MECHANIC REFRIGERATION AND AIR CONDITIONING
MECHANIC REFRIGERATION AND AIR CONDITIONING MCQs
1. The compressor motor in a hermetically sealed compressor is cooled by :
(A) Water (B) Air (C) Refrigerant (D) Nitrogen
Ans: C
2. Float valves are used in :
(A) Refrigerators (B) Large refrigeration systems
(C) Package units (D) Split AC
Ans: B
3. Velocity pressure is :
(A) Difference between Static pressure and Air pressure
(B) Difference between Total pressure and Static pressure
(C) Difference between Air velocity and Air pressure
(D) None of these
Ans: B
4. The unit of Resistance is __________.
(A) Ohm (B) Farad (C) Volt (D) Ampere
Ans: A
5. The heart of the refrigeration system is __________.
(A) Condenser (B) Evaporator (C) Liquid receiver (D) Compressor
Ans: D
6. Which line in Psychrometric chart as obliquely inclined straight lines and uniformly spaced ?
(A) Relative humidity lines (B) Specific humidity lines
(C) Enthalpy (D) Specific volume
Ans: D
7. In star delta starter the main contactor is named as :
(A) KM 1 (B) KM 2 (C) KM 3 (D) K1T
Ans: C
8. What is the purpose of adding dye in compressor lubricating oil to the Car AC system ?
(A) Identify the gas leak (B) Lubricate the engine
(C) Adding performance (D) Improve efficiency
Ans: A
9. The relationship between rotor speed ‘N’, frequency ‘f’ and no. of poles ‘P’ given by the relation :
(A) N=120f/P (B) PN=120f (C) f=120N/P (D) N=120P/f
Ans: A
10. The coil has to be rinsed after de-scaling till the pH level comes to :
(A) 5 to 5.5 (B) 6 to 6.5 (C) 7 to 7.5 (D) 8 to 8.5
Ans: C
11. The voltmeter can be used in __________.
(A) Series connection
(B) Parallel connection
(C) Combination of both series and parallel
(D) None of these
Ans: B
12. During sensible heating of moist air, specific humidity :
(A) Increases (B) Decreases
(C) Remains constant (D) None of these
Ans: C
13. The fresh air or ventilation air is a must in any comfort air conditioning system. Its purposes are __________.
(A) to provide oxygen (B) to remove carbon dioxide
(C) to remove odours (D) All of these
Ans: D
14. Refrigerant propane has the designation __________.
(A) R 11 (B) R 134a (C) R 290 (D) R 12
Ans: C
15. The expansion device used in central AC plant is :
(A) AXV (B) TXV (C) Capillary tube (D) Solenoid valve
Ans: B
16. The chemical name of refrigerant R 134a is __________.
(A) Propane (B) Dichloro diflouro methane
(C) Tetrafluoroethane (D) Monochlorodifluoroethane
Ans: C
17. Bourden tube is a __________.
(A) Pressure measuring device (B) Volume measuring device
(C) Density measuring device (D) Temperature measuring device
Ans: A
18. Three TR is equivalent to __________ of cooling effect.
(A) 5 kJ/s (B) 10.5 kW (C) 10 kJ/s (D) 7 Kw
Ans: B
19. Dry Bulb Temperature (DBT) is the actual temperature of __________.
(A) Dry air (B) Dry ice (C) Water vapour (D) Moist air
Ans: D
20. Tools used for making external threads is :
(A) Taps (B) Die (C) Thread gauge (D) Drill
Ans: B
(A) Water (B) Air (C) Refrigerant (D) Nitrogen
Ans: C
2. Float valves are used in :
(A) Refrigerators (B) Large refrigeration systems
(C) Package units (D) Split AC
Ans: B
3. Velocity pressure is :
(A) Difference between Static pressure and Air pressure
(B) Difference between Total pressure and Static pressure
(C) Difference between Air velocity and Air pressure
(D) None of these
Ans: B
