RMO Test Exam Questions and Complete Solutions

RMO Test Exam Questions and Complete Solutions A fusible plug melts at - Answer: 280F A hermetic compressor is operating with a low refrigerant charge. What is the most likely effect this condition would have on the compressor? - Answer: compressor would operate at higher temperature A low pressure refrigeration system has a pin hole in the evaporator. What is the most likely result? - Answer: a high head pressure A reciprocating system using a evaporative condenser, the muffler is installed between the - Answer: compressor and evaporative condenser A refrigeration unit is measured in - Answer: BTUs A RMO is logging readings from a reciprocating compressor refrigerating unit. The crankcase and compressor discharge temperature have dropped significantly and suction line pressure is high. Of the following the one that may cause this set of condition is: - Answer: faulty compressor valves A RMO notices excessive cycling of the temperature control for a reciprocating compressor refrigeration unit. The crankcase temp is high, the compressor discharge temp is low and the suction line is high, of the following the one that may be causing this set of condition is: - Answer: condenser operation, dirty tubes, or cooling water control A thermal bulb is attached to the suction pipe between the evaporator coil and the compressor covered by an insulating line. Assuming the machine room is 85F, unraveling of the insulation would result in: - Answer: flooded evaporator A water regulating valve is installed in a water cooled condenser. The operating force on this valve is respondent to: - Answer: a high side pressure According to the NYC fire code classification of refrigerants, ammonia and sulphur dioxide AR grouped into: - Answer: Group 2 An electric motor that is rated at 3 HP will? - Answer: use three phase An oil with low viscosity would: - Answer: not be used for refrigeration An operator confirms that a chiller water pump in a refrigerating system employing R-123 is captivating, of the following, the most likely cause for this condition is - Answer: malfunction of the water make up float valve An operator notice that a centrifugal pump operates satisfactorily when delivering at full discharge, but loses water flow if throttled. The operator would most accurately assume that this condition is due to: - Answer: clogged strainer in pump inlet An operator observes a reading of 60 degrees Celsius on a refrigerating unit. The same reading in Fahrenheit scale would be closer to - Answer: 140 An operator reads the valve tag on a pressure relief valve and notices that the valve is set to unseat at an evaporating pressure of 15 PSI, the corresponding set pressure in inches HG is - Answer: 30.3 An operator suspects that a vertical check valve on a discharge of a centrifugal pump is defective. This is a condenser pump and one of the three pumps is parallel. If the suspicion is true and the check valve fails to seat when required. The pump and connecting piping will most like be damaged when: - Answer: starting up an additional pump An operator suspects that shorted motor windings have caused the motor overloads to trip. In order to investigate this condition, the operator would be most correct to use - Answer: ohmmeter An operator verifies that a condenser water pump is caveating in a refrigeration system employing R-22 refrigerant. The most likely cause for this condition is: - Answer: Faulty cooling tower water level controller Assume that a new valve plate has been installed while they are repairing a reciprocating compressor in a refrigerating plant. The installation of a new valve plate will require the replacement of - Answer: all valve and valve seats Assuming that a refrigeration plant uses a horizontal shell and tube condenser with the water in the tubes and refrigerant in the shell. In controlling the operation of the condenser, the operator should take into account that most likely the heat transfer rate BTU/PER SQ FT PER SECOND in the condenser will: - Answer: increase with the velocity of the water in the tubes Because of the latent heat load, refrigeration machine operator was instructed to start the reciprocating plant for air-conditioning. The first thing to do is: - Answer: Turn on chilled water pump, condenser water pumps, and cooling tower fans Bubbles in the sight glass are most likely cause by: - Answer: Partially plugged filter/drier Clearance volume - Answer: affects compressor capacity compound gauges can measure - Answer: above atmospheric, below atmospheric, temperature concerning leakage - Answer: gate valves causes more leakage copper used in refrigeration systems, like in heat exchangers, because - Answer: high thermal conductivity During a hot weekend, an RMO is instructed to start an additional reciprocating machine. The sequence of actions on start up would most likely be - Answer: start chiller and condenser water pumps, start cooling tower fans, check compressor oil levels, check that valves are in correct position, turn machine on electric devices may be used to provide built in defrosting of refrigerating machine evaporator units. These are classified as - Answer: resistors Flood evaporators have high heat transfer per square foot, what may be a disadvantage - Answer: requires a high charge how low can chiller water temperature be - Answer: 33F How many BTUs would be removed in a 30 tone system - Answer: 360,000 per hour IF A LOW SIDE FLOAT IS BEING USED: - Answer: it will control refrigerant flow If had to install a solenoid valve to a system which uses 110 volts and needed to convert it to 24 volts, what would you use - Answer: step down transformer If the low pressure cutout cycles the compressor off, what starts the compressor again - Answer: low pressure cut out IF UNLOADERS WERE TO FAIL IN THE UNLOADED POSITION, WHAT HAPPENS IN A SYSTEM USING RECIPROCATING COMPRESSOR? - Answer: The evaporating will starve cause high superheat not enough refrigerant to coil If you had 38F in the evaporator, what should your suction pressure be for R-22 - Answer: 66 PSIG If you have 62 PSI at 35F and 70 PSI at 45F, what would be 38F be? - Answer: 64.4 If you were running three compressors, which best describes the state of refrigerant leaving the third evaporator coil - Answer: superheated vapor In a three stage centrifugal chiller, what happens to the pressure as it reached the final stage - Answer: increases In a centrifugal three stage compressor - Answer: pressure increases with each stage impellers are same size In addition to regulating the refrigerant flow according to the needs of the system, metering devices also serve to - Answer: restrict flow of refrigerant from the high side