問題一覧
1
Which method of charging should be used when working on an air conditioning system utilizing a fixed orifice
superheat method
2
Which revision listed below will not deplete the ozone layer
R410A
3
It's a coil of a gas valve is shorted out the heat anticipator will?
burnouts only if the thermostat is going for heat
4
Heating and cooling thermostats react to
sensible heat only
5
A duct measures 1 x 2 with air velocity of 300ft/min what is the CFM
600
6
When checking for resistance the meter use would be
ohm meter
7
In the diagram the refrigerant should be at what state at point D
low pressure, low temperature, liquid
8
Relays are not available in what?
triple throw models
9
The factor for calculating pressure drop in PSI per foot of rising vertical liquid lines for r22 at 100° f is
.56
10
The closing force of the TX valve is provided by
evaporator pressure
11
The amount of latent heat required to change one pound of water to 1 lb of ice
144 btu
12
When checking for current the meter use would be
ammeter
13
Which of the following terms best describes recycle
take refrigerant out of the air conditioning unit and place it and approved container put the refrigerant through an on-site oil separation distillation process and return the refrigerant to the system once prepared
14
If a single pole contactor on an air conditioning system with a trickle type crankcase heater is defective, and a double pole contactor is used as a replacement, how should the technician wire the new contactor?
both compressor wires to the load side of the contactor, in a jumper wire between the line and low terminals on one side of the contactor
15
If the water regulating valve on a water cool condensers restricted the head pressure will
increase
16
Latent heat is defined as
a change of state of a substance without a change of temperature
17
The vacuum pump is used too
remove oxygen and moisture from the air conditioning system
18
Which method of charging should be used when working on air conditioning system utilizing a TX valve
subcooling method
19
When installing air conditioning on an older standard furnace the technician will need to?
all the above, check for fan relay and install if one is not present, check a fan motor horsepower and consider installing larger motor and pulley, test all safety devices after altering any furnace wiring
20
Heat anticipators are
installed in series with the gas valve
21
The first law of thermodynamics states
heat cannot be created or destroyed
22
If the condenser fan motor is drawing high amperage, which of the following could be the blame?
low air flow through condenser
23
The contacts on a potential relay are?
normally closed
24
A zone damper that fails to open could cause
can cause low suction pressure for a heat pump in cooling mode
25
What condition could cause liquid refrigerant to load backup to the condenser
metering device offices to restrictive
26
But admit efficiency furnace with air conditioning installed if four wires are used for low voltage wiring between the furnace and the thermostat what must be done to ensure system works properly
jump RH and RC terminals in the thermostat
27
What is the maximum distance in electrical disconnect switch can be mounted from a residential air conditioning condensing unit
10 ft
28
Electrons flow because
they repel each other
29
A properly operating reversing valve will have?
two pipes that are hot two pipes that are cold
30
Residential ground Source heat pumps show The outdoor loop solution during
heating cycle
31
Motors briefly, during startup will
both a and b, cause a voltage drop, draw high amperage
32
If an air conditioning system has a non-bleed t type TXV valve installed, what component should also be installed on the compressor
hard start kit
33
Is it ever acceptable to install an evaporator in the return air duct of a furnace
yes
34
When checking for continuity the meter use would be
ohmmeter
35
Which of the following terms best describes recovery
take refrigerant out of the air conditioning unit and place it in an approved container
36
The sizes and length of liquid and suction line are important because?
both A and b
37
The cooling anticipator is?
non adjustable, energized during standby for cooling, and wired and parallel with the Mercury bulb
38
When capacitors are connected and parallel
the results thing capacitance is a sum of the individual capacitors
39
The contacts on a potential relay are?
normally closed
40
Evaporator pressure drop can be measured using
manometer
41
What is likely to happen if an r22 liquid line rises 120 ft, and the pressure at the condenser outlet is 200 PSIG, in the liquid line ambient is 85° Fahrenheit?
poor operation of the TX valve due to flash gas
42
A constant opening and closing functions of the TX valve is known as?
TX valve hunting
43
Which of the following is the correct method of checking high limit operation after fan center is installed
disable the blower, set the thermostat to call for heat, switch fan to on position
44
Which of the following is not acceptable for pressure testing air conditioning systems
oxygen
45
If an air conditioning system is being installed in a home in the new evaporator is unpackaged to discover that the end YouTube's are crushed what should you do
place evaporator with a new one
46
HFC refrigerant do not contain
Chlorine
47
Which of the following gases is the most dangerous to pressure test and air conditioning system wet
oxygen
48
If a meeting device is too restrictive?
all of the above: head pressure will increase, suction pressure will decrease, superheat will increase
49
If an r410a air conditioning system is being installed in a home in the new evaporator is unpackaged to discover that it is rated for r22, what should be done?
