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Refrigeration System Test and Answers, Exams of Electrical and Electronics Engineering

A refrigeration system test with a list of questions and correct answers. It covers various topics related to refrigeration systems, including the use of jet ejectors, pressure control valves, centrifugal pumps, water cooling towers, refrigerant properties, compressor characteristics, and refrigerant flow components. Detailed information and explanations for each question, making it a valuable resource for students or professionals working in the field of refrigeration and hvac systems. The comprehensive nature of the content and the focus on practical applications suggest that this document could be useful for study notes, lecture notes, or as a reference material for exams, assignments, or university essays related to refrigeration engineering.

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2024/2025

Available from 09/20/2024

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Download Refrigeration System Test and Answers and more Exams Electrical and Electronics Engineering in PDF only on Docsity! Z51 REFRIGERATION TEST LATEST TEST | ALL QUESTIONS AND CORRECT ANSWERS | LATEST VERSION | GRADED A+ | VERIFIED ANSWERS 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: ------CORRECT ANSWER---------------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: ------CORRECT ANSWER---------------The elimination of corrosion In relation to the suction pressure of a compressor, the reading on the oil pressure guage should read in the range, closer to: ------CORRECT ANSWER---------------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: ------ CORRECT ANSWER---------------Condenser The advantage of forced draft cooling tower over natural draft cooling towers is: ------CORRECT ANSWER---------------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: ------ CORRECT ANSWER---------------Relieved by another licensed refrigeration engineer A system controlled by a TXV shows high discharge pressure and high normal subcooling. The cause is most probably a: ------CORRECT ANSWER---------------Refrigerant overcharge Which of the following is a correct statement? ------CORRECT ANSWER---- -----------2.5 gallons of water weighs 20.8 pounds Liquid level gauge glasses (except the bull's eye) are generally equipped with: ------CORRECT ANSWER---------------Automatic shut off valves only Copper and aluminum are frequently used for condenser tubes in refrigeration system. These metals are used because of their: ------ CORRECT ANSWER---------------High heat transfer coefficient Assume that a refrigeration engineer has a choice of four valves to select from. Which of the following is the most effective type of valve to control pressure? ------CORRECT ANSWER---------------Plug valve Where must the Material Safety Data Sheets be located? ------CORRECT ANSWER---------------Where available to all employees A centrifugal compressor is in operation with suction pressure is 3 PSIG and the discharge is 10 PSIG. What is the atmospheric pressure is 14.7 which is the ratio closets 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 danger 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---------------Flooding of the evaporator A chill water system uses refrigerant R-134. A leak in the evaporator shell may result in? ------CORRECT ANSWER---------------Set off the refrigerant monitor alarm What are the steam ejectors used for on the surface condenser of a system with a turbine? ------CORRECT ANSWER---------------To create a proper operating exhaust vacuum Water and moisture is a 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 notices 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 that: ------CORRECT ANSWER---------------There is not enough refrigerant in the system While doing a routine line inspection, the engineer notices the bulk of the TXV on the floor. The refrigerant engineer should attach bulb at the: ------ CORRECT ANSWER---------------The outlet end of the coil To convert water at 32 degrees F to ice at the same temperature a refrigeration system must remove: ------CORRECT ANSWER--------------- The latent heat of fusion Efficiency of the refrigerant cycle is affected by the operations 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 NYC Fire Code, you must ensure that the containers: ------CORRECT ANSWER---------------Are approved by the US Dept. of Transportation Which of the following best describes how the cylinder unloader works? ---- --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 A low side float valve is used to maintain: ------CORRECT ANSWER--------- ------The level of the refrigerant in the evaporator Regarding fire safety, which ASHRAE refrigerant safety classification indicates no flammability and lower toxicity? ------CORRECT