4. The unit of Resistance is __________.
(A) Ohm (B) Farad (C) Volt (D) Ampere
Ans: A
5. The heart of the refrigeration system is __________.
(A) Condenser (B) Evaporator (C) Liquid receiver (D) Compressor
Ans: D
6. Which line in Psychrometric chart as obliquely inclined straight lines and uniformly spaced ?
(A) Relative humidity lines (B) Specific humidity lines
(C) Enthalpy (D) Specific volume
Ans: D
7. In star delta starter the main contactor is named as :
(A) KM 1 (B) KM 2 (C) KM 3 (D) K1T
Ans: C
8. What is the purpose of adding dye in compressor lubricating oil to the Car AC system ?
(A) Identify the gas leak (B) Lubricate the engine
(C) Adding performance (D) Improve efficiency
Ans: A
9. The relationship between rotor speed ‘N’, frequency ‘f’ and no. of poles ‘P’ given by the relation :
(A) N=120f/P (B) PN=120f (C) f=120N/P (D) N=120P/f
Ans: A
10. The coil has to be rinsed after de-scaling till the pH level comes to :
(A) 5 to 5.5 (B) 6 to 6.5 (C) 7 to 7.5 (D) 8 to 8.5
Ans: C
11. The voltmeter can be used in __________.
(A) Series connection
(B) Parallel connection
(C) Combination of both series and parallel
(D) None of these
Ans: B
12. During sensible heating of moist air, specific humidity :
(A) Increases (B) Decreases
(C) Remains constant (D) None of these
Ans: C
13. The fresh air or ventilation air is a must in any comfort air conditioning system. Its purposes are __________.
(A) to provide oxygen (B) to remove carbon dioxide
(C) to remove odours (D) All of these
Ans: D
14. Refrigerant propane has the designation __________.
(A) R 11 (B) R 134a (C) R 290 (D) R 12
Ans: C
15. The expansion device used in central AC plant is :
(A) AXV (B) TXV (C) Capillary tube (D) Solenoid valve
Ans: B
16. The chemical name of refrigerant R 134a is __________.
(A) Propane (B) Dichloro diflouro methane
(C) Tetrafluoroethane (D) Monochlorodifluoroethane
Ans: C
17. Bourden tube is a __________.
(A) Pressure measuring device (B) Volume measuring device
(C) Density measuring device (D) Temperature measuring device
Ans: A
18. Three TR is equivalent to __________ of cooling effect.
(A) 5 kJ/s (B) 10.5 kW (C) 10 kJ/s (D) 7 Kw
Ans: B
19. Dry Bulb Temperature (DBT) is the actual temperature of __________.
(A) Dry air (B) Dry ice (C) Water vapour (D) Moist air
Ans: D
20. Tools used for making external threads is :
(A) Taps (B) Die (C) Thread gauge (D) Drill
Ans: B
21. In a refrigeration cycle, pressure is maximum __________.
(A) After Expansion Valve (B) After Condenser
(C) After Evaporator (D) After Compressor
Ans: D
22. The Dalton’s law deals with the __________.
(A) Sum partial volumes of gases (B) Sum partial temperature of gases
(C) Sum partial pressure of gases (D) None of these
Ans: C
23. An automatic expansion valve is based on the principle of __________.
(A) Maintaining a constant degree of superheat
(B) Maintaining a constant pressure in evaporator
(C) Maintaining a constant temperature in the evaporator
(D) Both (A) and (B)
Ans: B
24. Window AC for cooling mode can be easily converted to heating mode by installing a :
(A) TXV (B) RCV
(C) AXV (D) Solenoid valve
Ans: B
25. Approach of a cooling tower is defined as the :
(A) Difference of DBT of surrounding air and temperature of water leaving the CT
(B) Difference of temperature of water leaving the CT and temperature of entering water
