HVACR Study Guide -2015 Flashcards
1
Q
The Evaporator in a refrigeration system
A
Is the component where refrigerant boils and absorbs heat
2
Q
The purpose of the compressor is to change
A
Low pressure, low temp vapor to a high pressure, high temp vapor
3
Q
A common refrigerant leak detection device is the
A
Halide torch
4
Q
Copper plating of compressor parts is
A
Caused by contaminants in the system
5
Q
If not properly installed, a hot gas muffler might trap
A
Oil
6
Q
Unit ventilators are usually equipped with outside air dampers to
A
Provide ventilation air during occupancy and comply with most local or state codes
7
Q
Face and bypass dampers should be adjusted to provide
A
Tight shut off to reduce the possibility of overcooling or overheating
8
Q
With belt driven equipment, alignment of the motor driven equipment pulleys
A
Is accomplished using a string or straight edge
9
Q
To assist consumer in making an informed choice when purchasing unitary air condition equipment, the efficiency of such units is expressed as Energy Efficiency Ratio(EER or SEER) the units of which are
A
BTUH/Watt
10
Q
Firestats located in the airstream of air handling units
A
Are required in both supply and return air streams
Should be the manual reset type
Should be non adjustable
11
Q
A sleeve bearing would typically be used in a motor that
A
Operates with a light load and where noise is a factor
12
Q
A bearing used on the bottom of a motor where the shaft is positioned vertically is called a
A
Thrust
13
Q
To produce electromagnetism, relative motion is required between a magnet field and a
A
Conductor
14
Q
Materials which do not allow there electrons to spin out of orbit easily are called
A
Insulators
15
Q
A battery is an example of a
A
Direct Current
16
Q
“Current flowing through a conductor in one direction for a split second, then in the opposite direction for a split second” would be a good definition of
A
Alternating Current
17
Q
If a pressure gauge reads 5 PSIG at sea level elevation, the corresponding absolute pressure is
A
19.7 PSIA
5psig + 14.7 psia
18
Q
Solar________ is the amount of solar thermal energy produced divided by the water heating energy demand of the building
A
Fractional
19
Q
The portion of the electromagnetic spectrum to which solar collectors respond _____ and near-infrared radiation
A
Visible Light
20
Q
During winter, _______
A
Daylight is shorter and the Northern hemisphere is angled away from the sun
21
Q
Unless equipped with OSHA or Canadian Standards Association(CSA) approved ground-fault circuit interrupters, portable electric light used in wet and or other conductive locations as, for example drums, tanks and vessels, shall be operated with ____ volts or less
A
12
22
Q
Receivers are usually required in systems having
A
Evaporative condensers
23
Q
An important feature of a refrigerant receiver, in the case where the liquid line to the evaporator comes out of the top of the receiver, is a
A
Dip Tube
24
Q
A pressure regulator is constructed so that a rise in _______steam pressure reduces off the inlet flow of supply steam
A
Downstream
25
A vaccum breaker is used to avoid which of the following
Negative gauge pressure
26
Lock out relays are used in air conditioning systems to
Prevent compressor short cycling
27
When measuring the winding resistance of a split phase compressor motor, the smallest value will measure between the
The run terminal and the common terminal
28
Cavitation in a pump pumping hot water
Makes a pump noisy
Is the result of water boiling into the steam
Is the result of insufficient NPSH
29
The amount of heat removed to lower the temperature of 15 lbs of water from 39 degrees to 48 degrees
135 BTU
Weight X BTU X Temp
15x1 (48-39) degrees
15 x 1 x 9 = 135 BTU
30
Atmospheric pressure at sea level is
14.7 psi
31
A dual element fuse has
A thermal cutout and normal fuse link
32
A single phase motor in which the run capacitor remains connected when the motor runs is called a
Permanent Split Capacitor Motor
33
The symbol below would be used to indicate a
Temperature actuated
34
The symbol below would be used to indicate a ______ switch.
Temperature-actuated
35
A refrigeration system has a hand-operated needle valve for the refrigerant
expansion device. If refrigeration load and suction pressure remain constant, a
decrease in condensing temperature will:
Result in reduced refrigerant flow unless the valve is opened.
Hand Valve
A simple type of expansion device which can provide an orifice of variable
size is a hand-operated valve. These were popular in ice plants that used
ammonia. Their use was acceptable because of various reasons including
the fact that there were always personnel available to adjust the valve,
and plant efficiency was not very critical. The disadvantage of
manually operated valves is their inability to automatically adjust
the flow rate
36
A full voltage starter has:
One contactor.
Reduced Voltage Starting
An “across-the-line” starter also known as a “full-voltage” starter, means
that when the contactor closes, the motor is immediately connected
directly to the power supply lines, and full voltage is at once impressed on
the motor. This is the least expensive way to start a three-phase motor.
However, this means that the motor will draw locked-rotor current until it
starts turning. Although this is not of any consequence with most motors,
the starting inrush current of large horsepower motors may cause the
power system voltage to dip, resulting in flickering of lights and other
objectionable effects on other electrical devices such as computers or
television apparatus.
37
The voltage rating of motor controller holding coils is:
Not necessarily the same as the motor supply voltage
An example of this would be in a high-voltage system (460 volts or higher)
where a lower control voltage would be desirable for safety reasons or
because some required control devices (such as thermostats, etc.) may not
be available in higher voltage ratings. Another example would be where
automatic control system is of low-voltage type, such as 24 volts. In such
cases, the holding coils are obtainable in the lower voltage ratings desired.
38
A lock-out relay should drop out when:
An overload relay opens
A lock-out relay is an electrically-operated control relay applied in such a
way that it can "lockout" a circuit, or cause it to remain de-energized when
once interrupted, as by some malfunction such as the tripping of a safety
device.
39
In starting up a chilled water system, the first piece of equipment to start should
be the:
Chilled water pump
The chilled-water pump is manually started by pushing the start button.
