Download FDNY Z51 Actual Exam 2025/2026: Refrigeration Systems Questions and Answers and more Exams Refrigeration and Air Conditioning in PDF only on Docsity!
FDNY Z51 ACTUAL EXAM 2025/2026|ACTUAL 220
EXAM Qs &As|LATEST UPDATE 2025 SPRING|A+
GRADE PASS
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: - ANS:->>>>Lowering the condenser pressure The heat removed from the refrigerant in a condenser is: - ANS:->>>>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: - ANS:->>>>approved by us department of transportation Which of the following best describes how the cylinder unloader work? - ANS:-
Keep in the suction valve opened while the compressor is in return stroke. In most semi Hermetic compressors, the suction vapor is used to:
The amount of refrigerant that flows through the orifices of a economizer is determined by the: - ANS:->>>>Difference between high and low side pressure The Installation of an Inline refrigerant cleaning system is advisable: - ANS:->>>>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: - ANS:->>>>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: - ANS:->>>>1.69 Discharge/suction A superheated vapor is a: - ANS:->>>>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: - ANS:->>>>A faulty cooling tower water level controller A centrifugal water pump is known as a lift pump when the: - ANS:->>>>The water
evaporator Regarding fire safety, which ASHRAE refrigerant safety classification Indicates no flammability and lower toxicity? - ANS:->>>>A When an expansion valve is operating property, af the end of the evaporator will contain: - ANS:->>>>Only superheated vapor What Information is not contained in a Material Safety Data Sheet-MSD5? - ANS:->>>>Cost of material In a steam turbing, what is the function of the Kingsbury thrust bearing - ANS:-
Maintain first stage steam pressure A centrifugal water pump is considered to be fully primed when - ANS:->>>>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 - ANS:->>>>Lever type tubing bender A reciprocating compressor is making a knocking sound during operation. If the
refrigerant worn parts are not causing the knocking, what is probably the cause - ANS:-
The slugging of liquid refrigerant In order for a refrigerant to become superheated it must be heated in a section of the low side refrigerant line: - ANS:->>>>Where no liquid refrigerant is located All liquid has been recovered from a system to be overhauled, the system - ANS:- Should not be opened untill all vapor is recovered The water evaporator Regarding fire safety, which ASHRAE refrigerant safety classification Indicates no flammability and lower toxicity? - ANS:->>>>A When an expansion valve is operating property, af the end of the evaporator will contain: - ANS:->>>>Only superheated vapor What Information is not contained in a Material Safety Data Sheet-MSD5? - ANS:->>>>Cost of material In a steam turbing, what is the function of the Kingsbury thrust bearing - ANS:- >>>>Maintain first stage steam pressure A centrifugal water pump is considered to be fully primed when - ANS:->>>>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 - ANS:->>>>Lever type tubing bender A reciprocating compressor is making a knocking sound during operation. If the refrigerant worn parts are not causing the knocking, what is probably the cause - ANS:- >>>>The slugging of liquid refrigerant In order for a refrigerant to become superheated it must be heated in a section of the low side refrigerant line: - ANS:->>>>Where no liquid refrigerant is located All liquid has been recovered from a system to be overhauled, the system - ANS:- >>>>Should not be opened untill all vapor is recovered When a refrigerant engineer uses a portable compressor recovery unit to remove vapor refrigerant from a refrigeration system the removal rate of the refrigerant will gradually slow down because - ANS:->>>>The vapor density is decreasing You are the engineer running a 2000-ton (steam-driven turbine) contrifugal refrigeration system, a refrigeration system supplies chilled water to a college campus with multiple bulldings. During the course of making your rounds, you check the 9 cell cooling tower on the roof. You note the water level in all of the cooling tower cells is very low. Which one of the following Immediate action would take? - ANS:- Add additional make up water to cooling tower A rooftop water cooling tower is connected to a water pump in the building
Refrigerant recycling
Information about the physical and chemical properties of a hazardous material can be found in: - ANS:->>>>Material safety data sheet What is the function of the turbine auxillary oil pump? - ANS:->>>>Establish oil pressure during turbine startup The rupture disc for a low pressure centrifugal refrigeration machine is normally located on the: - ANS:->>>>Compressor suction What is the primary reason ribbed metal piping is used for electrical wires connected to the refrigeration system shown below? - ANS:->>>>Allows for flexibility and accounts for vibration A multi- cylinder reciprocating compressor uses cylinder unloaders to regulate capacity, what would not occur if some of the unloaders fail to operate when needed? - ANS:->>>>The chilled water temp will increase As shown In the picture below, the suction gauge of a condenser water pump reads 55 PSI. The pipe supplying the pump is 75 feet long and 12 inches in diameter. approximately how many gallons of water do you expect to obtain if this pipe is drained completely?
