Refrigeration and Air Conditioner Mechanic Questions and Answers
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Refrigeration and Air Conditioning Objective Questions
1. One tonne of refrigeration is equal to:
(A) 21 KJ/min
(B) 210 KJ/min
(C) 420 KJ/ min
(D) 620 KJ/min
2. A water cooler is uses the refrigerant :
(A) R 22
(B) R 717
(C) R 21
(D) R 134
3. What is the angle of point of centre punch?
(A) 90°
(B) 45°
(C) 60°
(D) 30°
4. The switch should control the line :
(A) Earth
(B) Neutral
(C) Phase
(D) Common
5. A compressor coupled to a motor externally is called :
(A) Sealed compressor
(B) Semi-sealed compressor
(C) Open type compressor
(D) None of the above
6. The purpose of a filter drier is to remove:
(A) Oil
(B) Moisture
(C) Gaskets
(D) Sludge
7. The storage capacity of a dissolved acetylene cylinder is :
(A) 6.0 m3
(B) 6.5 m3
(C) 7.0 m3
(D) 7.5 m3
8. The heart of refrigeration system is:
(A) Liquid receiver
(B) Condenser
(C) Evaporator
(D) Compressor
9. Velocity is measured in the units of:
(A) RPM
(B) CFM
(C) Kg Km2
(D) F.P.M
10. Colour code of ammonia refrigerant cylinder :
(A) Light blue
(B) Light green
(C) Orange
(D) Silver
11. Identify the zeotropic refrigerant from the following :
(A) R-40
(B) R407C
(C) R-22
(D) R12
12. Double cut file is made of :
(A) Cast steel
(B) Cast iron
(C) High carbon steel
(D) Spring steel
13. In air – refrigeration system, the coefficient of performance is :
(A) High
(B) Low
(C) Very high
(D) Moderate
14. A low side float valve maintains the level of refrigerant in :
(A) Flooded evaporator
(B) Evaporator
(C) Condenser
(D) Compressor
15. – 40° F is :