(C) Difference of temperature of water leaving the CT and WBT of surrounding air
(D) None of the above
Ans: C
26. Temporary hardness of water can be removed by :
(A) filtering (B) chemical treatment
(C) boiling (D) cooling
Ans: C
27. The cleaning efficiency of a fine filter is :
(A) 99.9% (B) 100% (C) 80% (D) 70%
Ans: A
28. Which type of fan is used in electrical motors for internal cooling ?
(A) Backward inclined fan (B) Backward curved fan
(C) Forward curved fan (D) Radial blade fan
Ans: D
29. Which senses the suction temperature in thermal electric expansion valve ?
(A) Transformer (B) Thermal bulb (C) Thermostat (D) Thermistor
Ans: D
30. Which run capacitor is used with 1.5 TR AC ?
(A) 36 mfd, 220/250 V (B) 80 mfd 220/250 V
(C) 36 mfd, 440/370 V (D) 80 mfd 440/370 V
Ans: C
31. The difference between the synchronous speed and the actual rotor speed is called :
(A) Motor speed (B) Slip speed (C) Actual speed (D) Field speed
Ans: B
32. The difference between the dry bulb temperature and wet bulb temperature is called :
(A) Dew point depression (B) Wet bulb depression
(C) Dry bulb depression (D) Humidity
Ans: B
33. A low side float valve maintains the level of refrigerant in :
(A) Condenser (B) Evaporator
(C) Baudelot cooler (D) Flooded evaporator
Ans: D
34. Boiling point of R 600a is :
(A) −33 deg C (B) −12 deg C (C) −77 deg C (D) −40 deg C
Ans: B
35. RF remote control with a range of roughly :
(A) 100 feet (B) 40 feet (C) 20 feet (D) 10 feet
Ans: A
36. Bush bearings are usually made of :
(A) Nickel (B) Bronze (C) Steel (D) Platinum
Ans: B
37. The sediments which form as a coating on cooling coil will reduce the __________.
(A) Temperature (B) Heat transfer efficiency
(C) Suction pressure (D) Heat load on evaporator
Ans: B
38. The ratio of the sensible heat to the total heat is known as :
(A) Sensible heat factor (B) ADP
(C) Enthalpy (D) Relative humidity
Ans: A
39. Cutting of sheet metal by two parallel cutting edge moving in opposite direction is termed as :
(A) Drawing (B) Swaging (C) Shearing (D) Piercing
(B) Ans: C
40. De-superheating takes place in __________.
(A) Compressor (B) Discharge line (C) Condenser (D) Both (B) and (C)
Ans: D
41. The upcoming alternative refrigerant to be used in car air conditioning system is __________.
(A) R 134a (B) R 1234ze (C) R 1234yf (D) R 764
Ans: C
42. ODP Value of HFC 134a :
(A) 1 (B) 3 (C) 0 (D) 2
Ans: C
43. In saturated air :
(A) DBT = WBT (B) WBT = DPT (C) DBT = DPT (D) All of these
Ans: D
44. VRF stands for :
(A) Varying Recirculated Flow (B) Variable Refrigerant Flow
(C) Varying Refrigerant Functions (D) None of these
Ans: B
45. The gap between the false ceiling and the main ceiling is referred as :
(A) Supply air duct (B) Plenum
(C) Return air duct (D) Diffuser
Ans: B
46. During installation of split AC unit, what is the maximum vertical distance between indoor and outdoor units ?
(A) 20 feet (B) 30 feet (C) 15 feet (D) 40 feet
Ans: A
47. Water pressure cut out switch is installed in :
(A) Cooling tower line (B) Condenser water line
(C) Chilled water line (D) Both (B) and (C)
Ans: D
48. For leak testing, maximum test pressure for split AC system is :
(A) 70 PSIG (B) 150 PSIG (C) 100 PSIG (D) 200 PSIG
Ans: B
49. Cylindrical and needle roller bearings are commonly found in :
(A) Fans (B) Roller blades (C) Gear boxes (D) DC machines
Ans: C
50. Following are the methods of food preservation :
(A) Dehydration (B) Hydration (C) Canning (D) Both (A) and (C)