- ANS:->>>>1 degrees F A reciprocating compressor cylinder has a 10 Inches bore and 14 Inches stroke. The volume of refrigerant, in cubic inches, will be closer to: - ANS:->>>>
- An electrically operated control requires 24 volts to operate. to change the available 110 volts to 24 volts - ANS:->>>>Transformer In an indirect refrigeration system of the following, the one that would not be used as a cooling medium for the building spaces being cooled is: - ANS:->>>>R refrigerant On a steam turbine, what would cause the atmospheric valve to open? - ANS:->>>>All answers are correct
- low vacuum in the surface condenser
- leaking tubes in the surface condenser
- dirty tubes in the surface condenser You are the engineer running a 2000-ton (steam-driven turbine) centrifugal refrigeration system, a refrigeration system supplies chilled water to a college campus with multiple buildings. making your rounds, you notice that condenser water
pump#1 is making a lot of nolse, the discharger gauge reading of the condenser water pump is fluctuating drastically, and motor of the condenser pump #1 is running very hot. Which of the following actions would you take: - ANS:->>>>Turn of pump 2 turn of pump 1 troubleshoot pump 1
The most important reason to use at least two compressors in a cascade system is to: - ANS:->>>>Avoid a very high compression ratio for each compressor The suction service valve of a reciprocating compressor is front seated and the compressor runs until the low pressure cut-out shut the compressor off. When the machine is stopped, the refrigeration engineer notices that the suction pressure increase rapidly. The most probable cause of this pressure rise: - ANS:-
Malfunction of compressor valve Regarding the functioning of a steam turbine, why is it advisable to keep moisture in the inlet low as possible? - ANS:->>>>Keeps turbine blades wear to a minimal All answers are correct - low vacuum in the surface condenser - leaking tubes in the surface condenser - dirty tubes in the surface condenser You are the engineer running a 2000-ton (steam-driven turbine) centrifugal refrigeration system, a refrigeration system supplies chilled water to a college campus with multiple buildings. making your rounds, you notice that condenser water pump#1 is making a lot of nolse, the discharger gauge reading of the condenser water pump is fluctuating drastically, and motor of the condenser pump #1 is running very hot. Which of the following actions would you take: - ANS:->>>>Turn of pump 2 turn of pump 1 troubleshoot pump 1 The most important reason to use at least two compressors in a cascade system is to: - ANS:->>>>Avoid a very high compression ratio for each compressor The suction service valve of a reciprocating compressor is front seated and the compressor runs until the low pressure cut-out shut the compressor off. When the machine is stopped, the refrigeration engineer notices that the suction pressure increase rapidly. The most probable cause of this pressure rise: - ANS:- >>>>Malfunction of compressor valve Regarding the functioning of a steam turbine, why is it advisable to keep moisture in the inlet low as possible? - ANS:->>>>Keeps turbine blades wear to a minimal According to the attached Material Safety Data Sheet (MISDS) R134 is a - ANS:- Clear, odorless liquid and vapor Under normal condition, the refrigerant enters the compressor as a: - ANS:->>>>Low pressure superheated vapor and leaves as a high pressure vapor While operating an R-22 single acting compressor system, the refrigeration engineer noticed oil foaming in the crankcase. This condition most likely, would have been caused by a: - ANS:->>>>Sudden drop in the crankcase pressure
