NYC - Final RMO Exam Questions and Complete Solutions.

NYC - Final RMO Exam Questions and Complete Solutions 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 a. Raising the condenser liquid level to the maximum b. lowering the chilled water set point. c. raising the condenser head pressure d. lowering the condenser pressure - Answer: Lowering the condensing pressure The heat removed from the refrigerant in a condenser is a. sensible and latent heat b. latent heat only c. radiant heat only d. sensible heat only - Answer: sensible and latent heat The refrigerant unit that you have been assigned to is being taken out of service for major repair. You have been assigned to withdraw refrigerant from storage in suitable containers. According to the NYC fire code, you must ensure that the containers a. do not weigh more than 200lbs when filled b. Are approved by the US Department of Transportation (DOT) c. are approved by the OSHA association d. do not exceed 55 gallon in capacity - Answer: Are approved by the US Department of Transportation (DOT) Which of the following best describes how the cylinder unloader work? a. Keep in the suction valve opened while the compressor is in the return stroke. b. controls the clearance volume in the compressor with a solenoid c. controls the opening of the passage into the compressor with variable vanes d. unloads the pistons to create less pressure - 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 - Answer: Cools the motor The amount of refrigerant that flows through the orifices of an economizer is determined by the - Answer: Difference between the high side and low side pressure The installation of an inline refrigerant cleaning system is advisable - Answer: To remove impurities in the system The type of refrigerant system that is least likely to leak refrigerant into the building space that are being cooled are - Answer: Indirect systems The suction pressure of a reciprocating compressor is 65 PSIG. The discharge pressure of this compressor is 120 PSIG. The atmospheric is 14.7PSI. the compression ratio for the given condition is closest to: - Answer: 1.69 (PSIG+14.7) Then divide both PSIG to get ratio A superheated vappr 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: water supply to the pump suction inlet is below the pump level. A TXV is used to maintain constant - 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? - 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. The most important reason to sub-cool the refrigerant in the condenser is to ensure that: - Answer: A pure liquid refrigerant will enter the metering device. A refrigeration engineer is logging readings from a reciprocating system. Compressor discharge temps have dropped significantly and the suction line pressure is high. Which of the following may be causing this set of conditions? - Answer: An expansion valve is open too wide. A low side float valve is used to maintain - Answer: The level of the refrigerant in the evaporator. Regarding fire safety, which ASHRAE refrigerant safety classification indicates no flammability and low toxicity? - Answer: A1 When an expansion valve is operating properly, at the end of the evaporator will contain: - Answer: Only superheated vapor What information is not contained in a Material Safety Data Sheet-MSDS? - Answer: Cost of the material In a steam turbine, what is the function of the Kingsbury Thrust bearing? - Answer: Maintain axial positioning of the rotor shaft A centrifugal water pump is considered to be fully primed when - 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 - Answer: 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? - Answer: The 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: - Answer: Where no liquid refrigerant is present. All liquid has been recovered from a system to be overhauled, the system - 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? - Answer: The vapor density is decreasing. You are an 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 that water level in all of the cooling tower cells is very low. Which of the following immediate action would you take? - Answer: Add additional make up water to cooling tower! (no water, add more water duh) A rooftop water cooling tower is connected to a water pump in the building basement with a 12 inches diameter pipe. with the pump turned off, a pressure gauge at the pumps inlet show a pressure of 140psig, the height of the water column, in feet, would be closest to? - Answer: 323 What device protects the steam turbine from excessive speed? - 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 - Answer: Temperature and pressure controls Refrigerants are characterized by their physical properties including flashpoint, refrigeration effect, and others. Of the refrigerants in commercial and industrial the highest latent heat and refrigerant effect is - Answer: Ammonia On what characteristics is ASHRAE refrigerant safety group classification system - Answer: Flammability and toxicity Of the following, an example of an in-line refrigerant cleaning system that may need to be used with a centrifugal compressor containing r123 refrigerant is - Answer: refrigerant recycling Information about the physical and chemical properties of a hazardous material can be found in - Answer: Material safety data sheets What is the function of the turbine auxiliary oil pump? - Answer: Establish oil pressure during turbine start uip The rupture disc 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 wires connected to the refrigeration system shown below? - Answer: It allows for flexibility and accounts for vibrations 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? - Answer: The chill water temperature 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? - Answer: 440 A water chilled system uses refrigerant R123. A leak in the evaporator shell may result in? - Answer: A higher than normal high side pressure. Capacitors are used on refrigeration motors. Of the following, the function of these devices is to? - Answer: Store electrical charges during starting and running the motor. Of the following, centrifugal refrigerant machine is best characterized by? - Answer: High Volume Low Pressure Machine. Which of the following ASHRAE refrigerant safety classification is the most flammable? - Answer: A3 Which of the following correctly describes the object in the picture below? - Answer: Standpipe house outlet, to put out fires in case of emergency Modern compressors usually seal the rotating shaft as it exits the compressor housing, a spring loaded seal made of - Answer: metal or carbon The British Thermal Unit (BTU) is the measurement of heat of energy. if 10 BTU are transferred to 10 LBS of water, the water temperature increase will be closes to - Answer: 1*F A reciprocating compressor cylinder has 10 inches