(A) – 40° C
(B) + 40° C
(C) 4.4 ° C
(D) – 10° C
16. The ball bearings of electrical motor are lubricated by :
(A) Grease
(B) Air
(C) Oil
(D) Water
17. Stabilizer used for 1.0 TR A/C is :
(A) 3 KVA
(B) 3.5 KVA
(C) 4 KVA
(D) 4.5 KVA
18. Which one of the following gives DC supply?
(A) Alternator
(B) Transformer
(C) Motor
(D) Dynamo
19. For checking the air movement, there is an instrument called :
(A) Thermometer
(B) Speedometer
(C) Anemometer
(D) Multimeter
20. The chemical formula of R134 is :
(A) C2H2F4
(B) C2Cl2F4
(C) CHl2F
(D) CHCl2
21. The thermostat for the window type air-conditioner is set at :
(A) 75°F
(B) 80°F
(C) 85°F
(D) 65°F
22. Auto defrost operated by :
(A) Timer switch
(B) Heating element
(C) Thermostat
(D) Evaporator fan
23. Brine solution density is checked by :
(A) Tachometer
(B) Anemometer
(C) Barometer
(D) Hydrometer
24. An ideal refrigerants is one whose boiling point is :
(A) High
(B) Medium
(C) Low
(D) Very High
25. The condenser in indirect system, condenses :
(A) Oil
(B) Refrigerant
(C) Brine
(D) Water
26. High side float valve is fitted on the condensing unit just after the :
(A) Receiver
(B) Compressor
(C) Condenser
(D) Evaporator
27. According to Ohm’s law I = :
(A) V.R
(B) R/V
(C) R.V
(D) V/R
28. When air is heated relative humidity :
(A) Decreases
(B) Increases
(C) Very high
(D) None of the above
29. Which chemical is used for condenser descaling?
(A) Phosphoric acid
(B) Sulphuric acid
(C) Citric acid
(D) Hydrochloric acid
30. Which refrigerant charged in car A.C?
(A) R11
(B) R22
(C) R134
(D) R12
31. The pipes which are used for absorption refrigeration system :
(A) Galvanised
(B) Steel
(C) PVC
(D) Brass
32. Convert from CFC 12 to HFC134, appliance, the compressor displacement will be
(A) Slightly larger
(B) Smaller
(C) Equal
(D) Double
33. Dry ice is
(A) Ammonia
(B) H2O
(C) Carbon mono-oxide
(D) Carbon dioxide
34. Relay is protection device used in :
(A) Evaporator
(B) Condenser
(C) Compressor
(D) Thermostat
35. Weak insulation can be checked by :
(A) Ammeter
(B) Tong tester
(C) Meggar
(D) Line tester
36. In window type air-conditioners the following expansion device used :
(A) Float valve
(B) Capillary tube
(C) Thermostatic expansion valve
(D) Hand valve
37. Freon 12 ideal pressure is :
(A) 2.0 Kg/Cm2
(B) 3.5 Kg/Cm2
(C) 2.5 Kg/Cm2
(D) 6.0 Kg/Cm2
38. The storage capacity of a oxygen cylinder is :
(A) 6.0 m3
(B) 7.01 m3
(C) 6.5 m3
(D) 7 m3
39. What is the range of flame temperature of oxygen-hydrogen gases?
(A) 1300 to 2000°C
(B) 2400 to 2100°C
(C) 2000 to 2200°C
(D) 3100 to 3300°C
40. Which type of flux is used for soldering G.l sheets?
(A) NH4Cl
(B) Resin
(C) ZnCl
(D) HCI
41. The cooling capacity of 1.0 TR is :
(A) 6000 BTU/Hr
(B) 18000 BTU/Hr
(C) 12000 BTU/Hr
(D) 24000 BTU/Hr
42. The atmospheric pressure at sea level is taken as :
(A) 1.03 Kg/Cm2
(B) 1.033 Kg/Cm2
(C) 1.02 Kg/Cm2
(D) 1.023 Kg/Cm2
43. The freezing temperature of water is
(A) 1°C
(B) -4°C
(C) -1°C
(D) 0°C
44. The mechanical fault in refrigerator system is :
(A) High voltage
(B) Over load protector burnt
(C) Condenser coil dirty
(D) Relay defective
45. Boiling point of R600, is :
(A) -15.8°C
(B) -11.8°C
(C) -14.8°C
(D) -10.8°C
46. The condenser coil type which used in deep freezer commonly:
(A) Flooded type
(B) Plate
(C) Natural draft
(D) Force draft
47. Internal energy of a substance is proportional to :
(A) Velocity
(B) Pressure
(C) Temperature
(D) None of the above
48. The closing of churner and top cover done air tight by :
(A) ‘0’ ring
(B) Gasket
(C) Seal
(D) Sticking tape
49. The thread angle of National fine thread is :
(A) 25°
(B) 40°
(C) 35°
(D) 45°
50. Select the ‘pitch’ of a medium hacksaw blade from the following:
(A) 1.8 mm
(B) 1.4 mm and 1.0 mm
(C) 1.0 mm and 4 mm
(D) 0.8 mm
Interview Questions On Refrigeration and Air Conditioning
