FDNY Z51 written z51 Test Exam Recent 2025- 2026 Version Updated with All 200 Questions a, Exams of Nursing

Download FDNY Z51 written z51 Test Exam Recent 2025- 2026 Version Updated with All 200 Questions a and more Exams Nursing in PDF only on Docsity! 1 FDNY Z51 written z51 Test Exam Recent 2025- 2026 Version Updated with All 200 Questions and detailed answers 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: - CORRECT ANSWER>>Lowering the condensing pressure The heat removed from the refrigerant in a condenser is: - CORRECT ANSWER>>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 suitable containers. according to the new York city fire code, you must ensure that the containers: - CORRECT ANSWER>>Are approved by the US department of transportation Which of the following best describes how the cylinder unloader work? - 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>>Cool the motor The amount of refrigerant that flows through the orifices of a economizer is determined by the: - CORRECT ANSWER>>Difference between the high side and load side pressure The installation of an inline refrigerant cleaning system is advisable: - CORRECT ANSWER>>To remove impurities from the system The type of refrigerant system that is least likely to leak refrigerant into the building space that are cooled - CORRECT ANSWER>>The indirect system The suction pressure of a reciprocating compressor is 65PSIG. the discharge pressure of this compressor is 120PSIG. the atmospheric is 14.7 PSI. the compression ratio for the given condition is closet to: - CORRECT ANSWER>>1.69 A super heated vapor is a ? - CORRECT ANSWER>>Dry vapor above the saturation temperature 2 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>>The 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 A refrigeration engineer is logging reading from a reciprocating system. compressor discharge temperature have dropped significantly and the suction line pressure is high. which of the following that may be causing this set of condition. - CORRECT ANSWER>>An expansion valve that is open to wide A low side float valve is used to maintain: - CORRECT ANSWER>>The level of the refrigerant in the evaporator Regarding fire safety, which ASHARE refrigerant safety classification indicates no flammability and lower the toxicity? - CORRECT ANSWER>>A1 When an expansion valve is operating properly, at the end of the evaporator will contain: - CORRECT ANSWER>>Only superheated vapor 5 gallons of water do you expect to obtain if this pipe is drained completely? - CORRECT ANSWER>>440 A water chilling system uses refrigerant R123. a leak in the evaporator shell mat result in - CORRECT ANSWER>>A higher than normal high side pressure Capacitors are used on refrigeration motors. of the following, the function of these devices is to? - CORRECT ANSWER>>Store electrical charges during starting and running the motor Of the following, centrifugal refrigerant machine is best characterized by: - CORRECT ANSWER>>High volume low pressure machine Which of the following ASHRAE refrigerant safety classification is the most flammable? - CORRECT ANSWER>>A3 Which of the following correctly describes the object in the picture below? - CORRECT ANSWER>>Standpipe hose outlet to put out fires in cae of emergency Modern compressors usually seal the rotating shaft as it exits the compressor housing a spring loaded seal made of - CORRECT ANSWER>>Metal or carbon The British Thermal Unit (BTU) is the measurement of heat of energy. if 10 BTU are transferred to 10 pounds of water, the water temperature increase will be closest to: - CORRECT ANSWER>>1F A reciprocating compressor cylinder has a 10 inch bore and 14 inches stroke. the volume of refrigerant, in a cubic inches, will be closer to: - CORRECT ANSWER>>1099 An electrically operated control requires 24 volts to operate. to change the available 110 volts to 24 volts - CORRECT ANSWER>>Transformer In an indirect refrigerant system, of the following , the one that would not be used as a cooling medium for the building spaces being cooled is: - CORRECT ANSWER>>R22 refrigerant On a steam turbine, what would cause the atmospheric valve to open? - CORRECT ANSWER>>low vacuum in the surface condenser, leaking tubes in the surface condenser, dirty tubes n the surface condenser 6 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 noise, 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: - CORRECT ANSWER>>Turn on pump #2 shut off pump #1, and trouble shot pump #1 Electric devices may be used to provide built in defrosting of refrigeration machine evaporator units. these devices are classified as - CORRECT ANSWER>>Resistors The flash point of compressor lubricating oil: - CORRECT ANSWER>>Should be higher than the compression temperature The primary way of achieving capacity control of a centrifugal compressor is by; - CORRECT ANSWER>>Adjustment of the impeller inlet pre-rotation vanes Cooling tower water requires the addition of chemical additives in order to: - CORRECT ANSWER>>Reduce the formation of scale and algae In the picture below describe the equipment's function? - CORRECT ANSWER>>Remove non condensable from the condenser the viscosity of lubrication oil is described by a number. a low viscosity number describes oil that: - CORRECT ANSWER>>Flows easily The most likely reason for a refrigeration engineer to use a psychrometer is to measure - CORRECT ANSWER>>Relative humidity level of the atmosphere The most important reason to use at least two compressors in a cascade system is to: - CORRECT ANSWER>>Avoid 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: - CORRECT ANSWER>>Malfunction of a compressor valve Regarding the functioning of a steam turbine, why is it advisable to keep moisture in the inlet low as possible? - CORRECT ANSWER>>Keeps turbine blades wear to minimum 7 According to the attached Material Safety Data Sheet (MSDS) R134 is a - CORRECT ANSWER>>Clear, odorless liquid and vapor Under normal condition, the refrigerant enters the compressor as a: - CORRECT ANSWER>>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 : - CORRECT ANSWER>>Sudden drop in the crankcase pressure Assume that an engineer is able to observe refrigerant water and oil together. the fluids would settle in the container from top to bottom: - CORRECT ANSWER>>Oil, water, refrigerant What is the function of the vacuum breaker in a steam turbine. - CORRECT ANSWER>>To achieve a faster coast down cycle An equalizer line on a TXV is used to: - CORRECT ANSWER>>Compensate for the pressure drop across the evaporator coil If R134 accidentally touches a refrigerant engineer's skin, what first aid should be applied from the MSDS? - CORRECT ANSWER>>Promptly flush skin with water until all chemical is removed In a multi stage centrifugal compressor, each stage: - CORRECT ANSWER>>Is identical in volume to the other stages 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 high. of the following the one that may causing this set condition. - CORRECT ANSWER>>Faulty compressor valves On an operating centrifugal compressor refrigerant unit, the refrigeration engineer notices that the compressor is short cycling. the unit is using low side float valve as a metering device. of the following requirements this would indicate that: - CORRECT ANSWER>>The system is undercharged with refrigerant The vessel depicted below may used in connection with - CORRECT ANSWER>>Refrigerant recovery 10 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: - CORRECT ANSWER>>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: - CORRECT ANSWER>>An electrical current creating a magnetic field The process by which refrigerant is extracted and cleaned for reuse without requirements for reclamation is called - CORRECT ANSWER>>Recycle A Centrifugal compressor is in operation with suction pressure is 3 psig and the discharge is 10 psi what is the atmospheric pressure 14.7 which is the ratio to: - CORRECT ANSWER>>1.39 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. the panel display on the refrigeration system indicates that the problem is water flow. what do you do? - CORRECT ANSWER>>Check the condenser water pump and restart the refrigeration system Electrical current is measured in? - CORRECT ANSWER>>Amperage How would you put an additional pump online? - CORRECT ANSWER>>Open suction valve, open discharge valve gradually Of the following, the major advantage of a shell and coil condenser is: - CORRECT ANSWER>>There is less dangers of developing leaks An engineer needs to vary the flow of refrigerant in a refrigeration system. which operation in the flow of the system does not include: - CORRECT ANSWER>>Solenoid valve thermal bulb is attached to the suction pipe between the evaporator coil and the compressor by an insulated