問題一覧
1
Which of the following could be used to check a leak in an ammonia system?
Litmus paper and Sulfur Stick
2
Ammonia leaks in the condenser can be detected by:
Applying litmus paper to the circulating discharge
3
23. The solenoid valve is located between the...
scale trap and the thermal expansion valve
4
The oil separator is located between the...
compressor and condenser
5
Which of the following is the most appropriate definition of Latent heat?
heat added to change the state of a substance
6
The charging valve is located between the...
king valve and the expansion valve
7
Excess frost on the evaporator coils...
reduces efficiency of the plant
8
The dehydrator is used
to remove moisture from the system and adding refrigerant to the system
9
In an ammonia system the oil gauge must be kept.
closed except when checking oil level
10
Which of the following must be considered when adding or removing oil from a refrigerator unit?
all of the above
11
The discharge pressure of the compressor should be...
the pressure which corresponds to a temperature from 6°F to 15°F higher than the condenser discharge.
12
A leaky suction valve can usually be detected by...
any of the above
13
Thermal expansion valves are usually of the:
diaphragm and bellows type
14
When purging an ammonia condenser into a bucket of water, one can tell when the air is out and ammonia starts to come through by the:
change of bubbling sound of air to the crackling sound of ammonia
15
The solenoid valve is:
a temperature-controlled stop valve
16
If no gaskets are used in the piping joints of a Freon system, the joints must be...
ground joints
17
The dehydrator is located between the...
receiver and the expansion valve
18
The scale trap is located between the:
king (liquid) valve and expansion valve
19
A sulfur stick burning in the presence of ammonia will give off a...
dense white smoke
20
A device used to keep moisture from passing through the system is called:
dehydrator
21
When the evaporator coils are located in the icebox, the system is known as:
direct system
22
The bulb for the thermal expansion valve is located
near the evaporator coil outlet
23
A double-pipe condenser has .
a small pipe inside a larger pipe, the cooling water passing through the small pipe and the refrigerant through the large pipe.
24
The thermal expansion valve is located between the...
solenoid valve and the evaporator coils
25
The purpose of the scale trap is to:
remove dirt, scale and metal chips from the refrigerant
26
The crossover connection in an ammonia system can be used to...
hot-gas defrost
27
Valves and piping in an ammonia system are made of:
iron
28
The temperature bulb of the solenoid valve is attached to the...
wall of the icebox
29
The oil separator (trap) is located between the
compressor discharge valve and the condenser
30
If a Freon -12 compressor trip out on "cut-out, the solenoid valve closes by which of the following?
an electrical release
31
How is a one-ton plant described?
remove the heat required to melt one ton of ice in 24 hours
32
How is an ammonia system purged so that operator not be overcome by the fumes?
Into a bucket of water
33
Obstruction of the expansion valve is usually caused by.
any of the above
34
A bull’s eye in a full liquid line will appear .
clear
35
Which of the following is another name for the liquid valve?
king valve
36
The relief valve is located on the...
discharge side of the compressor
37
The relief valve on an ammonia machine is located:
on the discharge pipe from the condenser and compressor
38
The cooling water regulator is automatically actuated by which of the following?
the discharge pressure of the refrigerant
39
Zinc rods are found in the...
salt-water side of condenser
40
If there is too much lube oil in the system, what must be done?
remove same at once
41
The temperature bulb of the thermo-expansion valve is attached to which of the following?
evaporator coil outlet
42
When removing reusable refrigerant from a system, the line to the storage drum must...
contain a strainer-dryer
43
Too low suction pressure could be caused by...
any of the above
44
The compressor discharge becomes frosted, the probable cause would be...
refrigerant flooding back
45
A device for holding open the suction valve and drawing gas from the suction manifold and returning it to the suction line without compressing it is called...
cylinder unloader
46
Large leaks in a Freon system cannot always be detected with a halide torch because it changes color with the slightest amount of Freon present. A large leak can be detected easier by applying
A soapsuds solution together, mixed with a little glycerine to hold the solution together, and watch for bubbles.
47
The purpose of relief valves on refrigeration machines is to...
prevent excessive pressure in case of stoppage of the discharge side of the system.
48
The relief valve on a CO₂ machine is located...
on the discharge pipe between the compressor and the discharge valve
49
The charging connection in a refrigerating system is located
between the king valve and the solenoid valve
50
What do you call a system in which the evaporator coils are located in a brine solution and the brine is pumped through the icebox?
an indirect system
51
If there were a 15°F to 20 F temperature differential between the temperature corresponding to the pressure at the compressor discharge and the temperature at the condenser outlet, it would probably indicate the need for...
purging the system
52
The elements of a thermostat switch are usually of the
bimetal type
53
Which of the following is also known as the “hidden heat” in refrigeration work?
latent heat
54
All refrigerator compressor valves are opened and closed by
springs
55
Where is the excess refrigerant removed?
charging side of the system
56
The expansion valve is located between the...
receiver and evaporator
57
What will happen to the capacity if the superheat is increased on the suction side?
decreases
58
What is the use of the suction pressure regulating valve?
maintains the back pressure in the
59
What usually happens if the specific gravity of the brine is too low?
the brine will freeze
60
Which of the following is important for evaporator coils?
it should have air completely surrounding them
61
A compressor capacity reduction device reduces compressor capacity...
as the refrigerant load dictates
62
40. When there is a Freon leak, the halide torch will burn:
green
63
The thickness of the head gasket is important because it may cause...
all of the above
64
An ammonia leak will turn litmus paper...
blue
65
When checking zinc plates in a condenser, one should:
clean the plates and renew worn out ones
66
Which of the following gasket materials should be used on a Freon system?
Asbestos and Metallic
67
A double trunk piston is used to
all of the above
68
A double-trunk piston is used to
all of the above
69
The solenoid valve can be typed as a...
magnetic stop valve
70
Before securing a compressor to do maintenance work on it, be sure to.
D,B, and C
71
Many pressure gauges on a Freon system have two dials or graduations on one gauge. The two dials represents...
pressure and temperature
72
Which do you think is very important in adjusting compressor "V" belts?
allow about ½" slack
73
The purge valve is located:
in the highest part of the system
74
If the expansion valve capillary tube is pinched, which of the following must be replaced?
all of the above (called the power element unit)
75
How do you call the process of changing a solid to a liquid?
fusion