51. Refrigerator compressor motor winding burnt out:
(A) High voltage
(B) Over load protector defective
(C) Loose connection
(D) Low voltage
52. Which of the following is not a desirable property of a good insulating material?
(A) Lightweight
(B) Odourless
(C) High heat conductivity
(D) Low coat
53. Compressor used in window A/c is :
(A) Rotary compressor
(B) Sealed compressor
(C) Reciprocating compressor
(D) Open type compressor
54. How many operations are in service valve?
(A) One
(B) Three
(C) Two
(D) Four
55. The most possible leakage spots in the refrigerator is :
(A) Capillary tube
(B) Condenser
(C) Brazing tube joints
(D) Evaporator
56. One Kilowatt is equal to :
(A) 1.34 H.P
(B) 1 H.P
(C) 1.66 H.P
(D) 1.5 H.P
57. It is an instrument used to measure high temperature :
(A) Psychrometer
(B) Themiomeber
(C) Pyrometer
(D) Micrometer
58. The operation of split A/c produces :
(A) High noise
(B) Low noise
(C) Medium noise
(D) No noise
59. Ball bearing can be removed by using :
(A) Ring spanner
(B) Mallet
(C) Puller
(D) Hammer
60. The metal wire which give good earth contact is :
(A) Copper
(B) GI
(C) Brass
(D) Aluminium
61. Name the temperature at which moisture condenses on a surface :
(A) Relative humidity
(B) Grains of moisture
(C) Dew point temperature
(D) Humidity
62. Name the correct tool which is used to cut wines :
(A) Wire cutter
(B) Tube cutter
(C) Shear
(D) Combination plier
63. Select the minimum number of diodes used in fulwave rectifier :
(A) Four
(B) One
(C) Three
(D) Two
64. The unit of pressure in SI system is :
(A) N/m
(B) N/m2
(C) N/m2
(D) N/m3
65. The amount of heat required in calories to raise the temperature of one gram of substance through 1°C is :
(A) Sensible heat
(B) Specific heat
(C) Latent heat
(D) B.t.u
66. Specify the thickness of a sheet metal having 18 SWG (Standard Wire Gauge)
(A) 1.02
(B) 1.63
(C) 1.01
(D) 1.22
67. The size of 1/2n copper tube is equal to :
(A) 12mm
(B) 14 mm
(C) 13 mm
(D) 16 mm
68. 360 litres refrigerator __________ compressor is used.
(A) 1/4 H.P
(B) 1/5 H.P
(C) 1/6 H.P
(D) 1/8 H.P
69. The temperature in degree centigrade for human comfort is :
(A) 15
(B) 17
(C) 19
(D) 21
70. If the vacuum level inside the refrigerator is 30 mm of Hg the moisture boiling temperature will be :
(A) 25°C
(B) 35°C
(C) 30°C
(D) 40°C
71. The size of the gasket is depends on :
(A) Width
(B) Length
(C) Thickness
(D) Area
72. The material with highest ductility :
(A) Cast iron
(B) Copper
(C) Tin
(D) Gold
73. To cool 20 litres of water from 32°C to 12.5°C in one hour. Calculate the amount of heat removed :
(A) 370 Kcal/Hr
(B) 380 Kcal/Hr
(C) 390 Kcal/Hr
(D) 400 Kcal/Hr
74. In large capacity air — conditioning applications the following expansion device is used
(A) Capillary tube
(B) Thermostatic expansion valve
(C) Float valve
(D) Automatic expansion valve
75. Relative humidity of air at the grill of an air-conditioner as compared to the room humidity is:
(A) Less
(B) More
(C) Same
(D) None of the above
76. The Global Warming Potential (GWP) of R134 is :
(A) 1500
(B) 1400
(C) 1300
(D) 1200
77. The solder wire used in electronic soldering melts at :
(A) 400°C
(B) 200°C
(C) 600°C
(D) 800°C
78. Select the material used to check the tightness of door gasket of a refrigerator :
(A) Gasket sheet
(B) Rubber sheet
(C) Paper sheet
(D) Plastic sheet
79. When a pressure switch cub-out, it will make the drive to :
(A) Stop
(B) Start
(C) Run on various speed
(D) Run slowly
80. When wet bulb and dry bulb temperature are equal the humidity is :
(A) 100%
(B) 90%
(C) 30%
(D) 60%
81. Sensible heat factor is:
(A) Sensible heat/ Latent heat
(B) Total heat/ Sensible heat
(C) Latent heat/Sensible heat
(D) Sensible heat/Total heat
82. Amount of heat required to raise the temperature of one pound of water through 1°C is called:
(A) C.H.U
(B) B.T.U.