ANSWER------ ---------A1 When an expansion valve is operating properly, at the end of the evaporator will contain: ------CORRECT ANSWER---------------Only superheated vapor What information is not contained in a Material Safety Data Sheet? ------ CORRECT ANSWER---------------Cost of the material In a steam turbine, what is the function of the Kingsbury thrust bearing? ---- --CORRECT ANSWER---------------Maintain axial positioning of the rotor shaft A centrifugal water pump is considered to the fully primed when? ------ CORRECT ANSWER---------------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? ------CORRECT ANSWER------- --------Level type tubing bender A reciprocating compressor is making a knocking sound during operation. If the refrigerant worn parts are not causing the knocking, what probably the cause? ------CORRECT ANSWER---------------Slugging of the liquid refrigerant In order for a refrigerant to become superheated, it must be heated in a section of the low side refrigerant line: ------CORRECT ANSWER-------------- -Where no liquid refrigerant is present All liquid has been recovered from a system to be overhauled, the system: - -----CORRECT ANSWER---------------Should not be opened until all vapor has been 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? ------CORRECT ANSWER---- -----------The compressor efficiency 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 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 actions would take? ------CORRECT ANSWER---------------Add additional make up water to the cooling tower A rooftop water cooling tower is connected to a water pump in the building basement with a 12 inch diameter pipe. With the pipe turned off, a pressure gauge at the pumps inlet show a pressure of 140 PSIG the height of the water column, in feet, would be closest to: ------CORRECT ANSWER-------- -------323 What device protects the steam turbine from excessive speed? ------ CORRECT ANSWER---------------Governor assembly 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 be the: ------CORRECT ANSWER---------------Temperature and pressure controls Refrigerants are characterized by their physical properties included flashpoint, refrigeration effect, and others. Of the refrigerants in commercial and industrial, the one with the highest latent heat and refrigerant effect is: - -----CORRECT ANSWER---------------Ammonia Of what characteristics is ASHRAE refrigerant safety group classification system: ------CORRECT ANSWER---------------Flammability and toxicity Of the following, an example of an in line refrigerant cleaning system that may be used with a centrifugal compressor containing R-123 refrigerant is: ------CORRECT ANSWER---------------Recycling Information about the physical and chemical properties of a hazardous material can be found in: ------CORRECT ANSWER---------------Material Safety Data Sheet An electrically operated control requires 24 volts to operate. To change the available 110 volts to 24 volts ------CORRECT ANSWER--------------- 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: ------ CORRECT ANSWER---------------R-22 On a steam turbine, what would cause the atmospheric valve to open? ----- -CORRECT ANSWER---------------All answers (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 rerigeration system, a refrigeration system supplies chilled water to a college campus with multiple buildings. Making your rounds, you notice that the condenser water pump #1 is making a lot of noise, the discharger guage reading of the condenser water pump is fluctuating drastically, and motor of the condenser pump #1 is running very hot. Which of the following would you take: ------CORRECT ANSWER---------------Turn on pump #2, shut off pump #1, and troubleshoot 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 a 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 describes the equipment's function: ------CORRECT ANSWER---------------Remove non-condensables 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 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 shuts the compressor off. When the machine is stopped, the refrigeration engineer notices that the suction pressure increases rapidly. The most probable cause of this pressure rise is: ------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 According to the attached Material Safety Data Sheet, R-134 is a: ------ CORRECT ANSWER---------------Clear, odorless liquid and vapor Under normal conditions, the refrigerant enters the compressor as a: ------ CORRECT ANSWER---------------Low pressure, super-heated 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 as follows: ------CORRECT ANSWER---------------Oil, water, refrigerant What is the function of the vacuum breaker in the steam turbine? ------ CORRECT ANSWER---------------To achieve a faster cost down cycle There is an decrease