When the chilled-water pump is running, an auxiliary contact in its starter
completes the circuit. If in the "continuous" position, the condenser-water
pump will run whenever the chilled-water pump runs; if in the "automatic"
position, the condenser-water pump will run on calls for cooling. The
cooling-tower fan can be run at any time for test purposes by putting the
control switch in "manual" position. For normal operation in "automatic"
position, the cooling-tower fan can run on calls for cooling when the
condenser pump is in operation. The interlock is accomplished through an
auxiliary contact in the condenser-water pump starter which, upon closing,
feeds control power to terminals in the machine control panel. The
presence of control voltage at the terminals in the control panel also
permits the lubricating oil pump to start, and when oil pressure has built
up to normal, the compressor can start.
40
In a gas-fired warm air furnace, the furnace fan should:
Be controlled by furnace bonnet temperature
Bonnet temperature is sensed by the combination fan and limit control. As
the bonnet warms up, the operating control switch will close, and start the
fan. The main purpose of this control method is to keep the fan off until
warm air is available, so that cold air will not be blown into the heated
spaces.
41
A damper that must throttle air flow should have:
Opposed blade operation
Where throttling is required, a damper having opposed operation should be
used. In this type of damper, adjacent blades rotate in opposite directions,
resulting in a series of slots that become increasingly narrow as the
damper closes.
42
. A pressure regulator is constructed so that a rise in ____________ steam pressure
reduces off the inlet flow of supply steam.
Downstream
43
. A vacuum breaker is used to avoid which of the following:
Negative gauge pressure
A vacuum breaker is designed to prevent the pressure in the condensate
return from dropping too low. If system pressure drops below 15 in.Hg, the
breaker opens and lets air into the system. Since the pump draws from a
tank that is vented to the atmosphere (to allow air to escape), it will
typically see atmospheric pressure at the inlet and will be unaffected by
system pressure.
44
If the R value on a section of insulation is 8, what would the value be when
saturated with water?
0
The R value of the insulation when it is saturated with water has no
insulation value.
45
In a RTD (resistance type device), as temperature increases, resistance will:
Increase linearly
The three main classifications of temperature sensors are: RTD (resistive
temperature device), thermistor, and thermocouple.
• RTD’s generally increase resistance linearly as temperatures
rises (positive temperature coefficient).
• Thermistors devices generally decrease resistance as
temperature increases and are less linear then RTD’s.
• Thermocouples create a voltage proportional to temperature
change. They are constructed using two conductors made from
dissimilar metals that are connected at one end. This junction
point forms the tip of the temperature probe. Thermocouples
are highly versatile and can be adapted for use in many
applications.
46
Why is a surge suppressor used on a contactor coil?
To prevent damage to the control circuit
What is a Surge Protector?
A device that shields computer and other electronic devices from surges in
electrical power, or transient voltage that flow from the power supply.
Standard American voltage for home and office buildings is 120 volts.
Anything over this amount is considered transient and can damage
electronic devices that are plugged into an outlet. Even though power
surges are so brief that they are measured in nanoseconds, they can cause
considerable damage to electronic equipment.
47
A minimum evacuation level for an air conditioning system is:
500 microns.
A vacuum pump capable of removing the atmosphere down to a very low
vacuum is necessary. The vacuum pumps usually used in the refrigeration
field are manufactured with rotary compressors. The pumps that produce
the lowest vacuums are two-stage rotary vacuum pumps. These vacuum
pumps are capable of reducing the pressure in a leak-free vessel down to
0.1 micron. It is not practical to pull a vacuum this low in a field-installed
system because the refrigerant oil in the system will boil slightly and
create vapor. The usual vacuum required by manufacturers is
approximately 500 microns, although some may require a vacuum as
low as 250 microns.
48
One horsepower is the same as
746 watts
Power and Energy
Power means a rate of doing work. A common unit of mechanical power is
the horsepower. For example, a ten-horsepower motor can do mechanical
work, be it hoisting an elevator or turning the shaft of a compressor, at a
faster rate than can a one-horsepower motor. The unit of power in the
electrical circuit is the watt. It is equal to the voltage multiplied by the
current.
The formula is: Power = Voltage X Current or Watts = Volts X Amperes
A common unit of electrical power is the kilowatt which is 1000 watts.
Electrical power may be converted into mechanical power in an electric
motor, or it may simply be turned into heat in a resistance. Equivalents
are as follows:
One kilowatt (KW) = 1.34 horsepower
One watt = 3.413 Btu per hour
One horsepower is 746 watts
Energy is the amount of work done or explained. It is the product of the
rate of doing work multiplied by a length of time during which work is
done. The watt is the rate at which work is done electrically. The common
unit of electrical energy is the watt-hour, this being a measure of the
electrical energy consumed in one hour.
49
One watt is equivalent to
3.413 Btu
Power and Energy
Power means a rate of doing work. A common unit of mechanical power is
the horsepower. For example, a ten-horsepower motor can do mechanical
work, be it hoisting an elevator or turning the shaft of a compressor, at a
faster rate than can a one-horsepower motor. The unit of power in the
electrical circuit is the watt. It is equal to the voltage multiplied by the
current.
The formula is: Power = Voltage X Current or Watts = Volts X Amperes
A common unit of electrical power is the kilowatt which is 1000 watts.
Electrical power may be converted into mechanical power in an electric
motor, or it may simply be turned into heat in a resistance. Equivalents
are as follows:
One kilowatt (KW) = 1.34 horsepower
One watt = 3.413 Btu per hour
One horsepower is 746 watts
Energy is the amount of work done or explained. It is the product of the
rate of doing work multiplied by a length of time during which work is
done. The watt is the rate at which work is done electrically. The common
unit of electrical energy is the watt-hour, this being a measure of the
electrical energy consumed in one hour.
50
One kilowatt is equivalent to
1,000 watts
Power and Energy
Power means a rate of doing work. A common unit of mechanical power is
the horsepower. For example, a ten-horsepower motor can do mechanical
work, be it hoisting an elevator or turning the shaft of a compressor, at a
faster rate than can a one-horsepower motor. The unit of power in the
electrical circuit is the watt. It is equal to the voltage multiplied by the
current.
The formula is: Power = Voltage X Current or Watts = Volts X Amperes
A common unit of electrical power is the kilowatt which is 1000
watts.
