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RMO Written Exam Questions and Answers 2024
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RMO Written Exam Questions and Answers 2024
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RMO Written Exam Questions and Answers 2024 1. How do automatic expansion valves work?: Evaporator pressure closes the valve and spring pressure opens the valve. 2. When will a faulty check valve cause the most damage?: On startup. 3. What will happen if a TEV'S sensing bulb insulation wears off of the suction line in an 85 F Degree room?: You will flood the evaporator. 4. What can a clogged pump strainer cause?: A reduction or loss in water flow which will lead to high condenser head pressure. 5. What part of the Refrigeration system is the solenoid valve part of?: The pump down cycle (Thermostat - Solenoid Valve - Low Pressure Controller). 6. What is the proper machine start up procedure?: Check oil, start chilled water pump, start condenser water pump, start tower fans and start up machine. 7. How does a reciprocating machine cycle compressors on and off?: Through the use of the low pressure control. 8. What refrigerant has the best Refrigeration effect and highest latent heat? - : Ammonia (R -717) / ASHRE Classification is B2. 9. What is the leaving water temperature of an induced draft cooling tower that is operating efficiently?: At some temperature between the dry and wet bulb temperature. 10. What could a sudden reduction in the supply flow of the cooling tower water result in?: An increase in head pressure. 11. How do reciprocating compressor unloaders operate?: By keeping the com- pressor suction valves open. 12. Which side of the compressor is R-22 vapor charged into?: The suction side. 13. What should the percentage of lubricant circulated through a well de- signed system be?: Lubricant should not exceed 10%. 14. What is oil foaming in the compressor a result of?: Liquid refrigerant in the crankcase. 15. What is the main reason for installing an oil separator on the discharge line?: To return oil back to the compressor crank case. 16. What causes the foaming of oil in a reciprocating compressor using the splash system for lubrication?: A rapid decrease in pressure. 17. What is the purpose of oil in a refrigerant compressor?: It reduces ware and friction. 18. What is a filter dryer used to remove?: Moisture, particles and contaminants. 19. Where in a refrigeration system is the oil separator located?: On the dis- charge line as far from the compressor as possible. 20. If a motor has 4 belts and 1 of the 4 belts are worn, how many belts should be replaced?: All of the belts should be replaced. 21. Does a solenoid valve vary or control the flow of refrigerant?: No. 22. What accessory meters and controls the flow of refrigerant into the evap - orator?: The TEV (Metering Device). 23. What will occur if you use an automatic expansion valve with a variable load?: You will starve the evaporator. 24. What does an automatic expansion valve do?: It maintains a constant evap - orator pressure. 25. What could cause the evaporator to not respond to the adjustments of the TEV?: Oil logged on the low side. 26. What can non-condensible's cause?: High head pressure. 27. When will compressor motor horsepower increase?: It will increase as the head pressure increases. 28. When will compressor motor horsepower decrease?: As the suction pres- sure increases. 29. When using a brine solution in a system what can be used to prevent rusting?: Di-Chromate Tablets. 30. What would cause a Halide torch flame to turn yellow?: A clogged sample tube. 31. What is the purpose of having 2 compressors in a cascade system?: To operate and very low temperatures and avoid high compression ratio. 32. Why is a pressure relief valve better than a fusible plug?: Because it can be re-seated and is cost efficient. 33. What could cause compressor knocking?: Liquid refrigerant slugging the compressor. 34. What would occur if a TEV'S spring were to break?: It would flood the evaporator and raise the suction pressure because a TEV uses spring pressure as its closing force. Thus, if the spring does not close the TEV refrigerant will constantly be metered into the evaporator. 35. What is the purpose of the TEV equalizer line?: It compensates for the pressure drop in the evaporator. Simply put, it equalizes pressure drop lost across the evaporator. 36. What should be done when installing copper pipe and a 90 degree elbow is needed?: You should BRAZE in a FACTORY MADE 90 degree elbow. 37. What is the purpose of a service valve stem cap?: It protects the valve from refrigerant leakage. 38. What advantage do semi hermetic compressor's have over hermetic com- pressor's?: Semi hermetic compressor's can be serviced. 39. What happens when using portable compressor recovery unit to remove vapor?: The vapor density is decreased. 40. What is the purpose of an unloader?: To decrease capacity (capacity control). 41. What determines the amount of pressure that flows through the orifice plates?: The difference in pressure between the high side and the low side of the system. 42. How can you check proper operation of a thermometer?: Local 94 answer - Place it in a container with ice water. Turner answer - Place it on an open container of boiling water. 43. How many phases will a 3 HP motor use?: 3 Phases. 44. If you were running 3 compressors what would the state of the refrigerant be leaving the 3rd evaporator coil?: It would be a slightly superheated vapor. 45. What does a TEV do?: It restricts the amount of refrigerant that flows from the high side to the low side. 46. When does a halide torch turn from blue to green or purple?: When a leak is detected. 47. What does a rectifier do?: It converts AC voltage to DC voltage. 48. What is the function of a thermostat?: It's purpose is to cycle the compressor on and off. 49. What is the main purpose for a crankcase breather line?: The main purpose is to prevent oil from slugging the compressor. 50. Where can the middle port on manifold gauges be connected to?: It can be connected to the recovery machine, charging cylinder or vacuum pump. 51. Why is a forced draft cooling tower better than a natural draft cooling tower?: Because it is smaller and it is not affected by prevailing winds. 52. What should an RMO do after recovering as a liquid when attempting to open the chiller for servicing?: You should next, recover as a vapor and then proceed to open the chiller for servicing. 53. What is the proper way to start up a pump?: Open the suction valve and then slowly throttle open the discharge. 54. What form of energy do Solenoid valves create?: A magnetic field of energy. 55. What pressure is R -22 at 38 degrees on a PT chart?: 65.6 PSI. 56. What does the chillers purge unit do?: It removes air and non-condensible's from the condenser. 57. What can overcharge of refrigerant cause?: High discharge pressure. 58. A sling psychrometer has both wet and dry bulb temperatures, if both temperatures are the same what would this indicate?: 100% relative humidity. 59. What is the purpose of the swirler at the top of a water box in a vertical shell and tube condenser?: It's purpose is to force water down the tubes and allow the water to come in contact with as much of the interior wall of the tubes to provide greater heat transfer.The benefits of buying summaries with Stuvia:
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