in the efficiency of a reciprocating compressor. This mostly likely caused by? ------CORRECT ANSWER---------------Leaking suction valve The suction and discharge valve of the reciprocating compressor are mounted as follows: ------CORRECT ANSWER---------------Discharge valve 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 noticed that the discharge pressure of your condenser water pump is significantly lower than the normal. Which 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 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 reciprocating refrigerant machine is? ------CORRECT ANSWER---------------To contain the compressor pulsation noise Of the following, the statement that most accurately characterizes 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 ------CORRECT ANSWER--------- ------The valve is cracked open What is the order of components on the liquid line of reciprocating system from the condenser? ------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 Picture of a pump ------CORRECT ANSWER---------------Ninety degrees reducing elbow, pump suction, pump casing, pump discharge, check valve Picture of a compressor ------CORRECT ANSWER---------------Oil charging port allows for the addition and removal of oil from the compressor A facility has failed to maintain water treatment to a refrigerant system ------ CORRECT ANSWER---------------Increase in the condenser pressure Which of these compressors is not a positive displacement type compressor? ------CORRECT ANSWER---------------Centrifugal Where is emergency power not required according to code? ------ CORRECT ANSWER---------------Data centers What is the most widely used regulation book by operating engineers? ------ CORRECT ANSWER---------------EPA (Environmental Protection Agency) What type of refrigerant do you need FDNY approval for? ------CORRECT ANSWER---------------Propane Centrifugal pressure is determined by? ------CORRECT ANSWER------------- --Speed of motor A single phase 208 VAC circuit has 2 hot wires, the third is the: ------ CORRECT ANSWER---------------Ground Liquid refrigerant that has passed through a metering device is a: ------ CORRECT ANSWER---------------Low, pressure saturated liquid With a 75 degree dry bulb and a 73 degree wet bulb, the relative humidity is: ------CORRECT ANSWER---------------Very high After recovering liquid refrigerant from a centrifugal chiller, the next step is to: ------CORRECT ANSWER---------------Recover vapor What is the responsibility of a B29 COF holder? ------CORRECT ANSWER- --------------Inspect the battery system Why is a 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---------------Artwork in a museum An engineer observes a gauge that saturation pressure of a refrigerant. If chilled water is circulated as the cooling medium this reading best be used to estimate the: ------CORRECT ANSWER---------------Temperature of chilled water being pumped to the spaces 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 machines 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 preformed prior to hot works? ------ CORRECT ANSWER---------------Check area once a day leading up to hot works A chilled water system that has an air cooled condensing unit on a roof during cold weather, has what type of protection? ------CORRECT ANSWER---------------Air limiting device What is a compressor safety head? ------CORRECT ANSWER---------------A spring on the valve plate Standpipe 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 the most accurate about fire alarm books? ------CORRECT ANSWER---------------Must be kept in the fire alarm panel What is the volume of a box 12" x 12" x 12" measure? ------CORRECT ANSWER---------------1 cubic foot A condenser pump is supplied with 85 degree water from a cooling tower, and returns to the tower at 88 degrees. The 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---------------Overcharge of refrigerant Fireproof decorations in buildings are used 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 for? ------CORRECT ANSWER-------------- -Maintaining condenser pressure to a 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--------------- Put a non-combustible barrier to protect the sprinkler head How long does it take to warm up a steam turbine? ------CORRECT ANSWER---------------10-15 minutes 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---------------8th Floor 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 has been asked to estimate the cost of operating a 5 horse power motor. Because the plant is build by energy consumed as kilowatt- hours, the technician will have to calculate the conversion. The equivalent in energy of a 5 horse power motor operating for 9 hours in kilowatt-hours is closest to: ------CORRECT ANSWER---------------33.6 A standpipe system will be out of service for two days. How long