51
The purpose of the external equalizer line used with a thermostatic expansion
valve is to compensate for:
Refrigerant friction through the evaporator
The External Equalizer
Superheat is abnormally high and serious loss of evaporator
capacity results if the evaporator has any appreciable pressure
drop. You might feel that you could compensate for the evaporator
pressure by simply adjusting the valve, but this will not give the
correct answer because the evaporator pressure drop varies. This
pressure drop is due to friction developed when the refrigerant
flows through the evaporator, just as friction is developed when a
fluid flows through an ordinary pipe. Pressure drop at partial loads
will be considerably less than at full load because of the smaller amount of
refrigerant flowing at the lighter loads.
The variable evaporator pressure drop is corrected for by sensing
evaporator pressure, not at the evaporator or valve inlet, but at the
evaporator outlet. This is done with a connecting tube called an external
equalizer line, and is connected to a suitable fitting on the expansion valve.
Such a fitting on an expansion valve should never be capped or plugged. If
the valve has an external equalizer connection, an external equalizer line
must be installed. The line should be connected to the suction line as close
as practical to the bulb; specially, there should be no elbows, or other
fittings which increase flow friction, between the equalizer line connection
and the bulb. The purpose of the external equalizer line is to be able to
sense suction pressure at the point where the bulb is located. In this
respect, you should consider that it is possible for some liquid refrigerant
to flow from the valve, through the equalizer line into the suction line.
Since any liquid will vaporize at that point, the resulting cooling effect
could influence the temperature sensed by the bulb. To avoid this, the
equalizer line should connect to the suction line at a point a little
downstream from the bulb.
52
Cleaning refrigerants to ARI 700 standards is called:
Reclaim
53
The unit of measure for the specific volume of air is:
FT 3/LB
An important concern of air conditioning systems is the quantity
of heat that a system can add or remove.
54
The amount of heat removed by evaporating one pound of water in an evaporative
cooling tower is approximately:
1000 btu
55
Which of the four lifting sling configurations shown below creates the greatest
amount of load strain on the sling
C
56
. The components marked “B” would be called the
Motor Contacts
57
Which of the following plans are typically NOT supplied in a complete set of
Building Plans?
As Builts
58
Common Relay configurations are
(SPST) Single Pole Single Throw
(DPDT) Double Pole Double Throw
59
The __________ is a device that allows the use of a low voltage power source to
operate a high Current load powered device.
Contactor
60
When troubleshooting a contactor in a system. One should check the contact
surfaces for:
Pitting
Wear due to arcing
61
Terminals “A” would be labeled
L1,L12,L3
62
The terminals marked “D” would be labeled
T1,T2,T3
63
Pushing P1 down energizes
M1 First
64
A (VFD) Variable Frequency Drive controls all but?
Motor Life
65
Three general categories of motor starter problems include all except:
Sizing
66
VFD’s can be tested when ___________ by means of __________ Measurements for
various sections.
Energized, Voltage
67
If the value of R1 is lowered, the current
Increases
68
If resistor R2 burns open, the current
Goes to zero
69
If the value of R3 is raised, the current
Decreases
70
All Screw compressors consist of 2 Rotors
One male and one female rotor
71
Capacity control for a helical screw compressor is done by?
The Slide valve
Motor Speed
72
If resistor R3 is shorted out the current
Increases
73
If the voltage goes up in a resistive circuit, the current
increases
74
If you find yourself at odds with a confrontational customer, you should
Keep your cool, learn as much as possible, but call your
| supervisor to report the incident
75
For applications where quiet operation and light axial load characteristics are
found, the type of bearing normally used is the:
Sleeve bearing
76
Sleeve bearings with the oil port lubrication system must be lubricated with the
proper oil because
Oil that is too thin will allow the shaft to run against the bearing surface.
Oil that is too thick will not run into the clearance between the shaft and the bearing surface.
The correct oil allows the tor shaft to float on a film of oil between the shaft and bearing surface.
77
Too much grease in grease lubricated ball bearing
Cause Overheating
78
. A ladder must extend above the edge of a roof by at least ______ ______.
3 Feet
79
The proper angle for a ladder is achieved when the distance of the ladder from the
building at the base is about __________ the working length (height) of the ladder.
1/4
80
. Air handling systems that employ economizers which permit outside air “free
cooling”
Are most economical when controlled by an enthalpy controller
81
When face and bypass dampers are used on systems with direct expansion cooling
coils:
Compressor capacity control is required
82
The rate of flow of electrons in a circuit is termed:
Amperage
83
“Pressure” differential in an electrical resistance is the:
Voltage
84
The unit used to measure electrical resistance is the:
Ohm
85
The four essential parts of the vapor compression cycle compressor, condenser,
evaporator and:
Expansion Device
86
How is an anticipator connected to a single contact cooling thermostat?
In parallel with contact
87
The process of removing moisture from air is called:
Dehumidification
88
Basic types of air supply outlets are:
Grilles
Three basic types of air supply outlets are:
1. Grilles
2. Slot diffuser outlets
3. Ceiling diffusers
89
With reference to copper tube, what is meant by the letters ACR?
Air conditioning and refrigeration tube
90
How is the heat anticipator wired in with heating contacts on a 24 volt space
thermostat?
Series
91
A piece of ice weighs 20 LBS and its specific heat is 0.49. It will require
__________ Btu to heat the piece of ice from 27 degrees to 31 degrees F.
39.2
```
Solution: Use for Formula:
Heat (Btu) = Weight (pounds) x Specific Heat (Btu per LB per degree F) x
Temperature Difference (degrees F)
= 20 x 0.49 x (31-27) degrees F
= 20 x 0.49 x 4
= 39.2 Btu
```
92
Given a rate of air flow of 2250 cfm in a duct having a cross-section 18 inches by
18 inches, the duct velocity should be ___________ fpm.
1000
V = 144 x cfm divided by a
= 144 x 2250 (324,000) divided by 18 x18 (324) = 1000 fpm
93
If a refrigerant sight glass shows bubbles, you know:
There is gas in the liquid
94
A liquid refrigerant receiver has two liquid level test cocks, one near the top of the
receiver and one near the bottom. If the system contains enough refrigerant,
when the lower cock is opened:
The test cock should discharge liquid refrigerant.
95
Desiccants are used in:
Driers
96
Only __________% of the direct radiation at the edge of Earth’s atmosphere
reaches the Earth’s surface.
51
97
Collectors should face as close as possible to ___________?