(C) Calorie
(D) Specific heat
83. Oil separator is filled in between :
(A) Condenser and evaporator
(B) On the suction line
(C) Compressor and condenser
(D) At the receiver outlet
84. H.F.C. should not vent into atmosphere because :
(A) It is flammable in atmospheric temperature
(B) It has high global warming potential
(C) It is highly toxic
(D) It is very costly gas
85. Process of changing solid into its vapour state without passing through liquid state is :
(A) super heating
(B) sublimation
(C) subcooling
(D) triple point
86. Latent heat of fusion of ice is :
(A) 335 KJ/kg
(B) 144 BTU/lb
(C) 80 kilo calories/kg
(D) all of the above
87. Sling psychrometer is used to measure :
(A) only dry bulb temperature
(B) dry and wet bulb temperature
(C) only wet bulb temperature
(D) relative humidity
88. In air refrigeration refrigerating effect is produced by
(A) compressing air
(B) subcooling
(C) storing of liquid refrigerant
(D) condensing gas
89. Accumulator is provided for :
(A) storing of unvapourized liquid
(B) exchange of heat
(C) expanding air
(D) super heating
90. In air conditioning of aeroplanes the refrigerant used is:
(A) Ammonia
(B) Air
(C) Freon 12
(D) Water
91. Select the wrong characteristics of refrigerant :
(A) low latent heat
(B) high thermal conductivity
(C) low boiling point
(D) none of these
92. The function of duct in air conditioning unit is :
(A) air cooling
(B) air dryinx
(C) air cleaning
(D) air distributing
93. Commonly used refrigerant in commercial ice plant is :
(A) Ammonia
(B) Air
(C) Freon 12
(D) CO2
94. The C.O.P. of a domestic refrigerator in comparison to domestic air conditioner will be
(A) More
(B) Less
(C) Same
(D) unpredictable
95. An Air washer can work as :
(A) Humidifier
(B) Dehumidifier
(C) Filter
(D) All the above
96. The brine is always used as a secondary refrigerant in :
(A) cold storage
(B) milk chilling plant
(C) ice plant
(D) none of these
97. In winter air conditioning the process used is :
(A) Dehumidification
(B) Heating and humidification
(C) Humidification
(D) Cooling and dehumidification
98. At which point °C scale and °F scale will be same
(A) 49°
(B) 0°
(C) 273°
(D) 40°
99. Sub cooling is a process of cooling the refrigerant in vapour compression refrigeration system before :
(A) Evaporation
(B) Throttling
(C) Condensation
(D) Compression
ITI Refrigeration And Air Conditioning Question Bank Pdf
100. The milk is stored at a temperature of :
(A) -5°C
(B) 10°C
(C) 0°C
(D) 4°
101. Absolute zero temperature is taken as :
(A) -27 3°C
(B) 273°C
(C) 237°C
(D) 0°C
102. A thermostatic expansion valve function with : –
(A) suction pressure
(B) discharge pressure
(C) discharge temperature
(D) suction temperature
103. For ammonia refrigerating system the tubes of a shell and tube condenser are made of :
(A) Copper
(B) Aluminium
(C) Steel
(D) Brass
104. Convert from CFC 12 to HFC 134 A the compressor displacement will be :
(A) Smaller
(B) equal
(C) slightly larger
(D) double
105. The type of condenser used in water cooler :
(A) natural draft
(B) forced draft
(C) evaporative
(D) water cooled
106. Pump down the system for :
(A) more cooling effect
(B) to check compressor efficiency
(C) gas charging
(D) to attend maintenance in low side
107. Purging is done :
(A) after gas charging
(B) before gas charging
(C) before vacuumizing
(D) before preseurising
108. The refrigerant enters in the condenser by the :
(A) top side
(B) last coil
(C) bottom side
(D) middle tube
109. One ton refrigeration is equal to:
(A) 210 kj/min
(B) 12600 kj/hour
(C) 3.5 kj/sec
(D) all of the above
110. Liquid charged in thermostatic expansion valves sensing bulb is :
(A) Alcohol
(B) same refrigerant
(C) mercury
(D) nitrogen
111. Solenoid valve operated by :
(A) Electrically
(B) Hand
(C) gas pressure
(D) oil pressure
112. The colour of the flame of halide torch in case of leakage of Freon refrigerant will change to
(A) Yellow
(B) Red
(C) bright green
(D) orange
113. Which type of valve is used in a reciprocating refrigeration compressor?
