Maultiple Choice Questions for Refrigeration

7/30/2019 Maultiple Choice Questions for Refrigeration

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REFRIGERATION

1)During standstill liquid may condense in the crankcase or oil separator. Why is it important to heat up

the oil before start?

a)The compressor will run better.

b)It should never be done.

c)To avoid the compressor-oil disappearing from the crankcase during starting.

d)Compressor oil regulating system will operate better.

2) Personnel working with refrigeration systems, and subject to the exposure of refrigerants should

wear

a)face shield

b)a respirator

c)rubber gloves

d)an all purpose gas mask

3) People familiar with ammonia refrigeration systems become accustomed to its odor and may forget

that the vapors

a)in a low concentration can cause death

b)will dissolve in pespiration and cause caustic burns

c)will burn or explode

d)all of the above

4) When the relief valve opens it discharges high pressure refrigerant vapor to the

a)liquid strainer

b)refrigerant inlet of the condenser

c)inlet side of the evaporator

d)suction side of the compressor

5) In a direct expansion type multi-box refrigeration system, the compressor is set up to cycle on and offby the

a)pressurestat

b)high pressure cut out

c)solenoid valve


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d)low pressure cut out switch

6) Which of the listed operations will cause an automatically controlled refrigeration compressor to

restart?

a)closing of the solenoid valve

b)closing of the expansion valve

c)an increase in the suction pressure

d)decreasing the suction pressure

7) In a direct expansion type cargo refrigeration system, a box is normally changed from chill to freeze

by adjusting the

a)hand expansion valve

b)compressor suction valve

c)solenoid bypass

d)back pressure regulating valve

8)Which of the problems listed could be indicated if a sight glass in the refrigerant liquid line is full of

bubbles?

a) excess refrigerant charge

b)faulty expansion valve

c)insufficient refrigerant

d)solenoid valve stuck open

9) A liquid indicator sight glass is useful in determining whether or not a refrigeration system is

sufficiently charged. It is generally located in the

a)high pressure liquid line

b)low pressure liquid line

c)high pressure vapor line

d)low pressure vapor line

10) If the refrigeration compressor crankcase is sweating, the cause may be due to

a)a shortage of refrigerant

b)the compressor running continuously

c)liquid refrigerant returning to the compressor


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d)the compressor short cycling on the high pressure cutout

11) If a refrigerating compressor crankcase is sweating, the trouble could be caused by

a)excessive superheat

b)a minor amount of air in the system

c)normal oil circulation with the refrigerant

d)the expansion valve being stuck in the open position

12) Frosting or sweating of the suction line of a reciprocating refrigeration compressor indicates a

condition which could result in severe damage due to

a)minor amout of oil in the refrigerant

b)liquid slugging


d)a failed heat interchanger

13) Refrigeration system compressor crankcase sweating is an indication of

a)insufficient lube oil circulating throgh the system

b)excessive circulation of lube oil through the system

c)insufficient refrigerant in the system

d)an overworked compressor

14) Sweating of the refrigeration system compressor crankcase is caused by

a)too much superheat

b)insufficient superheat

c)suction pressure too low

d)excessive refrigerant returning to the compressor

15) Oil separators installed in refrigeration systems serve to

a)remove excess oil from the system

b)remove oil entrained in high pressure liquid line

c)return oil entrained in refrigerant vapor back to the compressor crankcase

d)all of the above

16) The oil separator (trap) used in a shipboard refrigeration system is located between the