True South
98
_________ occurs in a Solar Thermal System when the heated transfer fluid
within the absorber piping rises within the collector and is replaced by cooler fluid
downstream.
Convection
99
A (n) ___________ system uses a Heat Transfer Fluid and heat exchanger to
transfer heat to the Domestic Hot Water without the use of mechanical means to
circulate the HTF.
Passive indirect
100
Self-pumping Systems are _________ systems.
Passive Direct
101
The vacuum pump used in vacuum steam heating systems that creates a
vacuum using high velocity water is the:
Jet Type Pump
102
Vacuum pumps used in vacuum steam heating systems can be destroyed if
they are made to pump:
by cavitation
&
Steam.
A common reason for pump failure is live steam entering the pump due to
failed steam traps. The cause of the pump failure must be corrected at the
same time the pump is repaired or replace. If bad steam traps allowed the
steam to reach the pump, the steam traps must be repaired or replaced or
the new pump will soon fail again
103
If a vacuum pump in a vacuum steam heating system burns out, a very
common cause is:
A failed steam trap.
104
Effective recovery of condensate reduces the following cost of making steam:
Fuel/energy costs associated with producing steam Other costs are also saved.
Boiler water make-up and sewage treatment.
Boiler water chemical treatment.
105
A symptom of a failed steam trap is:
A trap that is warmer than condensate temperature.
106
When entering a customer residential premises you should always
Place a clean pair of disposable covers over your shoes
107
If the technician is on a service call and notices another potential problem not
related to the current work order, what should the technician do?
Discuss what you have with the customer and your supervisor
| so that the customer can decide whether to authorize the additional repair
108
Which of the following is required part of the work order?
Form completed in legible hand writing
Complete list of materials used and amount of time spent on the job
109
Getting the customer to sign the work order should be
The last thing that you should do before leaving the job
110
Which of the following is a part of your responsibility relative to your work
crew?
Working safely on the worksite
111
The maximum desirable operating temperature of a ball bearing is
180 degrees F.
112
Shaft runout can be measured with
A dial Indicator
A Runout Gauge
113
The seal in a compressor is necessary to prevent
Refrigerant from leaking out the rotating shaft.
Oil from leaking out at the rotating shaft.
114
The mating seal surfaces on a sleeve type rotary bellows seal are:
Polished steel surfaces and a carbon ring
115
With belt driven equipment, alignment of the motor and driven equipment
pulleys
Is accomplished using a string or straight edge.
116
A lock and tag may only be removed by the employee that applied it, unless
the employee is absent from the workplace, then the lock or tag may be removed
by a qualified person designated by the employer to perform this task provided
that the employer ensures that ___________________________________.
The employee who applied the lock or tag is not available at the workplace.
The employee who applied the lock or tag is aware that
it has been removed before he or she resumes work at that workplace.
117
Section 608 of the Act prohibits you from knowingly venting ozone-depleting
compounds used as refrigerants into the atmosphere while maintaining,
servicing, repairing, or disposing of air-conditioning or refrigeration equipment
(appliances). The prohibition went into effect on ____________.
July 1, 1992
118
When working on a HCFC-22 appliance, or isolated component of such
appliance, normally containing 200 pounds or more of refrigerant and using
recovery or recycling equipment manufactured or imported on or after November
15, 1993, you are required to evacuate to a level of
10 In HG.
119
If a compressor burn has occurred, the refrigerant must be ____________
Recovered
Reclaimed
120
An advantage of the inverted bucket trap is that:
It also vents air and carbon dioxide continuously at steam
| pressure.
121
Flash steam is caused by:
Pipe friction
Reduced pressure
A vertical rise in a condensate line
122
The purpose of a drip leg in a steam line is to:
Let condensate escape by gravity from the fast-moving steam.
Store condensate until it can be discharged through the steam trap.
123
Inadequate trapping of steam mains often leads to:
Water hammer and damaging slugs of condensate.
124
Pressure in a vertical position condensate pipe will drop 1 psi for every ______
feet in elevation. This is an important factor, since boiling temperature drops as
pressure drops. When elevating condensate, this drop in pressure can cause flash
steam.
2.31
125
When using a listening device to test a steam trap, what would the technician
listen for that could indicate a problem.
High velocity sound.
126
If an inverted bucket steam trap is blowing live steam, what might the trouble
be?
The valve may have failed to seat because of wear or a piece of dirt or scale.
The trap may have lost its prime.
The bucket is stuck or has a hole in it
127
The ____________ drains the condensate from the steam header and returns it
to the boiler below the water line while preventing the boiler water from flowing
out of the boiler into the return line main.
Equalizing line
128
The ____________ is designed to protect boilers against the loss of water due to
leaks in the return line.
Hartford Loop
129
The control valve in a sub-atmospheric steam heating system is limited to
approximately ______ % change per minute.
3
The control valve is designed with a small percentage of change so there
are no radical changes in the pressure and steam temperature in the
system piping.
130
What is the most common cause of valve noise?
Valve piped incorrectly
131
When the discharge of one compressor is piped into the suction of another
compressor, it is called a:
Two stage system
132
What is the most common cause of valve noise?
Valve piped incorrectly
133
If too much refrigerant is being fed to the evaporator ____________.
The superheat will be low
134
The low pressure cap tube of an oil failure switch should be connected to the:
Compressor crankcase
135
When copper tubing is being brazed, nitrogen gas can be purged through the
system to prevent:
Oxidation inside the tubing
| Erection of Refrigerant Piping Systems Using Copper T
136
In an economizer, an enthalpy control regulates the use of outdoor air on the
basis of the air’s:
Humidity and temperature
137
When removing the gauge port plug from a compressor discharge service
valve, the valve should be:
Back seated
138
An acid test kit is used to test acidity of:
Oil
139
The TXV sensing bulb is mounted:
On the suction line as it leaves the evaporator
140
In an air cooled system with capacity control, compressor unloading will cause
the:
Suction pressure to rise and the discharge pressure to fall
141
A lamp has a source voltage of 110 volts and a current of 0.9 amperes. What is
the resistance of the lamp?