line. assume that the machinery room is at 85F. break down of the insulation results in: - CORRECT ANSWER>>Flood the evaporator A chill water system uses refrigerant R134 a leak in the evaporator shell may result in: - CORRECT ANSWER>>Set off the refrigerant monitor alarm 11 What are steam ejector used for on the surface condenser of a system with a turbine: - CORRECT ANSWER>>To create a proper opening exhaust system Water and moisture is serious problem in a refrigerant system how to avoid: - CORRECT ANSWER>>Proper evacuation at the charging of the system The most important requirements for a good evaporator is that: - CORRECT ANSWER>>It must have enough cooling surface to absorb the required heat While on duty a refrigeration engineer notice that the suction line to the compressor and part of the compressor itself is frosted of the following, the most likely reason for this condition would be: - CORRECT ANSWER>>There is not enough refrigerant in the system While doing a routine line inspection, the engineer notices the bulb of the TXV on the floor refrigerant engineer should attach bulb at the : - CORRECT ANSWER>>The outlet end of the coil To convert water 32F to ice at the same temperature a refrigeration system must remove: - CORRECT ANSWER>>The latent heat of fusion The use of oil in the refrigeration machine is to: - CORRECT ANSWER>>Reduce wear and friction in the compressor parts The following is a desirable property in a refrigeration - CORRECT ANSWER>>High latent heat The cooling medium for an evaporative condenser is: - CORRECT ANSWER>>Air and water The ratio of the actual pressure of water vapor in the atmosphere to the saturated pressure of give temperature is: - CORRECT ANSWER>>Relative humidity The only refrigerant/ temperature chart available to a refrigerant engineer list the temperature is degrees Celsius if the chart indicates a Celsius temperature of 4 degrees to equivalent to F: - CORRECT ANSWER>>39.2 degrees A refrigerant engineers was instructed to charge of 60 ton plant with R134A refrigerant. the refrigerant engineer will most likely find the charging valve on the - CORRECT ANSWER>>Low pressure side of the system 12 A refrigerant engineer verifies that a chilled water pump is cavitating. of the following the most likely cause for this condition is: - CORRECT ANSWER>>Water leaks through the mechanical seals There is a decrease in the efficiency of a reciprocating compressor. this most likely caused by: - CORRECT ANSWER>>Leaking suction valve The suction and discharge valve of the reciprocating compressor are mounted as follows: - CORRECT ANSWER>>Discharge valves on top of the valve plate and suction valve below 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 your rounds you notice that the discharge pressure of your condenser water pumps is significantly lower than normal. which of the following action would you avoid taking: - CORRECT ANSWER>>Put on an additional surface condenser pump and lower the chilled water set point A water pump is discharge against head 92 feet of water, this is approximately to a pressure of: - CORRECT ANSWER>>40 psi Which of the following will connect to the middle port on a gauge manifold? - CORRECT ANSWER>>Vacuum pump The most important reason for installing a muffler in a reciprocating refrigerant machine is: - CORRECT ANSWER>>To contain the compressor pulsation noise Of the following, the statement that most accurately characterize a hermetic compressor is that it: - CORRECT ANSWER>>Will have both the compressor and motor enclosed is gas tight housing In the picture the valve is in what position (45 degree angle to the left) - CORRECT ANSWER>>The valve is crack open What is the order of components on the liquid line of a reciprocating system from the condenser to the TEV? - CORRECT ANSWER>>King valve, filter drier, solenoid valve, sight glass A high-side float valve is used to maintain: - CORRECT ANSWER>>Constant level of refrigerant in the evaporator 15 Why is refrigerant gauge called a compound gauge? - CORRECT ANSWER>>It reads positive pressure and vacuum Which of the following does not require flame resistant treatment? - CORRECT ANSWER>>ART work in a museum An engineer observes a gauge that reads saturation pressure of a refrigerant. if chilled water s circulate as the cooling medium this reading best be used to estimate the? - CORRECT ANSWER>>Temperature of chilled