to low side In relation to suction pressure of a compressor, the reading in the oil pressure gauge should read - Answer: 15-30 PSI higher Latent heat and refrigeration effect are usually listed as refrigeration properties. The refrigerating effect is also always a lower value than the latent heat because the - Answer: Heat required to cool the refrigerant from compressor discharge to evaporative temperature is subtracted from latent heat. The one that best describes refrigerant 22 is - Answer: odorless when mixed with air One of the primary reasons for the insulation of a crankcase breather line is - Answer: to prevent oil slugging in the compressor Oil flashpoint temperature in the compressor should be - Answer: higher than the heat of compression Regardless of safety classification of the refrigerant in use, in the event of refrigerant escape, the RMO should be aware of - Answer: oxygen deprivation Removing the insulation on the suction line, with the engine temperature at 85F, what will occur - Answer: excessive superheat Shell and coil condensers have the advantage of - Answer: has less chance of developing leaks Shell and tube condensers have the advantage of - Answer: removing heads for cleaning the water sides of the tubes the refrigerant connections does not have to be disrupted Superheated vapor flowing into a reciprocating compressor protects the compressor parts against liquid intake. One of the problems associated with superheat is that - Answer: It will decrease the capacity of the compressor and the refrigeration machine The accessories on the liquid lie are in what order - Answer: receiver, drier, solenoid valve, and sight glass The advantage of forced draft over natural draft cooling tower - Answer: The possibility of lower water out temp There is no dependence on natural wind velocity Use of a smaller tower size The condenser that uses air and water for cooling is the - Answer: evaporative The cylinder unloader controls capacity, is there any other function it may have - Answer: assist with compressor start up The dividing line between the high and low sides of the refrigeration system is - Answer: compressor outlet and the orifice of the metering device An example of an "inline" refrigerant cleaning system which may be used with a centrifugal compressor containing R-123 refrigerant is - Answer: refrigerant recycling Most accurate statement regarding compressor motors that run in refrigerant atmosphere is that they - Answer: use materials tailors to the refrigerant The heat that boils off in a condenser is - Answer: latent heat The mechanism sitting above the evaporator is known as - Answer: purge unit The metering device used in a condenser is a high side float, this device will - Answer: control the amount of refrigerant in condenser The most important reason to use two compressors in a cascade system is to - Answer: accomplish lower temperature The ratio of actual pressure of water vapor in the atmosphere to the saturation pressure/temperature is called - Answer: relative humidity The refrigeration unit which you have been assigned to is being taken out of service for major repairs. You have been assigned to withdraw refrigerant for storage in suitable containers. According to the NYC Fire Law Handbook you must ensure that containers - Answer: are approved by the U.S. Dept. of Transportation The rupture disk is always piped into the - Answer: low side The suction and discharge valve in a reciprocating compressor are positioned - Answer: Both over and under valve plate There is an automatic water regulating valve on a reciprocating chiller. Water is entering the condenser at 88F. You know there is no scale and the tubes are not covered with film. What can be caused this condition? - Answer: Water valve stuck open What does centrifugal compressor generate inside? - Answer: high volume, low pressure What is 29.92" HG in KPA - Answer: 101.3 What is a method used to calibrate a thermometer? - Answer: Place thermometer in cup of ice What is the cubic feet if a 20FT long 6Ft vessel on the evaporator? - Answer: 565 Cubic Feet What is the maximum percentage that a refrigerant can be stored in a cylinder? - Answer: 75% What is the state of refrigerant as it leaves the compressor and as it leaves the condenser: - Answer: superheated vapor and warm sub-cooled liquid What refrigerants are you not able to dump? - Answer: CFC, HCFC, HFC, any refrigerant containing chlorine or fluorine What shaft seal prevents vapor from leaking out of compressor - Answer: stuffing box When a compressor is running fine at full flow and you throttle down flow causing the compressor to stop running normal (short cycle), why would this happen? - Answer: low pressure cut out When a compressor is said to have a safety head this means - Answer: compressor has pressure relief valve When a system does not have unloaders, what is needed? - Answer: other capacity control When an evaporator is not equipped with an equalizer line, you would most likely find: - Answer: a distributor When charging a centrifugal system the position of the valve is: - Answer: back seated When dry bulb is 75F and wet bulb is 75F - Answer: 100% relative humidity When operating a reciprocating refrigeration system with a belt driven compressor, an RMO notices that one of the four belts is broken. The most advisable course of action for the RMO would be to - Answer: replace all four belts with a new set When recovering R-22, what color would the cylinder be that you are storing the refrigerant in - Answer: yellow tops When the temperature and the load increase and you need to add another pump online, you would - Answer: open suction and throttle discharge When there is a 5lb pressure drop across evaporator, you need an external equalizer line, what happen if it disconnects - Answer: evaporator would starve When will the BTUs absorbed by the condensing water be the greatest - Answer: high condenser temperature, low condenser water temperature When you plan on overhauling a system and you have recovered all liquid refrigerant, what is next? - Answer: recover all vapor, then do work While doing a routine inspection, the RMO noticed the bulb of the TEV on the floor, the operator should attach the bulb at: - Answer: end of coil While operating an R-12 reciprocating system, the RMO noticed the oil foaming in the crankcase, this condition most likely would have been caused by: - Answer: sudden drop in crankcase pressure While using a halide torch to check for refrigerant leaks, if the flame was to turn yellow, what happened? - Answer: Restriction in tube With an induced draft cooling tower, what is the lowest temperature attainable for a cooling tower? - Answer: dry bulb higher than wet bulb