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Refrigeration > Final > Flashcards

Final Flashcards

1
Q

an obstructed expansion valve may be indicated by an incompletely cooled evaporator and

A

frosting at the evaporator inlet

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2
Q

when liquid reached the compressor of a fridge system through the suction line, the condition is called

A

flooding back (slugging)

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3
Q

the refrigerants referred to as CFCs are

A

fully halogenated

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4
Q

excessive oil foaming in the crankcase of a fridge compressor can result in

A

overheated compressor bearings

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5
Q

if you find an extremely large leak while using a halide torch, the flame will

A

go out

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6
Q

in a fridge system, the heat normally producing the flash gas at the TEV, is obtained from

A

the portion of liquid refrigerant which does not flash

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7
Q

what device will indicate proper operation of a fridge system dryer

A

moisture indicator

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8
Q

lube oil should have

A

a low pour point

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9
Q

a compound gauge is typically installed on the

A

suction side of a compressor

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10
Q

what is the safest device for testing for ammonia leaks?

A

litmus paper

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11
Q

increasing head pressure in a fridge system without any corresponding change in the cooling water inlet temp would prob be caused by

A

air and non-condensibles gases in the condenser

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12
Q

alkylbenzene is miscible and suitable for use with

A

r-22

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13
Q

if an expansion valve is adjusted for too a superheat value

A

too much liquid will be passed back to the compressor

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14
Q

during the operation of a large, multi-box system, using a fixed capacity compressor, only 2 of 5 boxes are being cooled. if 2 more boxes started cooling

A

low side pressure would temp increase

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15
Q

the water regulating valve installed in a system is operated by the

A

compressor discharge pressure

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16
Q

recovery small appliance after nov 1993

A

90%

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17
Q

constant superheat is maintained at the evaporator outlet of a coil by a

A

TEV

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18
Q

ammonia is lighter than air and if a leak should occur it’s concentration will be

A

of minimum importance during venting

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19
Q

air trapped in a system using a water cooled condenser is usually indicated by

A

unusually high head pressure when compared with existing temp of liquid refrigerant

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20
Q

foaming of the oil in a refrigerant compressor crankcase is caused by

A

refrigerant boiling out of solution from the lube oil

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21
Q

overcharging an air-cooled system will cause the

A

compressor to short cycle

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22
Q

the amount of refrigerant admitted to the evaporator is directly related to

A

the superheat of the refrigerant in the tail coil

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23
Q

during tests to on a compressor running excessively, it is determined that the refrigerated space temp is nearly normal, the suction pressure is slightly high, and the head pressure is low. you suspect

A

leak door gaskets

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24
Q

what occurs if the power element of a TEV fails

A

the valve will move towards the closed position

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25
Q

a shortage of refrigerant is indicated by

A

bubble in the sight glass

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26
Q

when opening or closing service and line valves you

A

must open the seal cap

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27
Q

a compound gauge measures

A

pressure and vacuum

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28
Q

what is an accepted method for testing a TEV

A

place the sensing bulb in ice water and warm by hand. observe flow through and temp change at suction line

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29
Q

when is oil reading most accurate

A

shutdown following a prolonged period of operation

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30
Q

1st step in repairing known leaking system

A

look for oil

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31
Q

if head pressure in reciprocating compressor is excessive

A

the high pressure cutout switch should operate before the relief valve

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32
Q

the rate of heat transfer from a hot region to a cold region is affected most by

A

temp diff between regions

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33
Q

moisture in refrigerant may

A

freeze on the expansion valve seat and reduce the flow of liquid refrigerant

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34
Q

the compressor has blown the shaft seal, what do first

A

secure compressor and close suction and discharge valves

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35
Q

what piping material is used in extra heavy duty systems

A

steel

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36
Q

liquid line, thermostatically controlled, solenoid valve operates in response to

A

temp of box

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37
Q

a system equipped with reciprocating compressor and water cooled condensing unit is overcharged, resulting in high head pressure caused by

A

refrigerant flooding the condenser

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38
Q

ammonia should be added at

A

the high side of system

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39
Q

small obstruction in TEV will result in

A

suction pressure fluctuation

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40
Q

refrigerant with oil in solution will

A

have a higher boiling temp at a given pressure than pure refrigerant

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41
Q

sight glass in liquid line will indicate

A

condition of refrigerant charge and moisture in system

42
Q

how to prevent a system from working while under repair

A

lock out electrical circuit

43
Q

compressor in air cooled system is short cycling on high pressure cutout switch because

A

system is overcharged with refrigerant

44
Q

compressor in water cooled system is short cycling on high pressure cutout switch because

A

high pressure cutout switch is improperly adjusted

45
Q

if temp of ammonia gas in discharge piping of condenser remains above 266 degrees F