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a)compressor discharge valve and the condenser

b)condenser and the receiver

c)receiver and the king valve

d)receiver and the expansion valve

17) The purpose of the refrigeration system low pressure cutout switch is to

a)protect the compressor from liquid flood back

b)protect the compressor from low discharge pressure

c)start and stop the compressor upon system demand

d)-start the compressor after a drop in the evaporator pressure

18) The sensing line for the low pressure cutout switch to a refrigeration system is located

a)in the chill box

b)before the receiver

c)on the suction side of the compressor

d)on the discharge side of the compressor

19) The refrrigeration system low pressure cutout switch is actuated by

a)an electric system manager

b)a sensing bulb at the tail coil of the evaporator

c)pressure changes in the suction line

d)failure of the king solenoid valve

20)When you adjust thermostatic expansion valve

a)refrigerant must be bled off the sensing line before adjustments are made

b)all refrigerant must be pumped into the receiver before adjustments are made

c)time must be allowed for conditions to stabilize in the evaporator before further adjustments are

made

d)all refrigerant must be routed through the dehydrator while changing the superheat setting

21) Low compressor head pressure in a refrigeration system can be caused by

a)insufficient condenser cooling water

b)excessive condenser cooling water


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c)air in the refrigeration system

d)excessive refrigerant in the system

22) Which of the problems listed would cause the discharge temperature of an Freon refrigeration

compressor to increase?

a)thermal expansion valve frozen open

b)suction gas heat exchanger bypassed

c)condenser clogged or fouled

d)high pressure cutout switch inoperative

23) One cause of high head pressure occurring in a refrigeration system can be

a)insufficient cooling water flow to the condenser

b)a low refrigerant charge in the system

c)the liquid valve is open too much

d)high evaporator superheat

24) If the head pressure of a reciprocating refrigeration compressor is excessive,

a)the relief valve should open before the high pressure cutout

b)the relief valve should open and allow the excess refrigerant to flow to the receiver

c)the high pressure cutout switch should operate before the relief valve opens

d)you should close in on a suction valve

25) If the refrigeration compressor was developing higher than normal discharge pressure, this could be

a result of

a)air or noncondesable gases in the system

b)leaking discharge valves

c)leaking suction valves

d)liquid refrigerant flooding back from the cooling coil

26) If the water failure switch should fail to shut down the refrigeration compressor, the refrigerant

pressure will build up in the high pressure side of the system to the point where the

a)compressor discharge valves would be damaged

b)condenser tubes would rupture

c)system relief valve would open


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d)high pressure cutout switch would function

27) High suction pressure to a refrigeration system compressor is caused by

a)the expansion valve is insufficiently opened

b)the expansion valve being open too wide

c)the king valve is insufficiently open

d)a dirty dehydrator

28) If a refrigeration compressor had developed a high suction pressure, the problem could be a result

of

a)a minor accumulation of air or uncondensable gases in the system

b)a leaking king valve

c)a clogged subcooler

d)liquid refrigerant flooding back from the cooling coil

29) Which of the conditions listed could cause excessively low refrigerant pressure at the compressor

suction?

a)insufficient flow of condenser cooling water

b)the system is low on refrigerant

c)the solenoid valve to the chill box is "frozen" in the open position

d)the high pressure cutout switch is inoperative

30) Which of the conditions listed may be an indication of an excessive amount of refrigerant circulating

through the system?

a)sweating of the compressor crankcase

b)colder than normal solenoid valve

c)frosting of the evaporator

d)weeping at the purge valve

31) Leaking suction valves in a refrigeration compressor are indicated by

a)higher than normal suction pressure

b)lower than normal suction pressure

c)lower than normal evaporator temperature

d)noticeable increase in compressor noise


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32) If the discharge valves on the refrigeration compressor are leaking badly, the compressor should

a)run continuously

b)not start

c)have high discharge pressure

d)short cycle on the high pressure switch

33) If a refrigeration system were short of refrigerant, the condition would result in

a)continuous running of the compressor

b)high suction pressure

c)high discharge pressure

d)short cycling of the compressor on the water failure switch

34) A warmer than normal compressor suction line might be caused by

a)insufficient lubrication

b)insufficient refrigerant

c)excess refrigerant

d)excessive opening of the expansion valve

35) what causes the refrigeration system to short cycle on a HP cutout-

a)dischg valve leaking

b)pressure cutout set incorrectly

c)system overcharged with refrigerant

d)insufficient cooling water.

