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Download Refrigerant Cycle and Compressor Exam Questions and more Exams Refrigeration and Air Conditioning in PDF only on Docsity!
WRITTEN Z51 TEST EXAM RECENT 2024-
2025 VERSION
The efficiency of the refrigerant cycle is affected by the operation of the condenser. of the Questions following. a more efficient centrifugal compressor operation results from: - ANSWER-Lowering the condensing pressure The heat removed from the refrigerant in a condenser is: - 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 Lo wilhdraw refrigerant for slorage in suilable containers. according to the new York city fire code, you must ensure that the containers: - ANSWER-Are approved by the US department of transportation Which of the following best d suction valve opened while the cribes how the cylinder unloader work? - ANSWEF-Keep in the compressor is in the return stroke In most semi hermetic compressors, the suction vapor is used to: - ANSWER-Cool the motor The amount of refrigerant that flows through the orifices of a economizer is determined by the: - ANSWER-Difference between the high side and load side pressure The installation of an inline refrigerant cleaning system is advisable: - 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 - ANSWER-The indirect syste The suction pressure of a reciprocating compressor is 63PSIG. the discharge pressure of this compressor is 120PSIG. the atmospheric is 14.7 PSI. the compression ratio for the given condition is closet to: - ANSWER-1.69 A super heated vapor is a ?- ANSWER-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: - ANSWER-A faulty cooling tower water level controller A centrifugal water pump is known as a lift pump when the: - ANSWER-The water supply to the pump suction inlet is below the pump level A TXYV is used Lo maintain constant: - ANSWER-Evaporalor supcrhcat The chilled water supply Lo the building is 55F. if the chiller is being used for human comfort, should you be concered about this , and why? - ANSWER Yes, this temperature is too high for human comfort purpose The packing gland of a centrifugal pump serves to: - 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 - ANSWER-Operation of the hot gas bypass valve 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 - ANSWER-Lever type tubing bender Ar parle iprocating compressor is making a knocking sound during operation. if the refrigerant worn arc nol causing Lhe knocking, what is probably the cause - ANSWER-The slugging of the liquid refrigerant In order for a refrigerant to become superheated in a section of the lowside refrigerant line: - ANSWEFR-Where no liquid refrigerant is present All quid has been recovered from a system Lo be overhauled, the systom - ANSWER-Should not. be opened until all vapor has been removed 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 - ANSWER-The vapor density is decreasing 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. During the course of making your rounds, you check the 9 ecll cooling Lower on the rool. You nale the water level in all of the cooling tower cells is very low. Which one of the following immediate action would take? - ANSWER_Add addilional make up water Lo cooling lower A rooftop water cooling tower is connccled to a water pump in the building basement with a 12 inches diameter pipe. with the pump turn off, a pressure gauge at the pumps inlet show a pressure of 140 PSIG the height of the water column, in feet, would be closet to. - ANSWER-323 > protects the steam turbine from ex °- ANSWER-governor assembly sration 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 be the: - ANSWER-Temperature and pressure controls Refrigerants are characterized by their physical properties included flash point, refrigeration effect, and others. of the refrigerant in commercial and industrial the highest latent hear and refrigerant effect is:- ANSWER-Ammonia On what characteristics is ASHRAE refrigerant safety group classification system: - ANSWER- Flammability and toxicity Of the following, and example of an in-line refrigerant cleaning system that may be used with a - ANSWER Refrigerant r centrifugal compressor containing R123 refrigerant sling Information about the physical and chemical properties of a hazardous material can be found in: - ANSWER Material Safety Data Sheet What is the function of the turbine auxiliary oil pump?