A

vapor will cease to condense

46
Q

units over 20 cu ft capacity require what for repair

A

a gas mask or SCUBA

47
Q

overfilling a container is extremely dangerous because high pressure called

A

hydro-static pressure of expanding liquid

48
Q

what valve should be closed when adding ammonia

A

king valve

49
Q

when taking readings at suction service valve of operating compressor

A

temp and pressure is required as refrigerant is superheated

50
Q

condenser cooling water regulating valve is directly controlled by the

A

compressor discharge pressure

51
Q

what copper alloy is commonly used in heat exchanges and has high resistance to corrosion

A

cupro-nickel

52
Q

what is a suitable replacement for r-11

A

r-123

53
Q

to correct slugging and flooding

A

adjust expansion valve

54
Q

excessive charge of refrigerant in air cooled system can cause

A

higher than normal discharge pressure with normal box temp

55
Q

if a liquid line strainer becomes clogged, it will be indicated by

A

loss of refrigeration effect in box

56
Q

when hot gas defrosting a system, to avoid slugging, use the

A

re-evaporator

57
Q

refrigerant leaving the metering device is

A

saturated liquid/vapor mixture

58
Q

recovered burned out refrigerant will be

A

sent to reclamation facility for processing

59
Q

moisture is removed from cfc-12 using a recycler by

A

using a dehydrator cartridge

60
Q

what is characteristic of the liquid charged power element used in a TEV

A

the sensing bulb is never emptied of liquid refrigerant

61
Q

refrigeration system compressor crankcase sweating is an indication of

A

excessive circulation of lube oil through the system

62
Q

what refrigerant will normally require water cooled compressor

A

ammonia

63
Q

if a system is short cycling on high head pressure, you should

A

check for proper water flow through the condenser

64
Q

noise in a compressor can be caused by

A

worn bearings and piston pins, slugging, too much oil in circulation

65
Q

ammonia vapors can

A

cause death in low concentration, will dissolve in perspiration and cause burns, will burn or explode

66
Q

r-12 is toxic when

A

in contact with an open flame

67
Q

if discharge valves are leaking badly, the compressor will

A

run continuously

68
Q

where is the greatest amount of superheat

A

the compressor discharge

69
Q

a purge recovery system is used in a centrifugal air conditioning or fridge system to

A

purge non-condensible gases without losing refrigerant

70
Q

if the suction line between the evaporator and compressor is frosting up, the cause may be due to the TEV

A

thermal bulb coming loose from the suction line

71
Q

each pressure vessel containing refrigerants, which may be isolated, shall be

A

protected by a relief valve set to relieve at a pressure not exceeding the maximum allowable working pressure of the vessel

72
Q

a multi evaporator coil unit is equipped with an evaporator back pressure regulating valve. it must be bypassed when pumping down for repair be reduced suction pressure would cause the valve to

A

close

73
Q

how does a solenoid valve differ from a modulating valve

A

solenoid is open or closed, modulating is position by the electrical signal

74
Q

what is essential when installing a new TEV

A

accurate temp and suction pressure gauge

75
Q

the oil separator is located

A

between the compressor discharge valve and the condenser

76
Q

the sensing bulb doesn’t need insulation if the bulb is installed

A

in the cooled air stream

77
Q

high suction pressure in a compressor is caused by

A

the TEV be opened too wide

78
Q

when replacing the TEV

A

apply light film of oil to prevent oxidation

79
Q

temp in box is controlled by adjusting the thermostat connected to the

A

liquid line solenoid

80
Q

when removing air from system, all refrigerant should be

A

pumped to reciever

81
Q

leaking suction valves in a compressor are indicated by

A

higher than normal suction pressure

82
Q

oil separators serve to

A

return oil entrained in vapor back to the compressor crankcase

83
Q

constant hissing at the TEV indicates

A

a lack of refrigerant

84
Q

chemical moisture indicators in a sight will

A

change color if there is moisture

85
Q

if a relief valve opens on a compressor discharge line, it discharges high pressure vapor to

A

the suction side of the compressor

86
Q

refrigerant entering the compressor is

A

superheated vapor

87
Q

short cycling is

A

frequent starting and stopping

88
Q

excessive oil foaming in crankcase will occur when

A

the compressor starts after a long idle period

89
Q

TEV have what to change size

A

internal restrictors of different sizes

90
Q

if suction pressure in a compressor is below normal, it may be

A

a fouled compressor suction strainer

91
Q

if a compressor is short cycling on the low pressure cutout switch, the cause is

A

TEV strainer is fouled

92
Q

compressor is short cycling on high head pressure, cooling sea water is 72 degrees

A

check for sufficient flow through condenser

93
Q

low pressure cutout switch is actuated by

A

pressure changes in suction line

94
Q

all systems are protected with a

A

high pressure cutout

95
Q

temp in the evaporator coil depends on

A

refrigerant pressure in the evaporator

96
Q

introduce refrigerant on low side through

A

suction service valve as vapor

97
Q

what is not on the high side

A

accumulator

98
Q

TEV bulb is located

A

neat evaporator coil outlet

99
Q

safety heads in compressor are held by

A

heavy coil springs

100
Q

cylinders are what max weight

A

50 lbs

Refrigeration (1 decks)

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