water being pumped to the space being cooled Regardless of the ASHRAE refrigerant classification in use, in the event of a refrigerant escape the engineer should be aware of? - CORRECT ANSWER>>Asphyxiation What type of refrigerant is found inside the machines Gauges? - CORRECT ANSWER>>Same type of refrigerant inside the machine If resistance is cut in half, what happens to the power factor? - CORRECT ANSWER>>Increases by a factor of two What are pre hot works procedures performed prior to hot works? - CORRECT ANSWER>>Check area once a day leading up to hot works A chilled water system has an air cooled condensing unit on a roof during cold weather ha what type of protection? - CORRECT ANSWER>>Air limiting device What is a compressor safety head? - CORRECT ANSWER>>A spring on the valve plate Stand pipe certificate should be available for? - CORRECT ANSWER>>FDNY and building inspector When is a chemical fire extinguisher system needed? - CORRECT ANSWER>>Where water is not sufficient What is most accurate about fire alarm books? - CORRECT ANSWER>>Must be kept in the fire alarm panel What is the volume of a box 12" x12" x12" measure? - CORRECT ANSWER>>1 cubic foot 16 A condenser pump is supplied with 85 degree water from a cooling tower and returns to the tower at 88 degrees engineer is sure the condenser tubes are clean and free of obstructions. the condenser has high condenser pressure. the reason for this could be? - CORRECT ANSWER>>Over charge of refrigerant Fireproof decorations n buildings is useful for? - CORRECT ANSWER>>Don't catch fire in an emergency What is the lowest temperature a cooling tower can be? - CORRECT ANSWER>>Wet bulb temperature Manifold hoses should be equipped with? - CORRECT ANSWER>>Low loss fittings Water regulating valves are used to? - CORRECT ANSWER>>Maintain condenser pressure to pre-determined level What type of sprinkler system needs inspecting? - CORRECT ANSWER>>Automatic You are performing hot works near a sprinkler head. what can you do to prevent the fire alarm from going off? - CORRECT ANSWER>>Take the building offline How long does it take to warm up a steam turbine? - CORRECT ANSWER>>10-15 minutes Why is a pressure relief valve better that a fusible plug? - CORRECT ANSWER>>Minimizes refrigerant loss What is the state of refrigerant entering the compressor on a reciprocating machine? - CORRECT ANSWER>>Superheated vapor In the absence of water chemical treatment of a cooling tower? - CORRECT ANSWER>>Drain tower every one to two weeks & replace with fresh water What is ammonia's refrigerant ASHRAE classification? - CORRECT ANSWER>>B2 What is the function of a safety head on a compressor? - CORRECT ANSWER>>Prevents liquid slugging from damaging the valve plate 17 What does a wiring diagram display? - CORRECT ANSWER>>Wiring of components Filter driers remove - CORRECT ANSWER>>Moisture and particles Show a picture of an insulated pump and ask what is this pump? - CORRECT ANSWER>>Centrifugal chill water pump IF 29.92'HG is equal to 14.7 Psia then 26"HG converts to what in Psia? - CORRECT ANSWER>>12.77 When charging refrigerant on the low side of a reciprocating machine with manifold gauges, what is the position of the manifold? - CORRECT ANSWER>>High side frontseated low side backseated 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. you are supplying 46 degree chilled water. all the buildings are satisfied except one building. what action should the engineer do? - CORRECT ANSWER>>Put an additional chilled water pump online The cooling medium for a cooling tower is? - CORRECT ANSWER>>Air The charge in a TEV sensing bulb is? - CORRECT ANSWER>>Similar to refrigerant in system When you finished leak testing with R22 and nitrogen the next step should be? - CORRECT ANSWER>>Vent refrigerant and nitrogen to open air What is the device used to measure the speed of a turbine? - CORRECT ANSWER>>Tachometer The condenser pump is on the first floor and not running. the pressure gauge shows 55 psi. there is 15 feet for each floor. what floor is the cooling tower on? - CORRECT ANSWER>>8 There is 7.48 gallons per cubic foot. how many gallons of water are in a pipe 8 feet in diameter and 10 feet long? - CORRECT ANSWER>>3758 A technician had been asked to estimate the cost of operating a 5 horse power motor. because the plant is build by energy consumed as kiliowatt-hours, the technician will have to calculate