- ANSWEF-Establish oil pressure during turbine start up The rupture dise for a low-pressure centrifugal refrigeration machine is normally located on the: - ANSWER-Compressor suction What is the primary reason ribbed metal piping is used for electrical wircs connected Lo the refrigeration system shown below? - ANSWER-It allows for flexibility and accounts for vibrations 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: - 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: - ANSWER-1099 An electrically operated control requires 24 volts to operate. to change the available 110 volts to 24 volts - 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: - ANSWER-R22 refrigerant Ona steam turbine, what would cause the atmospheric valve to open? - ANSWER-low vacuum in the surface condenser, leaking lubes in the surface condenser, dirty tubes n 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 noise, the discharger gauge reading of the condenser water pump is fluctuating drastically, and motor of the condenser pump #1 is running very hol. which of the following actions would you take: - ANSWER-Tum on pump #2 shut off pump #1, and trouble shot pump #1 s may be used to provide built in defrosting of refrigeration machine evaporator ified as - ANSWER-Resistors Electric dev. unils. hese devices are clas The flash point of compressor lubricaling oil: - ANSWER-Should be higher than the compression temperature The primary way of achieving capacity control of a centrifugal compressor is by; - ANSWER- Adjustment of the impeller inlet pre-rotation vanes Cooling tower water requires the addition of chemical additives in order to: - ANSWER-Reduce the formation of scale and algae In the picture below describe the equipment’s function? - ANSWER-Remove non condensable from the condenser the viscosity of lubrication oil is described by a number. a low viscosity number describes oil that: - ANSWER-Flows easily The most likely reason for a refrigeration engineer to use a psychrometer is to measure - ANSWER-Rolalive inunidity level of the alimosphere The most important reason Lo use al least wo compressors in a cascade syslom is Lo: - 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: - ANSWER-Malfanction of a compressor valve Rogarding the finctioning of a stcam turbine, why is it advisable Lo keep moisture in Lhe inlet low as possible? - ANSWER-Keeps turbine blades wear to minimum According to the attached Material Safety Data Sheet (MSDS) R134 is a- ANSWER Clear, odorless liquid and vapor 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: - ANSWER-The system is undercharged with refrigerant, The vessel depicted below may used in connection with - ANSWEF-Rolrigcrant recovery sttled oil mixed with refrigerant to the oil pump jector develops: - ANSWER-There may be A refrigeration system uses jet ejector to raise ifa restriction in the refrigerant flow to the je insufficient head to lift the oil Load of salt. brine, Lom frequently us: An indircet ow Lomperature refrigerant the intermediate cooling medium. an advantage of this choice is:- ANSWER-The elimination of corrosion Tn relation to the suction pressure of a compressor, the ding on the oil pressure gauge should read in the range, closer to:- ANSWER-15 to 30 PSI Higher Non- condensable gases like air, oil vapor, or nitrogen travel through a refrigerant system with - ANSWER-Condenser the refrigerant they usually accumulate in the: The advantage of forecd draft cooling Lower over natural drafi cooling Lower is: - ANSWER. Smaller tower size The sole refrigeration engineer on duty ina building is permitted to leave the building m when it is in operation when: - ANSWER-Relieved by another li refrigeration engineer refrigeration s Asystem controlled by a TXV show high discharge p cause is most probably a: - ANSWER-Refrig Which of the following is a correct. statement?- ANSWER25 gallons of water weighs 20.8 pounds Liquid le Automatic shut-off valves only gauge glasses (except the bull’s eye) are generally equipped with: - ANSWER- Copper and aluminum are frequently used for condenser tubes in refrigeration system. these metals are used because of their: - ANSWER-High heat transfer coefficient. Assume that a refrigeration engineer has a choice of four valves to select from. which of the ANSWER-Plig valvo following is the most effective lype af valve to control pressure Where must the material safcly data sheel. be located? - ANSWER-Where available Lo all employees The oil collected in an oil separator is generally: - ANSWE-Returmed to the compressor What is the function of the gland steam? - ANSWER-Seal the turbine rotor carbon rings Regarding the functioning of steam turbine, how is the water level controlled in the surface condenser hot well? - ANS WER-Operation of the recirculation and overboard valves The cause of a starved evaporator might be: - ANSWER Low refrigerant charge sure and high normal sub-cooling. the A solenoid valve is used to allow a reciprocating refrigeration machine to adapt to the load on ANSWER-An electrical current the system. the opening of the solenoid valve is caused by: creating a magnetic field The process by which refrigerant is extracted and cleaned for reuse without requirements for reclamation is called- ANSWER-Rceycle 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: - ANSWER1.39 You are the engineer running a 2000-ton (steam-driven turbine} centrifugal refrigeration system, arcfrigeration syslom supplics 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? - ANSWERCheck the condenser water pump and restart the refrigeration system Electrical current is measured in?