122.2
Solution: Ohms Law
R=E divided by I
110 divided by 0.9 = 122.2 ohms
142
The amount of heat removed to lower the temperature of 15 lbs. of water from
48 degrees F to 39 degrees F is:
135
```
Solution:
Heat = Weight (lbs.) x Specific Heat (btu/lb. per degree) F x Temperature
Change (degrees F)
= 15 x 1 (48-39) degrees f
= 15 x 1x 9
= 135 Btu
```
143
A belt-driven fan is to turn at 580 rpm. If the fan is driven by a 1740 rpm
motor and the motor has a pulley with a three-inch pitch diameter, the fan pulley
should have a pitch diameter of ___________ in.
9
Solution: RPM x D = rpm x d
580 x D = 1740 x 3 (5220)
D = 1740 x 3 (5220) divided by 580
= 9 in
144
Using a rule-of-thumb figure, approximately how much heat, in Btu/hr., must
be rejected by the condenser when the net refrigerating effect is 25 tons?
375,000
Solution:
“Rule-of-thumb” figure for condenser heat rejection is 15,000 Btu per ton of
net refrigeration effect.
25 tons x 15,000 Btu per ton = 375,000 Btu per hour
145
The heat transferred by calculating water can be expressed by the following
equation:
Btuh = 500 x gpm x delta T
A particular heat exchanger is supplied with circulating chilled water flowing at a
rate of 100 gpm. If heat is added to the water at a rate of 500,000 btuh when the
initial (entering) water temperature is 40 degrees F, at what temperature does
the water leave the heat exchanger?
50
```
Solution: Btuh = 500 x gpm x delta T
500,000 = 500 x 100 x delta T
Delta T = 500,000
500 x 100
Delta T = 10
Leaving temperature = 40 + delta t
Leaving temperature = 40 + 10
Leaving temperature = 50 degree F
```
146
What is the maximum safe amperage draw of the secondary winding of a 60
VA transformer output of 12 volts?
5
Solution: Divide VA by volts
60 divided 12 = 5 amps.
147
Theoretically, a pump can raise water by suction approximately ___________
feet vertically.
34
| Solution: Atmospheric press. (14.7 psi) = 33.95 (34) ft.
Weight of column of water 1’ high
.433 lb. per foot
148
The seal in a compressor is necessary to prevent
Refrigerant from leaking out at the rotating shaft
Oil from leaking out at the rotating shaft
149
Some codes require a manual reset device on a safety limit
So that the cause of the safety shutdown can be investigated prior to re-start.
150
A flame sensing relay strategy that takes advantage of the fact that hot gasses
in a flame become ionized and conduct electricity is called a
Flame Rod
151
When charging a system, the refrigerant cylinder pressure may drop too low
for further charging. Which of the following methods should not be used to
increase the pressure?
Heat the cylinder with a torch.
152
In a thermostatic expansion valve, three forces act on the diaphragm in the
power head, which is connected to the valve. Evaporator pressure acts to ______
the valve, spring pressure acts to ______ the valve and bulb pressure from the
bulb attached to the evaporator outlet acts to ______ the valve.
Close; close; open.
153
A stuffing box type of shaft seal on a centrifugal pump needs periodic
maintenance. If the seal is found to be leaking excessively, the technician should
Tighten the packing gland and/or replace the packing
154
Cavitation can destroy a centrifugal pump, is noisy and is caused by
Inlet pressure that is too low
155
Cavitation can destroy a centrifugal pump, is noisy and is caused by
Outlet pressure that is too high.
156
A vacuum breaker is installed between equipment and a steam trap to
Allow condensate to drain after the steam has been shut off.
157
Two types of thermal overload relays in common use today are
The bimetal relay and the melting alloy relay
158
When soldering, solder is drawn into the joint by
Capillary action.
159
The efficiency of an electric furnace is usually ______ percent
100
160
Defective rigging components and hardware should be
Destroyed
161
In order to reduce pressure to an acetylene pressure regulator, the adjusting
screw is turned
Counter-clockwise until the tension is of
162
Suction gas temperature leaving evaporator minus saturated suction
temperature equals
Superheat
163
Which of the following gases must never be used to pressurize or leak test a
refrigeration system?
Oxygen
164
For electric heat furnace what size should the flue pipe be?
No Flue
165
Defrost systems can be terminated by
Time
Pressure
Temperature
166
A refrigerant heat exchanger might cause:
The compressor to be overheated
167
The purpose of a suction line accumulator is to:
Trap liquid refrigerant
168
The proper location for an oil separator is near the:
Compressor
169
The two planes of alignment that must be considered when aligning a flexible
coupling are
Parallel and angular
170
How can you identify reverse operation with a scroll compressor?
The compressor will not compress.
The compressor will stop on motor overload.
171
When in doubt, what should be installed at the bottom of a suction line riser?
A p-trap
172
Condenser saturation temperature on air cooled condenser should be higher
than the ambient temperature by:
30 degrees F to 35 degrees F
173
The compression ratio in a system can be determined by:
Dividing discharge pressure absolute by suction pressure absolute
174
What is the “rule of thumb” in BTU’s per hour of heat rejection of a condenser?
15,000
175
Typical suction superheat at the evaporator outlet of an air conditioning
system is expected to be:
12 degrees F to 15 degrees F
176
The three pressures that operate the thermostatic expansion are bulb, spring
and evaporator
Bulb opens, spring closes, evaporator closes the valve
177
To add refrigerant to the system through the suction service valve, the valve
stem must be:
Mid Seated
178
How many Btu are there in 8 kW of electrical power?
27,304
179
An enthalpy controlled economizer system uses _______ for change from
mechanical cooling to economizer operation:
Outside temperature and humidity sensor.
180
For a voltage measurement the meter is connected:
In parallel to with load
181
To measure motor current:
Apply clamp-on amp meter around wire
182
Before you work on an electrical circuit (touching components)?
Check voltage with a good meter
183
When measuring voltage, the meter test leads are connected in _________ with
the component being tested.
Parallel
184
If the voltage is kept constant at 240 volts, and the resistance measures 40
ohms, the current flowing through the conductor is:
6 amps
| When the source of EMF provide
185
“VA” is the common term for:
Watts
186
. The device which operates similar to a fuse, but which can be reused, is a:
Circuit breaker
187
Fuses are sized by the __________ they can carry.