Assume that an engineer is able to observe refrigerant water and oil together. The flulds would settle in the container from top to bottom: - ANS:->>>>Oil, water, refrigerant What is the function of the vacuum breaker In a steam turbine. - ANS:->>>>To achieve a faster coast down cycle An equalizer line on a TV is used to: - ANS:->>>>Compensate for a pressure drop across the evaporator coil. If R134 accidentally touches a refrigerant engineer's skin, what first aid should be applied from the MISDS? - ANS:->>>>Promptly flush skin with water untill all chemical is removed In a multi stage centrifugal compressor, each stage: - ANS:->>>>Has smaller volume than the one before it A refrigeration engineer notices excessive cycling of the temperature control for a reciprocating compressor refrigeration unit. The crankcase temperature is high, the compressor discharge temperature low, the suction line temperature is high. of the following the one that may causing this set of condition. - ANS:->>>>Faulty compressor valves
following requirements this would Indicate that: - ANS:->>>>The system is undercharged with refrigerant The vessel depicted below may used in connection with - ANS:->>>>Recovery tank A refrigeration system uses jet ejector to raise settled oil mixed with refrigerant to the oil pump. If a restriction in the refrigerant flow to the jet ejector develops: - ANS:->>>>There may be insufficient head to lift the oil An indirect low temperature refrigerant system frequently uses glycol, instead of salt brine, as the intermediate cooling medium. an advantage of this choice is: - ANS:-
The elimination of corrosion In relation to the suction pressure of a compressor, the reading on the oil pressure gauge should read in the range, closer to; - ANS:->>>>15 to 30 psi higher Non- condensable gases like air, oil vapor, or nitrogen travel through a refrigerant system with the refrigerant they usually accumulate in the: - ANS:- Condenser
The advantage of forced draft cooling tower over natural draft cooling towers is: - ANS:->>>>Smaller tower size The sole refrigeration engineer on duty in a building is permitted to leave the building refrigeration system when it is in operation only when: - ANS:->>>>Relieved by another licensed refrigeration engineer A system controlled by a TXV show high discharge pressure and high normal sub- cooling. The cause is most probably a: - ANS:->>>>Refrigerant overcharge Which of following Is a correct statement? - ANS:->>>>2.5 gallons of water weighs 20. pounds Liquid level gauge glasses (except the bull's eye) are generally equipped with: - ANS:-
Manual and automatic closing shutoff valves Copper and aluminum are frequently used for condenser tubes in refrigeration system. these metals are used because of their. - ANS:->>>>High heat transfer coefficient Assume that a refrigeration engineer has a choice of four valves to select from.
condenser The total amount of heat to be removed from the refrigerant in a condenser equals the heat picked up in the: - ANS:->>>>Evaporator plus the heat of compression The amount of electrical power used to operate a solenoid valve or a motor is measured in: - ANS:->>>>Volts Of the following, the most common metering device used today In reciprocating commercial refrigeration system under three tons capacity is: - ANS:->>>>TEV
The purpose of wear rings in a centrifugal pump is to: - ANS:->>>>Prevent wearing of the pump housing and impellers You are the engineer running a 2000 - ton (steam-driven turbine) centrifugal refrigeration system, a refrigeration system supplies chilled water to a college campus with multiple buildings. While making rounds, you notice that the condenser water coming back down from the 9-cell cooling tower on the roof is at a temperature of 90F. You want to make a adjustment to bring the temperature of the condenser water down to 85F. Which one of the following immediate actions would you take? - ANS:->>>>Increase speed of the cooling tower fans A water chiller is equipped with a reciprocating compressor, a thermostatic expansion valve and an air cooled condenser. A restriction in the refrigerant liquid line would result in: - ANS:->>>>High suction superheat A solenoid valve is used to allow a reciprocating refrigeration machine to adapt to the load on the system. The opening of the solenoid valve is caused by: - ANS:->>>>An electrical current creating a magnetic field The process by which refrigerant is extracted and cleaned for reuse without requirements for reclamation is called - ANS:->>>>Recycle