- ANSWER-Amperage How would you put an additional pump online? - ANSWER-Open suction valve, open discharge valve gradually Of the following, the major advantage of a shell and coil condenser is: - ANSWER-There is less dangers of devcloping leaks An engineer needs Lo vary the flow of refrigerant in a refrigeration syslem. which operation in the flow of the system does not include: - ANSWER Solenoid va. 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: - ANSWER-Flood the evaporator What are steam elector used for on the surface condenser of a system with a turbine: - ANSWER. To create a proper opening exhaust system Water and moisture is serious problem ina refrigerant system how to avoid: - ANSWER-Proper cvacualion al the charging of the system The most important requirements for a good evaporator is that: - ANSWEF-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: - 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 altach bulb at the: - ANSWER-The outlet ond of the coil To convert walor 32F to ice al the samo lempcralure a refrigeration system must remove: - ANSWER-The latent heat of fusion The use of oil in the refrigeration machine is to: - ANSWER-Reduce wear and friction in the compressor parts significantly lower than normal. which of the following action would you avoid taking: - 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. - ANSWER40 psi Which of the following will connect to the middle port ona gauge manifold? - ANSWER-Vacuum pump The most important reason for installing a muffler in a reciprocating refrigerant machine is: - ANSWER-To contain the compressor pulsation noise Of the following, the statement that most accurately characterize a hermetic compressor is that it: - ANSWER-Will have both the compre: or and motor enclosed is gas Light housing Tn the picture the valve is in what position (45 degree angle to the lefy- 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?- ANSWER King valve, filter drier, solenoid valve, sight glass Ahigh-side float valve is used to maintain: - ANSWEF-Constant level of refrigerant in the evaporator Picture of pump: - ANSWERNin discharge, check valve y degree reducing elbow, pump suction, pump casing, pump Picture of compressor: - ANSWER-Oil charging port allows for the addition and removal of oil from the compressor A facility has failed to maintain water treatement to a refrigerant system: - ANSWER-Increase in the condenser pressure Which of these compressors is not a positive displacement type compressor? - ANSWER. Centrifugal Where is emergency power not required according to code? - ANSWER Data centers What is the most widely used regulation book by operating engineers is?- ANSWER-EPA What type of refrigerant do you need FDNY approval for? - ANSWER-Propane Centrifugal pressure is determined by? - ANSWER-Speed of motor Asingle phase 208 VAC circuit has 2 hot wires and the third is? - ANSWER-Ground Liquid refrigerant that has passed through a meter device is a ?- ANSWER-Low pressure saturated liquid With a 75 degree dry bulb and a 73 degree wet bulb the relative humidity is? - ANSWER-Very high A FDNY permit is required to conduct hot works for? - ANSWER-se of oxygen and flammable gas FDNY is most concerned with which ASHRAE refrigerant classification? - ANSWER-A3 How long must a fire alarm log book be kept? - ANSWERS years What is the minimum requirement an engineer needs to log readings? - ANSWEF-Once per shift You are the only engineer on duty with a machine running. a vice president tells you to shovel snow. what should you do?- ANSWER-Do not leave the building How often must you do an emergency power testing? - ANSWER Monthly What is the responsibility of a B29 COF holder? - ANSWEFR-Inspect the battery system Why is refrigerant gauge called a compound gauge? - ANSWERIt reads positive pressure and vacuum Which of the following does not require flame resistant treatment? - ANSWER-ART work ina muscum 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? - ANSWER. Temperature of chilled waler being pumped to the space being cooled Regardless of the ASHRAE refrigerant classification in use, in the event of a refrigerant escape the eer should be aware of? - ANSWER-Asphyxiation gi What type of refrigerant is found inside the machines Gauges? - ANSWER-Same type of refrigerant inside the machine Tfr of two istance is cut in half, what happens to the power factor? - ANSWEI@Increases by a factor What are pre hot works procedures performed prior to hot works? - 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? - ANSWER-Air limiting device What is a compressor salcly head? - ANSWER-A spring on the valve plale Stand pipe coruficate should be available for? - ANSWER-FDNY and building inspector When is a chemical fire extinguisher system needed? - ANSWER-Where water is not sufficient What is most accurate about fire alarm books? - ANSWER-Must be kept in the fire alarm panel What is the volume of a box 12" x12" x12" measure? - ANSWER-1 cubic foot 