Amperage & Current
188
The 120V side of the transformer found on most heating system is referred to
as the:
Primary Winding
189
Relays are made up of a __________ and one or more __________.
Load & Switches
190
Terminal reheat systems:
Permit any zone to have year round heating or cooling
191
Variable volume systems:
Control space temperature by regulating the flow of air to each
zone
192
Volume limiting controls, also known as velocity controllers, used with
variable air volume boxes:
Maintain a stable discharge volume regardless of supply duct pressure
193
Air handling units of the multizone type:
Are able to supply each zone with heated or cooled air in all seasons
Are less economical to operate than VAV systems
Can have their hot deck temperature reset on coldest zone demand
194
To improve their operating economy, multizone air handlers should
Have their hot deck temperature reset by outside air temperature or on coldest zone demand
195
To improve their operating economy, multizone air handlers should
Be used with a variable capacity squirrel cage fan
196
Closed transition starting means:
The motor is never disconnected from the line during starting
197
Closed transition starting means:
The motor is never disconnected from the line during starting
198
For maximum safety of equipment, overload relays should be:
Manual reset type
199
For maximum safety of equipment, overload relays should be:
Manual reset type
200
Outdoor reset of hot water temperature for heating gives:
Hottest water during the coldest weather
201
The heating capacity of an air-to-air heat pump:
Decreases as outdoor air gets colder
202
The instrument used for finding humidity levels in the atmosphere is the:
Sling Psychrometer
203
Suction line filter-driers are usually equipped with gage connections so that
pressure drops can be determined. Why?
So that you can determine when to change the filter-drier.
204
The average house line pressure for Natural Gas is
7” W.C.
205
What air distribution system includes both a warm air duct and a cool air
duct, and utilizes mixing boxes near the zone to mix the cool air and warm air
streams and achieve the desired temperature while delivering air at a near
constant volume?
Dual duct.
206
Capacity control on a helical-rotary (screw) compressor is obtained using
A sliding valve.
207
Which of the following reduced voltage starters uses a switching arrangement
to connect the windings of three-phase motors in different configurations during
startup and normal operation?
Wye-delta starters.
208
One type of pressure sensing device uses a flattened metal tube, which is bent
into a part circle with one end fixed in place and connected to a system to be
measured. The other end of the tube is closed and free to move. An increase in
pressure tends to straighten the tube. The movement of the free end of the tube is
connected to a dial that reads pressure. This type of gage is called a
Bourdon tube.
209
With a change in temperature, a thermistor will change
Resistance.
210
Electricity results from the movement of tiny negatively charged particles
called
Electrons
211
___________ is the capacity of a material to store thermal energy for extended
periods.
Thermal Mass
212
The expansion tank in a steamback system is _________ a normally sized
expansion tank for a Solar Heating Water System.
Significantly larger than
213
Energy Efficient Ratio is a measure of the _____________.
Relative efficiency of a heating or cooling appliance
214
The ratio of the cooling output in Btu for the season, divided by the power
consumption in watts per hour for the season.
Seasonal energy efficiency ratio (SEER)
215
The heating Seasonal Performance Factor (HSPF):
Uses the total output of a system and the total electrical power
used by a system over an entire heating season
216
You are called to a job site to perform some maintenance work on a system
and after you are finished the customer approaches you and offers to pay you cash
directly to perform some additional work. In this situation it would be ok to?
Refuse the offer politely and if it happens again notify your
supervisor of the situation
217
What should the technician do in a situation where he is working on a
refrigeration system that operates a case that holds perishable food items, the
compressor has failed, it is 5:00 on a Monday evening, and will take a few
additional hours to repair the rack?
Request authorization from the customer to stay on the job until
it is finished that evening
218
The most important element(s) of non-verbal communication is (are)
Body language
219
The quality of customer service can be enhanced if the technician takes the
time to
Actively listen
220
An HVAC technician should always attempt to convey a professional image by
Clean and neat personal appearance
Clean and neat service vehicle (inside and outside)
Maintaining a clean and organized work site
221
If a technician determines he cannot keep a scheduled customer appointment
he should
Call the customer to keep them informed of your delay
222
Background checks are necessary to disclose employee history associated with
Criminal records
Credit reports
Drug testing
223
Which of the following would be a display of professionalism?
Work uniform with company logo
Being punctual
Use of good people skills
224
When completing a service call the last action taken is presenting the invoice
to the customer and obtaining a signature. Why it is important that all work
performed is accurately described on the invoice?
To reference details at a later date
To identify warranty parts or service
To provide service details in written communication
225
Service technicians must be thorough in order to prevent a breakdown in
communication that results in lost time (money). Which of the following is not
part of the required invoice information?
Original supplier of equipment
226
What measures can service technicians take to ensure that work orders are
complete?
Write legibly
Do not rush
Explain the work order to the customer and ask if they have any questions
227
To correct for soft foot:
Shim under the high foot with shim stock equal to a reading on
the indicator.
228
The two planes of alignment that must be considered when aligning a flexible
coupling are
Parallel and angular.
229
The first thing a service mechanic should do before performing service work on
refrigeration equipment is to:
Locate the disconnect switch.
230
EER labels are used on window units, unitary equipment and __________.
Heat pumps
231
EER labels are used on window units, unitary equipment and __________.
Garbage disposals
232
The Seasonal Energy Efficiency Ratio is used to measure the efficiency of
__________.
Central air conditioning
233
Which Government agency requires the display of the AFUE rating on
equipment?
Federal Trade Commission
234
It is not uncommon for condensing residential furnaces to approach AFUE
levels of _______%.
96
235
It is not uncommon for condensing residential furnaces to approach AFUE
levels of _______%.
96
236
AFUE stands for Annual Fuel _______ Efficiency
Utilization
237
Which Government agency requires the display of the AFUE rating on
equipment?
Federal Trade Commission
238
It is not uncommon for condensing residential furnaces to approach AFUE
levels of _______%.
96
239
___________ are used to control ventilation by monitoring the outdoor
temperature and humidity.
Economizers
240
An air filter with a MERV-6 rating or higher will reduce levels of small
particulates and improve indoor air quality. MERV stands for __________ value.
Minimum efficiency reporting
241
A solar Chimney used natural rising of warm air through a structure to
remove heat, this is true ________.
