by a FDNY certified
company.
Which statement is correct regarding a fusible plug on a condenser?
A) The melting point is marked on it.
B) Are not allowed by code.
, C) Release refrigerant by pressure.
D) Can be back-seated. - Answers
In an office building, the display of cut natural trees (Christmas trees) is
A) never allowed.
B) allowed provided they are removed once they dry out.
C) always allowed.
D) allowed during the holiday season. - AnswersA) 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. - AnswersB) 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. - AnswersA) 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.