36) When purging a refrigeration system, the compressor is

a)running

b)running but the condenser is secured.

c)shut down

d)running with the bypass open

37) The refrigerant temperature is at the maximum before it enters the

a)expansion valve

b)compressor


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c)condenser

d)evaporator

38) The solenoid valve controls the

a)pressure in the evaporator coils

b)amount of refrigerant entering the evaporator

c)flow of refrigerant to the expansion valve

d)amount of circ water to the condenser

39) Closing the solenoid valve will stop the compressor through the

a)low water pressure cut out switch

b)bypass relief valve

c)LP cutout switch

d)HP cutout switch.

40) The temperature bulb of the thermo expansion valve is attached to the

a)icebox coil

b)evaporator coil outlet

c)evaporator coil inlet

d)wall of the ice box

41) The temperature bulb of a solenoid valve is attached to the-

a)icebox coil

b)wall of the icebox

c)evaporator coil inlet

d)evaporator coil coutlet

42) The suction pressure regulating valve

a)cuts in the compressor

b)maintains the back pressure in the evaporator coils

c)cuts out the compressor

d)controls the expansion valve

43) The cooling water regulator is automatically actuated by


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a)discharge pressure of the refrigerant

b)temperature of the refrigerant

c)an electric relay

d)a thermo relay

44) The LP control switch

a)is a safety device

b)actuates the coling water

c)cuts out the compressor to maintain proper flow.

d)regulates the king valve

45) A hot crankcase and cylinder head accompanied by low suction pressure would be caused by

a)excess refrigerant


c)air in the system

d)stuck discharge valve

46) When securing a system the first step would be to

a)open bypass valve

b)close receiver king valve

c)open solenoid valve

d)cut out compressor on HP

47) External frost on inlet of expansion valve indicates-

a)expansion valve plugged or dirty

b)head pressure too high

c)refrigerating comnpartment too cold

d)air in system

48) When the crankcase is cooler than the suction line it is because-

a)too much refrigerant


c)expansion valve open too wide


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d)suction valve leaking

49) Closing the solenoid valve stops the compressor through the

a)HP cutout switch

b)low water pressure cutout switch

c)low pressure cutout switch

d)high water pressure cutout switch.

50) Tubing joints are

a)brazed

b)welded

c)screwed

d)silver soldered

51) Which of the following would cause a compressor to run continiously-

a)LP switch jammed

b)HP switch jammed

c)clogged strainer

d)defective thermal bulb

52) The solenoid valve is a-

a)pressure controlled stop valve

b)temperature controlled stop valve

c)Freon controlled check valve

d)none of the above

53) The scale trap is located between the

a)compressor and oil separator

b)expansion valve and evaporator coils

c)king valve and expansion valve

d)evaporator coils and compressor

54) Too low suction pressure could be caused by-

a)too much oil in the system


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b)dirty scale traps

c)shortage of refrigerant gas

d)any of above

55) Sweating of a crank case is caused by-

a)too much oil in the system

b)too much superheat

c)insufficient superheat

d)expansion valve hung up

56) Slugging is usually caused by-

a)too much refrigerant in the system

b)too much oil in the system

c)expansion valve not operating properly

d)too much cooling water to condenser.

57) A device for holding open the suction valve and drawing gas from the suction manifold and returning

it to the suction line without compressing is called-

a)relief valve

b)cylinder unloader

c)suction line bypass

d)dischg line bypass.

58) A hot suction line is caused by-

a)insufficient lubrication

b)insufficient refrigeration

c)too much refrigerant

d)expansion valve closed too much

59) If a solenoid valve is closed accidentally , the compressor would be stopped by-

a)automatic trip

b)low water cutout switch

c)low pressure cutout switch


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d)HP cutout switch.