Passive cooling
242
There are two kinds of desiccant Solar Systems, they are ________ and
________.
Solid, liquid
243
To freeze one pound of water, ________Btu of latent heat must be removed.
144
244
The type of refrigerant that must be used now must be ______________.
HFC
245
All fittings and connections where refrigerants may be present should be
__________.
Brazed
246
The thermal storage system that uses small plastic balls for storage is called a
________.
Cell
247
The refrigerant line that connects the condenser to the metering device is
___________ line.
Liquid
248
The refrigerant line that connects the condenser to the metering device is
___________ line.
Liquid
249
The four main components of a refrigeration system are
Compressor, condenser, evaporator, & metering device
250
When an object is refrigerated:
Heat is removed from it.
251
A hand placed near a hot stove or fireplace is quickly heated by
Radiation
252
If you want to replace a defective capacitor but the only replacements you can
find do not have enough capacitance, you can increase their capacitance by:
Connecting two or more capacitors in parallel
253
The rotation of a three-phase motor can be reversed by interchanging:
Any two leads
254
A lamp source has a voltage of 110 volts and a current of 0.9 amperes. What is
the resistance of the lamp?
122.2
Ohms Law
R=E divided by 1
110 divided by 0.9 = 122.2 ohms
255
The difference between a contactor and a motor starter is:
Overload protection
256
When a three-phase motor single-phases, it:
Draws power from only one phase
257
The approach temperature for the evaporator is:
The difference in the refrigerant boiling temperature and the
leaving-water temperature
258
In a chiller, the refrigerant boils by ___________.
Absorbing heat from the water passing through it
259
If refrigerant condenses at a temperature of 105 degrees F and the water
leaves the condenser at a temperature of 95 degrees F, the ___________.
Condenser approach temperature will be 10 degrees
260
When water is introduced into the end of a chiller it is contained in:
Water boxes
261
When using a thermostatic expansion valve with a __________ charged
element, hunting can be considerably reduced.
Cross
262
A vacuum breaker is installed between equipment and a steam trap to:
Allow condensate to drain after the steam has been shut off.
263
The device which forms a water seal that prevents raw steam from entering
and damaging pressure gauges, vaporstats, pressuretrols, etc. is a (n):
Pigtail
264
The boiler return line is connected to the steam main by a (n):
Equalizing Line
265
The device which prevents a vacuum from forming in a low-pressure gravity
return steam heating system where automatic control is not used is a (n):
Air Vent
266
The device which prevents a vacuum from forming in a low-pressure gravity
return steam heating system where automatic control is not used is a (n):
Air Vent
267
The length of the pipe (drip connection) that is needed to overcome the
pressure drop in a one-pipe gravity return steam heating system and return
condensate to the boiler is:
28 Inches
268
In a one-pipe gravity return steam heating system, the main vent should be
installed:
In a tee at the end of the last steam carrying main
269
A thermostatic steam trap that fails in the closed position would cause a
heating unit to become:
waterlogged
270
If the float in a F&T trap failed and filled with water, the trap would:
Discharge steam continually
271
If used to drip the end of a steam main, the type of steam trap that would
require a cooling leg is a (n)
Thermostatic
272
In a two-pipe gravity return steam system, the device that prevents raw
steam from entering the piping is a:
Steam Trap
273
The pump motor on a condensate receiver is usually started by:
High condition in the receiver
274
The device that could be used to regulate the discharge pressure of a
condensate pump is a:
Plug Cock
275
The device used to actuate the vacuum pump in a vacuum steam heating
system when there is a loss of vacuum in the system return piping is the:
Vacuum Switch
276
The device which can be used to elevate condensate in a vacuum steam
heating system is a:
Lift Fitting
277
The device that is incorporated into a vacuum steam heating system to protect
the vacuum pump from creating too low (deep) a vacuum is a:
Vacuum breaker
278
In a vapor steam heating system, condensate is returned to the boiler by
means of a:
Boiler return trap (gravity)
279
Air is eliminated from a vapor system by a (n):
Air eliminator
280
The device that is used to maintain a pressure differential between the supply
and return piping in a sub-atmospheric steam heating system is
Differential controller
281
If the water flow to a water-cooled condenser is reduced, the temperature
difference across the condenser will:
Decrease
282
Basic types of heat pump, classified as to their heat source and the medium
being heated are:
Air-to-air
Water-to-air
Water-to-water
283
The external equalizer line on an expansion valve performs the following
function:
Compensates for any pressure drop in the evaporator coil
284
When the suction pipe from a direct expansion coil must rise to a level above
the coil outlet, what purpose is served by a trap placed in the line directly at the
coil outlet?
It assists the return of the oil to the compressor
285
If not properly installed, a hot-gas muffler might trap:
Oil
286
Double suction riser are used in refrigeration system when
Large fluctuations in system capacity will occur
287
Suction risers are typically reduced by one size over that of the main suction
run
To increase refrigerant velocity to aid in proper oil return
288
The liquid receiver is located between the?
Condenser and the expansion device
289
Which device is used in a refrigeration system to protect the compressor from
liquid slugs?
Suction accumulator
290
Which device is used to stop the flow of liquid or vapor in a refrigeration
system?
Solenoid valve
291
When soldering a copper pipe connection which of the following processes
allow for alloy to be drawn into the space between copper pipe and the fitting
connection?
Capillary action
292
Before proceeding to make any braze connection in a refrigeration system all
of the internal piping should be purged of atmosphere with
CO2
Nirogen
293
The purpose of the crankcase pressure regulator is to
Prevent a compressor overload condition.
294
The function of the evaporator pressure regulator is to:
Prevent a minimum pressure in the regulator
295
Oxygen hoses are generally what color?
Green
296
A type of copper tube joint is:
Soldered
Flared
Compression
297
If you were on a job and ran out of 5/8” O.D. fittings while installing 5/8” ACR
tube which of the following sizes of copper water tube fittings could be used?