should there be a fire watch? ------CORRECT ANSWER---------------The entire time the standpipe is out of service A circuit breaker has a similar function as what: ------CORRECT ANSWER- --------------A fuse How do you start a centrifugal chiller? ------CORRECT ANSWER-------------- -Start the chilled water pump, start the condenser water pump, check oil, start cooling tower, start compressor If a sprinkler system is offline for two days, how often do you need to inspect it until it is returned back to service? ------CORRECT ANSWER------ ---------Continuously, 24 hours a day until system is restored The only refrigerant/temperature chart available to a refrigerant engineer lists the temprature in degrees Celsius. If the chart indicates a Celcius temperature of 5 degrees, the equivalent in Fahrenheit is ------CORRECT ANSWER---------------41 degrees In the picture below, what does the equipment detect? ------CORRECT ANSWER---------------Refrigerant leaks In a building with multi-zone standpipe system, how does each zone get supplied with water? ------CORRECT ANSWER---------------Each zone will have its own automatic water supply Which service valve should be installed to isolate a dual pressure relief valve while keeping system in service? ------CORRECT ANSWER------------- --Three way valve When will the BTU's exchanged be the greatest? ------CORRECT ANSWER---------------Low evaporator temperature, high condenser temperature You find that the check valve on a centrifugal pump is leaking. When would the most damage be caused to the pump? ------CORRECT ANSWER-------- -------On startup of the pump A motor winding is touching the inside of the motor housing. This could result in: ------CORRECT ANSWER---------------Shock may occur to personnel An engineer suspects a short of the motor winding have caused the motor to trip on overload. The engineer should use what instrument to check the motor: ------CORRECT ANSWER---------------Ohmmeter An engineer would expect a relief valve to start function at a pressure: ------ CORRECT ANSWER---------------Design pressure How many BTU's are removed in a 30 ton system? ------CORRECT ANSWER---------------360,000 BTU's per hour An engineer is requested to replace a gauge on the high side of the system. The pressure graduation rate should be: ------CORRECT ANSWER---------------At least 1.2 times the design pressure An automatic expansion valve maintains a constant: ------CORRECT ANSWER---------------Evaporator pressure When a thermostatic expansion valve is operating properly the end of the coil will contain? ------CORRECT ANSWER---------------Superheated vapor If the external equalizing line is disconnected from a TEV? ------CORRECT ANSWER---------------The evaporator would flood Which system is most likely to leak into the building spaces being cooled? - -----CORRECT ANSWER---------------Direct systems What device records the speed of the turbine's shaft? ------CORRECT ANSWER---------------Tachometer What controls a solenoid valve on a motor? ------CORRECT ANSWER------- --------Volts How long does it take to warm up a steam turbine prior to start-up? ------ CORRECT ANSWER---------------15 - 20 minutes What device is used to control the speed of a steam turbine? ------ CORRECT ANSWER---------------Governor valve What is the heat transfer rate of a 30 ton system? ------CORRECT ANSWER---------------360,000 BTU's per hour Refrigerant leaves the compressor as a? ------CORRECT ANSWER---------- -----Super-heated vapor Water, oil and refrigerant would settle in a container in what order from top to bottom? ------CORRECT ANSWER---------------Oil, water, refrigerant. The amount of refrigerant that passes through an orifice plates is determined by the? ------CORRECT ANSWER---------------Difference between high side and low side pressure A centrifugal water pump is considered fully primed when? ------CORRECT ANSWER---------------It is full of liquid and air is vented According to the NYC code, prior to recovering refrigerant from a unit, you must ensure that the containers used for storage? ------CORRECT ANSWER---------------Are approved by the U. S department of transportation What would be the best way to install a 90 degree turn in a hard copper piping system? ------CORRECT ANSWER---------------Use a factory made 90 degree elbow and braze What is the maximum amount of refrigerant that could be stored in a machinery room? ------CORRECT ANSWER---------------300 pounds An electrical wiring diagram shows? ------CORRECT ANSWER--------------- Each of the wire connections (terminations) required by the system What type of valve would be used to replace a pressure relief device, while keeping the system in service? ------CORRECT ANSWER---------------Three way valve A thermostatic expansion valve regulates ___? ------CORRECT ANSWER-- -------------Flow of refrigerant to the evaporator