replace evaporator with r410a rated model
50
A reversing valve that has an internal leak will cause
decrease in the liquid temperature in the condenser
51
Resistance converts electricity into heat energy
true
52
On the diagram on the previous page the refrigerant should be in what state at point C
high pressure, medium temperature, liquid
53
A 35uf, 440v capacitor is faulty in a residential air conditioning unit the technician could replace a capacitor with which of the following choices placed in parallel with each other
20uf, 440v capacitor, 12.5uf 570v capacitor
54
To test a low pressure switch installed on a condensing unit you would
block air flow to the evaporator coil
55
An equalizing line on an external equalizing TX valve will connect the valve body to
evaporate outlet downstream of the sensing bulb
56
A clogged furnace air filter will cause
low suction line pressure
57
motors convert electricity to strong, moving, magnetic fields?
true
58
He probably operating reversing valve well
only change positions on a call for a cooling
59
For reading of 120 volts is obtained while measuring across a set of contacts that indicates?
contacts are open
60
A residential gas furnace typically uses a
15 amp, single pole breaker
61
On a combination fan and limit control the three tabs represent looking from left to right on the control
fan off, fan on, high limit
62
Proper amount of subcooling indicates
proper refrigerant charge, condenser functioning properly
63
The operating force of a reversing valve is?
system pressure
64
On the diagram on the previous page the refrigerant should be in what state at point b
high pressure, high temperature, vapor
65
The opening force of a TX valve is provided by
the sensing ball pressure
66
The amount of latent heat required to change 1 lb of water to 1 lb of steam is
970 BTU
67
What will be the approximate r22 liquid pressure at the metering device inlet if the liquid line rises 50 ft and the pressure at the condenser outlet is 200 PSIG assume 100° Fahrenheit
172 PSIG
68
Which of the following motors will have a start winding that is disconnected from the circuit after the motor has started
capacitor start induction run motor
69
A reading of 0 volts is obtained across an energized fuse which means
fuse is good
70
The most common type of compressor found in a residential air conditioning is
permanent split capacitor
71
An air conditioning system with a low evaporator load will?
open the low pressure switch
72
An a coil can contribute to furnace overheating
true
73
The type of soft copper used in residential air conditioning system is
type L
74
Hfc base refrigerants are responsible for?
greenhouse gas emissions
75
In an r22 system has a suction pressure of 15 PSIG and had pressure of 100 PSIG and the temperature of the suction line is 73° f and there is a small amount of frost at the end of the cap tubes what is the problem
major loss of refrigerant charge
76
Which of the following statements is true?
hot gas discharge lines have great heat content then the suction or liquid line
77
What is the RPM of an 8-in pulley if a 5-in drive pulley is spinning at 1360
850 RPM
78
When electrical loads are connected in parallel
both b and C
79
The suction line filter dryer must be installed
between the evaporator and the compressor
80
The standard reversing valve?
all of the above: needs at least 75 PSIG to charge position, needs solenoid coil energize to operate in cooling mode, is usually connected to the terminal in the C terminal
81
A flooded refrigerant condition in the evaporator could be caused by
low superheat setting
82
Volumetric efficiency increases when?
head pressure decreases
83
If an air conditioning system is not functioning in your call to a service equipment the following parameters are found 1. Compressor not operating 2. condenser fan not operating 3. 24 volts found across the contactor coil 4. 240 volts found on the line side of the contactor 5. 120 volts found across contacts 6. 1.2ohms reading across condenser fan motor windings 7. 1.5ohms reading across compressor R & C windings, 3ohms S and R compressor S and C windings and 4.5ohms across S and R windings 8. Compressor capacitor reads 33uf (35 is normal) 9. Condenser fan capacitor reads 4.8uf (5 is normal) What is the problem?
the contactor is defective
84
Proper use of a vacuum pump includes
all of the above
85
When the line set on an installed air conditioning system is longer than 50 ft and length the technician should
refer to the insulation instructions
86
A reversing valve
all of the buff
87
The technician must replace a 40uf, 440v capacitor,
38uf, 440v capacitor
88
Crankcase heater is used for
prevents liquid from migrating in the compressor
89
If a meeting device is too restrictive
all of the above: head pressure will increase, suction pressure will decrease, superheat will increase
90
Which of the following terms best to scratch reuse
take refrigerant out of the air conditioning unit and place it in an approved container and return the refrigerant to the system once repaired
91
When fresh air is introduced to a home for ventilation purposes
all of the above
92
What type of oil should be used for indoor blower motor
number 10 grade motor oil
93
If a 5uf capacitor and 15uf capacitors are placed in series with each other the resulting capacitance will be
3.75uf
94
Which of the following is a concern with r410a
it increases ground level ozone smog
95
Sensible heat is defined as
a change of temperature of a substance without change of state
96
When decommissioning an air conditioning unit the minimum standard and Ontario is to
recover
97
On the diagram on the previous page the refrigerant should be in what state at point a
low pressure, medium temperature, vapor
98
Upon discovering a refrigerant leak on an air conditioning system the technician should
recover refrigerant, repaire leak, pressure test with nitrogen, evacuate add proper charge of refrigerant, record ODP documentation
99
I reversing valves have?
two pipes connected to the compressor, one to the condenser, and one to the evaporator
100
A hydrometer is used to measure
specific gravity of a substance