1/2"
298
When soldering copper tube, after the tube and fitting are cleaned and fluxed,
they should be soldered:
As soon as possible
299
Condensate drain traps must be used on draw through evaporator coils in
order to prevent:
Water overflow
300
An excess of acetylene in an oxy-acetylene flame will give a/an:
Carburizing flame
301
In order to reduce pressure to an acetylene pressure regulator, the adjusting
screw is turned
Counter-clockwise until the tension is off
302
The wall thickness of Type K copper tube is:
Greater than that of Type L or Type M
303
Overheating a joint when brazing a wrought copper fitting causes
Oxidation and distortion of the joint
304
Which action is incorrect when working with an oxy-acetylene?
Use grease on the hose and regulator threading connections
305
When in doubt, what should be installed at the bottom of a suction line riser?
A p-trap
306
With reference to copper tube, what is meant by the letters ACR?
Air conditioning and refrigeration tube
307
Superheater tubes are protected from warping or burning out by:
Superheater tubes are protected from warping or burning out by:
308
To increase the life of furnace refractory, water-tube boilers are equipped
with:
waterwalls
309
When steam is superheated its:
Temperature is increased with no increase in pressure
310
Air is eliminated from a sub-atmospheric system by a (n):
Vacuum Pump
311
The device that controls the steam pressure on the supply side of a subatmospheric steam heating system is a:
Control valve
312
In order to return condensate to a boiler, the height of the water column
needed to overcome the pressure drop in a two-pipe gravity return system is:
28 inches for each pound of pressure the boiler is producing
313
The pump motor on a boiler feed pump is started when there is:
A low water condition in the boiler
314
Soot should be:
Removed from boiler tubes for better heat transfer
Soot deposits reduce heat transfer rates on the heating surfaces and
consequently reduce boiler efficiency, and increase metal surface
deterioration.
315
Thermostatic traps are opened and closed by a (n)
Flexible bellows
316
In a float and thermostatic trap the float rises to discharge:
Condensate
317
Condensate in steam lines could result in:
Water hammer
318
The type of traps normally used on steam radiators are:
Hermostatic traps
319
Which of the following is the common cause of back pressure in a condensate
return line?
Faulty steam trap
320
A vacuum breaker is used to avoid which of the following:
Negative gauge pressure
321
System powered variable air volume systems:
Operate by the system duct air pressure
322
The secondary water temperature of primary-secondary hydronic cooling
system, supplied to induction coils or chilled beams is regulated to:
Achieve maximum sensible cooling without latent cooling
| The water system has two portions, indicated as primary water circuit and
323
Achieve maximum sensible cooling without latent cooling
| The water system has two portions, indicated as primary water circuit and
Achieve maximum sensible cooling without latent cooling
| The water system has two portions, indicated as primary water circuit and
324
Achieve maximum sensible cooling without latent cooling
| The water system has two portions, indicated as primary water circuit and
Achieve maximum sensible cooling without latent cooling
| The water system has two portions, indicated as primary water circuit and
325
As a rule, the best general type of air diffuser to use in a variable air volume
system is the:
Slot diffuser
326
What is the maximum safe amperage draw of the secondary winding of a 40
VA transformer output of 24 volts?
1.67 amps.
327
The purpose of a hot-gas bypass valve is too:
Maintain evaporator load
328
If a refrigerant sight glass shows bubbles, you know:
There is gas in the liquid.
329
A hermetic motor should never be energized or tested with a megohmeter
when in a deep vacuum because
The dielectric strength of the motor’s insulation would be
| greatly reduced.
330
In order to protect a load, safety limit devices are most often wired
In series.
331
In a balanced three-phase system, the phase the voltage waveforms differ in
phase by:
120 degrees
332
Electrical pressure is measured in
Volts
333
A bellows is used:
In both pressure and temperature controllers
334
Roller bearings are normally used with:
Large motors operating with a heavy load.
335
The width of a drive belt is classified as:
Large or Small
Narrow or wide
336
An instrument often used to check the alignment of two shafts is the:
Dial Indicator
337
A loose-fitting belt on a belt-driven device will cause:
Worn pulley grooves
338
A flexible coupling between the drive and driven device:
Corrects minor misalignment.
339
If refrigerant is to be added to a system, the refrigerant cylinder is usually
connected to the
Center port of gauge manifold
340
On centrifugal pumps, if it is ever necessary to reduce pump flow, do so by
Throttling the discharge
341
Which of the following would happen if the vent port on a gas regulator is
plugged?
Outlet pressure will be reduced
342
Which of the following is NOT used to size gas regulators?
Type of ignition system
343
Which of the following is the common cause of back pressure in a condensate
return line?
Faulty steam trap
344
An evaporative cooling tower’s bleed rate is adjusted to maintain
The desired concentration of total dissolved solids
345
The run windings of a motor have ___________turns as compared to the start
windings
Fewer
346
On a typical split-phase electric motor the start winding circuit is de-energized
as it reaches approximately ____________ of its operating speed?
75%
347
What component wired in series with the start windings on a single-phase
motor will create greater starting torque
A capacitor
348
A three-phase motor does not have
Start Windings
A start capacitor
A Start Relay
349
A start component that is rated in microfarad would be a
Capacitor
350
What effect will a higher than rated supply voltage have on the current draw
of an electric motor?
It will be lower than it should be
351
With an electric motor running normally at full load the amperage reading
would be called?
Run-Load Amperage
352
What device would be discharged using a 20,000-ohm, 5 watt resistor?
Cpacitor
353
The run-load amperage on an electric motor is typically
1/5 that of a full-load amperage
354
What device is used to energize another load such as a contactor or motor
starter which in turn would start or stop a motor?
A pilot duty relay
355
A magnetic coil and electrical contacts are the primary components of this
electrical device?
A contactor
356
A magnetic coil, overload protector and electrical contactors are the primary
components of this electrical device
A motor starter
357
An electric motor that has an internal overload would have a?
A thermal device buried in the motor windings
358
What device could be used as external protection for a motor?
A line fuse
A circuit breaker
Magnetic overload
359
If a technician uses an ohm meter to check the windings of an electric motor
and records an infinite reading on the start windings this would indicate?
The start winding has an open somewhere
360
What type of motor would a technician switch any two legs on to reverse the
rotation of the motor?
Three Phase
361
Induction motors obtain good starting and running torque from
Start Windings
362
The primary application for shaded-pole motors would be
When low start torque is required
When low run torque is required
363
One of the most popular motors used in the HVAC industry with low starting
torque but improved running is the ___________ motor.
Capacitor-run