bore and 14 inches stroke. The volume of refrigerant, in cubic inches, will be closer to - Answer: 1099 An electronically operated control requires 24V to operate. to change the available 110v to 24v - 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? - Answer: R22 Refrigerant On a steam turbine, what would cause the atmospheric valve to open? - Answer: All answers are correct 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 discharge gauge reading of the condenser water pump is fluctuating drastically, and the motor of the condenser pump#1 is running very hot. Which of the following actions would you take? - Answer: Turn on pump#2, turn off pump#1, the trouble shoot it. Never do anything else. Always keep water flowing. Electric devices may be used to provide built in defrosting of refrigeration machine evaporator units. These devices are classified as - Answer: Resistors The flash point of compressor lubricating 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 equipments function? - Answer: Remove non condensables from the condenser (purger) The viscosity of lubrication oil is described by a number. A low viscosity number describes oil that - Answer: flows easily (think car oil 5:W30..5:W40..5:W20) lower #, thinner oil The most likely reason for a refrigeration engineer to use a psychrometer is to measure - Answer: Relative humidity of the atmosphere The most important reason to use at least two compressors in a cascade system is to: - Answer: avoid 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 increases rapidly. The most probable cause of this pressure rise is? - 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? - Answer: keeps turbine blades wear to a minimum According to the attached material safety data sheet (MSDS) R134 is a - Answer: Clear, odorless liquid and vapor Under normal condition, the refrigerant enters the compressor as a? - 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 is most likely cause by ? - Answer: Sudden drop in crankcase pressure Assume that an engineer is able to observe refrigerant water and oil together. The fluids from settle in the container from top to bottom: - Answer: Oil, water, refrigerant (YELLOWWHITEBLUE) What is the function of the vacuum breaker in a steam turbine? - Answer: To achieve a faster coast down cycle An equalizer line on a TXV is used to: - Answer: compensate for the pressure drop across the evaporator coil If R134 accidentally touches a refrigerant engineers skin, what first aid should be applied from the MSDS? - Answer: Promptly flush skin with water until all chemical is removed. In a multi stage centrifugal compressor, each stage: - 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 is low, the suction line temperature is high, of the following the one that may cause this set of conditions? - Answer: Faulty compressor valves On an operating centrifugal compressor refrigeration 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 be used in connection with - Answer: refrigerant recovery a refrigeration system uses jet ejector to raise settle oil mixed with refrigerant to the oil pump. If a restriction in the refrigerant flow to the jet ejector develops - 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: - Answer: The elimination of corrosion In relation to suction pressure of a compressor, the reading on the oil pressure gauge should read in the range closer to - Answer: 15 to 30 PSI higher Non condesable gases like air, oil vapor, or nitrogen travel through a refrigerant system with the refrigerant they usually accumulate in the - Answer: condenser the advantage of forced draft cooling tower over natural draft cooling towers is - 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 - Answer: Relieved by another licensed refrigeration engineer A system controlled by a TXV shows high discharge pressure and high normal sub-cooling. The cause is most probably a? - Answer: Refrigerant overcharge Which of the following is a correct statement? - Answer: 2.5 gallons of water weighs 20.8 pounds. Liquid level gauge glasses (except the bulls eye) are generally equipped with - Answer: Automatic shut off valves only Copper and aluminum are frequently used for condenser tubes in refrigeration systems. These metals are used because of their - Answer: High heat transfer coefficiency Assume that a refrigeration engineer has a choice of four valves to select from. Which of the following is the mot effective type of valve to control pressure? - Answer: Plug valve Where must the material safety data sheet be located? - Answer: Where available to all employees The oil collected in the oil separator is generally - Answer: returned back to the compressor What is the function of a glad steam? - Answer: seal the turbine rotor carbon rings Regarding the functioning of a steam turbine, how is the water level controlled in the surface condenser hot well? - Answer: Operation of the re circulation and overboard valves The cause of a starved evaporator might be - Answer: low refrigerant charge A refrigeration engineer is running 2 centrifugal condenser water pumps in parallel. One of the pumps is at maximum pump rate. If by mistake the refrigeration engineer throttles back on the discharge valve of the other pump, the most likely effect will be? - Answer: a reduction on the total flow rate to the condenser The total amount of heat to be removed from the refrigerant in a condenser equals the heat picked up in the - Answer: evaporator plus the heat of compression The amount of electrical power used to operate a solenoid valve or a motor is measured in - Answer: volts Of the following, the most common metering device used today in reciprocating commercial refrigeration systems under three tons capacity is - Answer: TEV The purpose of wear rings in a centrifugal pump is to - Answer: prevent wearing of the pump housing and impeller You are the engineer running a 2000- ton (steam-driven turbine) centrifucal 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 the 9-cell cooling tower on the roof is at a temperature of 90F. You want to make an adjustment to bring the temp down to 85F. Which of the following immediate actions would you take? - Answer: increase the speed of the fans A water chiller is equipped with a reciprocating compressor, a thermostatic expansion valve and air cooled condenser. A restriction in the refrigerant liquid line would result in? - 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 - Answer: An electrical current creating a magnetic field. The process of which refrigerant is extracted and cleaned for reuse without requirements for reclamation is called - Answer: recycle A centrifugal compressor is in operation with suction pressure in 3psig and the discharge is 10psig, with an atmospheric pressure of 14.7, which is the ratio closest to? - Answer: 1.39