Ans: D
(A) After Expansion Valve (B) After Condenser
(C) After Evaporator (D) After Compressor
Ans: D
22. The Dalton’s law deals with the __________.
(A) Sum partial volumes of gases (B) Sum partial temperature of gases
(C) Sum partial pressure of gases (D) None of these
Ans: C
23. An automatic expansion valve is based on the principle of __________.
(A) Maintaining a constant degree of superheat
(B) Maintaining a constant pressure in evaporator
(C) Maintaining a constant temperature in the evaporator
(D) Both (A) and (B)
Ans: B
24. Window AC for cooling mode can be easily converted to heating mode by installing a :
(A) TXV (B) RCV
(C) AXV (D) Solenoid valve
Ans: B
25. Approach of a cooling tower is defined as the :
(A) Difference of DBT of surrounding air and temperature of water leaving the CT
(B) Difference of temperature of water leaving the CT and temperature of entering water
(C) Difference of temperature of water leaving the CT and WBT of surrounding air
(D) None of the above
Ans: C
26. Temporary hardness of water can be removed by :
(A) filtering (B) chemical treatment
(C) boiling (D) cooling
Ans: C
27. The cleaning efficiency of a fine filter is :
(A) 99.9% (B) 100% (C) 80% (D) 70%
Ans: A
28. Which type of fan is used in electrical motors for internal cooling ?
(A) Backward inclined fan (B) Backward curved fan
(C) Forward curved fan (D) Radial blade fan
Ans: D
29. Which senses the suction temperature in thermal electric expansion valve ?
(A) Transformer (B) Thermal bulb (C) Thermostat (D) Thermistor
Ans: D
30. Which run capacitor is used with 1.5 TR AC ?
(A) 36 mfd, 220/250 V (B) 80 mfd 220/250 V
(C) 36 mfd, 440/370 V (D) 80 mfd 440/370 V
Ans: C
31. The difference between the synchronous speed and the actual rotor speed is called :
(A) Motor speed (B) Slip speed (C) Actual speed (D) Field speed
Ans: B
32. The difference between the dry bulb temperature and wet bulb temperature is called :
(A) Dew point depression (B) Wet bulb depression
(C) Dry bulb depression (D) Humidity
Ans: B
33. A low side float valve maintains the level of refrigerant in :
(A) Condenser (B) Evaporator
(C) Baudelot cooler (D) Flooded evaporator
Ans: D
34. Boiling point of R 600a is :
(A) −33 deg C (B) −12 deg C (C) −77 deg C (D) −40 deg C
Ans: B
35. RF remote control with a range of roughly :
(A) 100 feet (B) 40 feet (C) 20 feet (D) 10 feet
Ans: A
36. Bush bearings are usually made of :
(A) Nickel (B) Bronze (C) Steel (D) Platinum
Ans: B
37. The sediments which form as a coating on cooling coil will reduce the __________.
(A) Temperature (B) Heat transfer efficiency
(C) Suction pressure (D) Heat load on evaporator
Ans: B
38. The ratio of the sensible heat to the total heat is known as :
(A) Sensible heat factor (B) ADP
(C) Enthalpy (D) Relative humidity
Ans: A
39. Cutting of sheet metal by two parallel cutting edge moving in opposite direction is termed as :
(A) Drawing (B) Swaging (C) Shearing (D) Piercing
(B) Ans: C
40. De-superheating takes place in __________.
(A) Compressor (B) Discharge line (C) Condenser (D) Both (B) and (C)