(A) rotary valve
(B) poppet valve
(C) ring plate
(D) glob valve
114. The presence of frost on the cooling coils of the evaporator of a refrigeration system :
(A) increases the compressor pressure
(B) act as the insulator and decreases the heat transfer rate
(C) makes the compressor run for comparatively short durations
(D) reduce the life of cooling coils
115. Dry ice is :
(A) solidified carbondioxide
(B) ice free from dissolved air and gases
(C) ice free from impurities
(D) ice made from transparent distilled water
116. Which of the following machines can be used to obtain refrigeration at places where there is no electric power?
(A) air refrigeration
(B) steam jet refrigeration
(C) vapour compression
(D) vapour absorption
117. Rectifiers are used for converting :
(A) voltage into current
(B) AC to DC
(C) DC to AC
(D) voltage in to velocity
118. The operation theatre in a hospital is to be air conditioned suggest the percentage of outside air being circulated in the theatre :
(A) Zero
(B) 20
(C) 50
(D) 100
119. The difference between D.B.T. and W.B.T. is called :
(A) wet bulb depression
(B) dew point depression
(C) effective temperature
(D) adiabatic saturation temperature
120. The absolute zero temperature corresponds on the condition when :
(A) all the substances exit only as solids
(B) volume of a gas reduces to zero
(C) kinetic energy of gas molecules become zero
(D) no pressure is exerted by the gas
121. The oil used with 134 A refrigerant is :
(A) Mineral oil
(B) Capilla D
(C) Polyol ester oil
(D) Lubricating oil
122. Cripser temperature of refrigerator is equal to :
(A) 0°C
(B) 8°C
(C) -5°C
(D) None of the above
123. Auto defrost operated by :
(A) Evaporator fan
(B) Thermostat
(C) Timer switch
(D) Heating element
124. Dehydrator is installed in the :
(A) liquid line
(B) discharge line
(C) suction line
(D) charging line
125. The device which used to find relative humidity :
(A) Pyrometer
(B) Anemometer
(C) Hydrometer
(D) Hygrometer
126. Chemical name of Freon 22 is :
(A) Dichloro difluom methane
(B) Monochloro difluoro methane
(C) Trichloro monofluoro methane
(D) Dichloro monofluoro methane
127. The capacity of visible cooler is expressed in:
(A) cubic feet
(B) litres
(C) k.cal/TR
(D) tons of refrigeration
128. Which of the following refrigerant has the lowest boiling point?
(A) Carbon dioxide
(B) Ammonia
(C) Sulphur dioxide
(D) Freon 12
129. HFC 134 A appliance has capillary length when compare to CFC unit :
(A) 10% to 20% more
(B) 20% short
(C) 50% longer
(D) same length
130. The effectiveness of the cooling tower is dependent on :
(A) Dry bulb temperature of the air
(B) Direction of the flow of air
(C) Wet bulb temperature of the air
(D) None of the above
131. Milky white ice obtained if :
(A) impurities are present in water
(B) due to the presence of CO2
(C) by keeping in an insulated chamber
(D) air is present in it
132. In a shell and coil condenser:
(A) water flows in the shell and refrigerant in the coil
(B) only refrigerant flows through the shell as well as coil
(C) only water flows through the shell as well as coil
(D) water flows in the coil and the refrigerant in the shell
133. In a thermal electric expansion valve which senses the suction temperature is :
(A) Transformer
(B) Thermister
(C) Thermostat
(D) Rheostat
134. In a flooded evaporator which of the following types of expansion. device is employed :
(A) float valve
(B) capillary tube
(C) automatic expansion valve
(D) thermostatic expansion valve
135. In an ice plant the function of brine agitator is :
(A) to increase COP
(B) to reduce compressor power
(C) to obtain uniform temperature
(D) to super heat the refrigerant gas
136. In an air conditioning system the comfort conditions are defined by :
(A) 15°C DBT 90% RH
(B) 25°C DBT 35% RH
(C) 20°C DBT 80% RH
(D) 22°C DBT 60% RH
137. The electrical component of automobile air conditioner allows to engage and disengage the compressor from the thermostat :