60)If the compressor short cycles on HP cutout, check for

a)too much refrigerant in the system

b)condenser tubes need cleaning

c)system is starved of cooling water

d)all of above

61) If the compressor short cycles on LP cutout- the trouble could be

a)too much frost on evaporator coils

b)dirty traps and strainers

c)lack of refrigerant

d)any of above

62) If the compressor were to run continiously without lowering the temperature-the trouble could be

a)leaky dischg valves

b)leak in the system


d)any of above

63) Which of the following would cause a high suction pressure-

a)expansion valve open too wide

b)dirty dehydrator

c)king valve not open wide enough

d)expansion valve not open wide enough

64) If a compressor runs continiously , the cause might be-

a)clogged scale trap

b)stuck HP switch

c)defective thermal bulb

d)stuck LP switch.

65) Low suction pressure is caused by

a)expansion valve causing flooding back


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b)solenoid valve not functioning properly

c)leaky compressor suction valves

d)air in system

66) If the compressor dischg temp is higher than the receiver temperature-

a)add more refrigerant to the system

b)decrease the amount of cooling water to the condenser

c)increase the amount of cooling water to the condenser

d)remove some of the refrigerant from the system

67) Air can be prevented from entering into the system by-

a)running the refrigerant through an aereator

b)keeping the dehydrator clean at all times

c)keeping all glands and stuffing boxes on the HP side tight.

d)keeping all glands and stuffing boxes on the LP side tight

68) If there is too much Freon in the system

a)the safety valve will discharge

b)the compressor will short cycle

c)the compressor will run continiously

d)it will mix with the oil in the crankcase

69) Frost on the outside of the thermal expansion valve is may be caused by-

a)too much superheat

b)air in the system

c)moisture in the system

d)any of the above

70) When starting a refrigeration system, always

a)vent the evaporator

b)bypass the condenser

c)vent the condenser

d)none of the above


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71) Solenoid valve controls the

a)amount of refrigerant entering the evaporator coils

b)amount of refrigerant going to the expansion valve

c)amount of refrigerant going to the compressor

d)pressure of refrigerant going to the evaporator coils.

72) The solenoid valve is controlled by

a)amount of liquid in the system

b)amount of gas in the system

c)temperature of the condenser

d)temperature of the icebox

73) A leaky dischg valve can be detected by

a)a drop in the icebox temperature

b)a dischg pressure lower than normal

c)a fluctuating high pressure guage

d)any of above

74) What will you do if the liquid start rising in the Surge Drum? (Direct cooling system)

a)Immediately reduce on the suction valve, and watch the Open more on the suction valve gauge.

b)Stop the compressor

c)It will never happen.

d)Open more on the suction valve.

75)Why is it so important to suck back as much freon liquid as possible from the evaporators, before

stopping the compressor?

a)To prevent low condensing pressure during start up.

b)To prevent low suction pressure during start up.

c)To prevent freezing of line.

d)To avoid liquid coming back to the compressor during start up.

76)To get the best possible efficiency from evaporators, the superheat should be regulated to:

a)-5 to -10 deg C


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b)+5 to 10 deg C

c)40 to 50 deg C

d)0 to 1 deg C

77)The thermoexpansion-valve does the following job

a)Regulating freon liquid flow to the evaporator.

b)Regulating the freon flow to condenser.

c)Regulating cooling water temperature.

d)Regulating the suction pressure.

78)If the reefer plant has air in the system , from where will you vent the air out?

a)From the evaporator.

b)From the compressor.

c)From the receivers bottom.

d)From the condenser.

Answers:

1c,2a,3d,4d,5d,6c,7d,8c,9a,10c,11d,12b,13b,14d,15c,16a,17c,18c,19c,20c,21b,22c,23a,24c,25a,26d,27b,

28d,29b,30a,31a,32a,33a,34b,35a,36c,37c,38c,39c,40b,41b,42b,43a,44c,45b,46b,47a,48a,49c,50d,51a,

52b,53c,54d,55a,56c,57b,58b,59c,60d,61d,62d,63a,64d,65b,66b,67d,68b,69c,70c,71b,72d,73d,74a,75d,

76b,77a,78d

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Maultiple Choice Questions for Refrigeration