Ans: D
41. The upcoming alternative refrigerant to be used in car air conditioning system is __________.
(A) R 134a (B) R 1234ze (C) R 1234yf (D) R 764
Ans: C
42. ODP Value of HFC 134a :
(A) 1 (B) 3 (C) 0 (D) 2
Ans: C
43. In saturated air :
(A) DBT = WBT (B) WBT = DPT (C) DBT = DPT (D) All of these
Ans: D
44. VRF stands for :
(A) Varying Recirculated Flow (B) Variable Refrigerant Flow
(C) Varying Refrigerant Functions (D) None of these
Ans: B
45. The gap between the false ceiling and the main ceiling is referred as :
(A) Supply air duct (B) Plenum
(C) Return air duct (D) Diffuser
Ans: B
46. During installation of split AC unit, what is the maximum vertical distance between indoor and outdoor units ?
(A) 20 feet (B) 30 feet (C) 15 feet (D) 40 feet
Ans: A
47. Water pressure cut out switch is installed in :
(A) Cooling tower line (B) Condenser water line
(C) Chilled water line (D) Both (B) and (C)
Ans: D
48. For leak testing, maximum test pressure for split AC system is :
(A) 70 PSIG (B) 150 PSIG (C) 100 PSIG (D) 200 PSIG
Ans: B
49. Cylindrical and needle roller bearings are commonly found in :
(A) Fans (B) Roller blades (C) Gear boxes (D) DC machines
Ans: C
50. Following are the methods of food preservation :
(A) Dehydration (B) Hydration (C) Canning (D) Both (A) and (C)
Ans: D
51. A motor has 4 poles, its RPM is :
(A) 1500 (B) 3000 (C) 750 (D) 500
Ans: A
52. Cooling performance test can only affectively done at ambient temperature above :
(A) 608F (B) 658F (C) 708F (D) 758F
Ans: D
53. If we use solar panels to run a car AC then the mileage of car will :
(A) Increase (B) Decrease
(C) Remain same as earlier (D) None of these
Ans: A
54. The main working substance in air conditioning is __________.
(A) Dry air (B) Moist air
(C) Dry ice (D) Water vapour
Ans: B
55. The temperature at which moisture condenses on a surface is called __________.
(A) Grains of moisture (B) Wet bulb temperature
(C) Dry bulb temperature (D) Dew point temperature
Ans: D
56. Scaling :
(A) Means attaching a scale to system pipes for the length measurement.
(B) Is an instrument for measuring the length.
(C) Deposition of a layer of chemicals inside a water carrying pipe in a heat exchanger.
(D) None of these
Ans: C
57. What is DDC in HVAC system ?
(A) Direct Decimal Classification (B) Direct Drive Control
(C) Direct Current (D) Direct Digital Control
Ans: D
58. Which valve allow fluid flow in only one direction ?
(A) Ball valve (B) Butterfly valve
(C) Check valve (D) Shut-off valve
Ans: C
59. Cylinder colour code for R 22 is :
(A) Light green (B) Orange
(C) Light gray (D) Light brown
Ans: A
60. In a scroll compressor :
(A) Both discharge and suction ports are located in the outer periphery
(B) Both discharge and suction ports are located near the center
(C) The discharge port is in the center and suction port is on the outer periphery