(A) Rheostat
(B) Thermostat
(C) Fuse
(D) Magnetic clutch
138. Sum of atmospheric pressure and gauge pressure is called :
(A) Total pressure
(B) Absolute pressure
(C) Normal pressure
(D) Natural pressure
139. The diode used for voltage regulation is :
(A) Rectifier diode
(B) Signal diode
(C) Zener diode
(D) Vari cap diode
140. The specific humidity is the mass of water vapour present in
(A) 1 kg of dry air
(B) 1m3 of dry air
(C) 1 m3 of wet air
(D) 1 kg of wet air
141. Which one of the following oxy fuel gas flames has the highest flame temperature?
(A) Oxy hydrogen
(B) Oxy acetylene flame
(C) Oxy coal gas flame
(D) Oxy LPG flame
142. A micrometer has a positive error of 0.02 MM. What is the correct reading when the micrometer measures 25.37 MM :
(A) 25.35 MM
(B) 25.39 MM
(C) 25.43 MM
(D) 25.41 MM
143. One micron of vacuum is equal to :
(A) 0.1 MM Hg
(B) 0.001 MM Hg
(C) 0.01 MM Hg
(D) 0.0001 MM Hg
144. Start the compressor without relay to short :
(A) C and S terminal
(B) C and R terminal
(C) S and R terminal
(D) Compressor body and S terminal
145. There is no relay and starting capacitor in :
(A) CSR circuit
(B) RSIR circuit
(C) CSIR circuit
(D) PSC circuit
146. Stabilizer used for 1.0 TR AC is :
(A) 2 KVA
(B) 3 KVA
(C) 4 KVA
(D) 5 KVA
147. Select the period of interval for a defrost cycle in a frost free refrigerator :
(A) once in 12 hours
(B) once in 24 hours
(C) once in 36 hours
(D) once in 48 hours
148. Select the boiling point of refrigerant 134 A at 1 atmosphere :
(A) -3 l.5°C
(B) -29.8°C
(C) -26. 1°C
(D) -11.B°C
149. Most important property of insulating material is :
(A) Odourless
(B) easy to handle
(C) light in weight
(D) low conductivity
150. The component which control the bimetal thermostat is :
(A) Defrost heater
(B) Fan motor
(C) Overload protector
(D) P.T.C. Relay
Refrigeration and Air Conditioning Previous Year Question Papers
151. HC refrigerant using systems should be vacuumized upto :
(A) 2000 Microns Hg
(B) 500 Microns Hg
(C) 100 Microns Hg
(D) 1000 Microns Hg water
152. When compare to CFC 12 the charge of 134 A will be
(A) 90% to 95%
(B) 25% extra
(C) same weight
(D) twice quantity
153. The swash plate compressor is most frequently used in
(A) Refrigerators
(B) Window air conditioners
(C) Split air conditioners
(D) Car air conditioners
154. Which of the following refrigerant has the lowest freezing point?
(A) Ammonia
(B) Freon-11
(C) Freon-22
(D) Freon-12
155. A mechanical shaft seal is necessary in a :
(A) open type compressor
(B) hermetic rotary compressor
(C) semi hermetic compressor
(D) hermetic reciprocating compressor
156. While recovery the cylinder can be charged maximum upto :
(A) 95%
(B) 80%
(C) 60%
(D) 45%
157. The component common for vapour compression and vapour absorption system is
(A) Rectifier
(B) Generator
(C) Condenser
(D) Absorber
158. Modification of R.12 to R 134 A refrigerant is called :
(A) Recharzins
(B) Retrofit
(C) Recovery
(D) none of the above
159. The fire micron film is named as :
(A) catch air filter
(B) bag filter
(C) rough filter
(D) fine filter
160. Water inlet flow of the water cooler is controlled by :
(A) expansion valve
(B) pressure regulating valve
(C) solenoid valve
(D) float valve