(D) The suction port is in the center and the discharge port is on the outer
Periphery
Ans: C
61. Piercing valves are used to tap a line for :
(A) Recovery (B) Testing (C) Charging (D) All of these
Ans: D
62. Window and split air conditioning units are used __________ compressor motors.
(A) CSR (B) RSIR
(C) CSIR (D) Shaded pole
Ans: A
63. Air flow quantities are measured in :
(A) FPM (B) PSI (C) BTU (D) CFM
Ans: D
64. Screwdrivers are classified according to :
(A) Length (B) Size of working tip
(C) Shape of working tip (D) All of these
Ans: D
65. Compressor crank shaft seal prevents __________ from escaping out.
(A) Air (B) Oil and Refrigerant
(C) Refrigerant (D) Oil
Ans: B
66. In a refrigeration cycle the heat is rejected by refrigerant at :
(A) Compressor (B) Evaporator (C) Expansion valve (D) Condenser
Ans: D
67. For brazing most commonly used flux is :
(A) Borax (B) Resin
(C) NHU4 (D) Carbonate chloride
Ans: A
68. Single phase motor is __________.
(A) Shaft starting (B) Self starting (C) Not self starting (D) None of these
Ans: C
69. Liquid receiver in a vapour compression system is used in __________.
(A) Suction line (B) Discharge line (C) Liquid line (D) Expansion line
Ans: C
70. HEPA stands for :
(A) High Energy Particulate Air (B) High Efficiency Particulate Air
(C) High Effective Pressurized Air (D) High Entry Particulate Air
Ans: B
71. ADP represents :
(A) Coil temperature (B) Coil pressure
(C) Coil point (D) None of these
Ans: A
72. GWP of R 134a refrigerant :
(A) 1700 (B) 1300 (C) 800 (D) 650
Ans: B
73. Atmospheric pressure at sea level is :
(A) 1.01325 bar (B) 14.7 PSI (C) 760000 Microns (D) All of these
Ans: D
74. Following is an HC refrigerant :
(A) R 600a (B) R 12 (C) R 22 (D) R 134a
Ans: A
75. Capillary tube is used for __________.
(A) Low capacity system (B) High capacity system
(C) Medium capacity system (D) None of these
Ans: A
76. Which instrument is used for measuring humidity ?
(A) Hydrometer (B) Thermometer
(C) Hygrometer (D) Anemometer
Ans: C
(A) 1500 (B) 3000 (C) 750 (D) 500
Ans: A
52. Cooling performance test can only affectively done at ambient temperature above :
(A) 608F (B) 658F (C) 708F (D) 758F
Ans: D
53. If we use solar panels to run a car AC then the mileage of car will :
(A) Increase (B) Decrease
(C) Remain same as earlier (D) None of these
Ans: A
54. The main working substance in air conditioning is __________.
(A) Dry air (B) Moist air
(C) Dry ice (D) Water vapour
Ans: B
55. The temperature at which moisture condenses on a surface is called __________.
(A) Grains of moisture (B) Wet bulb temperature
(C) Dry bulb temperature (D) Dew point temperature
Ans: D
56. Scaling :
(A) Means attaching a scale to system pipes for the length measurement.
(B) Is an instrument for measuring the length.
(C) Deposition of a layer of chemicals inside a water carrying pipe in a heat exchanger.
(D) None of these
Ans: C
57. What is DDC in HVAC system ?
(A) Direct Decimal Classification (B) Direct Drive Control
(C) Direct Current (D) Direct Digital Control
Ans: D
58. Which valve allow fluid flow in only one direction ?
(A) Ball valve (B) Butterfly valve
(C) Check valve (D) Shut-off valve
Ans: C
59. Cylinder colour code for R 22 is :
(A) Light green (B) Orange
(C) Light gray (D) Light brown
Ans: A
60. In a scroll compressor :
(A) Both discharge and suction ports are located in the outer periphery
(B) Both discharge and suction ports are located near the center
(C) The discharge port is in the center and suction port is on the outer periphery
(D) The suction port is in the center and the discharge port is on the outer
Periphery
Ans: C
61. Piercing valves are used to tap a line for :
(A) Recovery (B) Testing (C) Charging (D) All of these
Ans: D
62. Window and split air conditioning units are used __________ compressor motors.
(A) CSR (B) RSIR
(C) CSIR (D) Shaded pole
Ans: A
63. Air flow quantities are measured in :
(A) FPM (B) PSI (C) BTU (D) CFM
Ans: D
64. Screwdrivers are classified according to :
(A) Length (B) Size of working tip
(C) Shape of working tip (D) All of these
Ans: D
65. Compressor crank shaft seal prevents __________ from escaping out.
(A) Air (B) Oil and Refrigerant
(C) Refrigerant (D) Oil
Ans: B
66. In a refrigeration cycle the heat is rejected by refrigerant at :
(A) Compressor (B) Evaporator (C) Expansion valve (D) Condenser
Ans: D
67. For brazing most commonly used flux is :
(A) Borax (B) Resin
(C) NHU4 (D) Carbonate chloride
Ans: A
68. Single phase motor is __________.
(A) Shaft starting (B) Self starting (C) Not self starting (D) None of these
Ans: C
69. Liquid receiver in a vapour compression system is used in __________.
(A) Suction line (B) Discharge line (C) Liquid line (D) Expansion line
Ans: C
70. HEPA stands for :
(A) High Energy Particulate Air (B) High Efficiency Particulate Air
(C) High Effective Pressurized Air (D) High Entry Particulate Air
Ans: B
71. ADP represents :
(A) Coil temperature (B) Coil pressure
(C) Coil point (D) None of these
Ans: A
72. GWP of R 134a refrigerant :
(A) 1700 (B) 1300 (C) 800 (D) 650
Ans: B
73. Atmospheric pressure at sea level is :
(A) 1.01325 bar (B) 14.7 PSI (C) 760000 Microns (D) All of these
Ans: D
74. Following is an HC refrigerant :
(A) R 600a (B) R 12 (C) R 22 (D) R 134a
Ans: A
75. Capillary tube is used for __________.
(A) Low capacity system (B) High capacity system
(C) Medium capacity system (D) None of these
Ans: A
76. Which instrument is used for measuring humidity ?
(A) Hydrometer (B) Thermometer
(C) Hygrometer (D) Anemometer
Ans: C