77)
77)
Compressor cylinder unloading reduces the capacity of a reciprocating compressor by:
A)
Flooding the unloaded cylinders with oil.
B)
Disconnecting the pistons in the unloaded cylinders.
C)
Blocking off the discharge port in the unloaded heads.
D)
Making the valves in the head inoperative.
Answer:
D
Explanation:
78)
78)
One technique for improving efficiency and comfort through compressor selection is to select a:
A)
Compressor with a capacity equal to the minimum anticipated refrigeration load.
B)
Compressor that is designed for a colder evaporator temperature to achieve lower
evaporator pressure and increased efficiency.
C)
Compressor with capacity control to match the compressor capacity with the refrigeration
load.
D)
Compressor with 25% greater capacity than the maximum anticipated refrigeration load.
Answer:
C
Explanation:
79)
79)
The shaft seal on an open compressor is more complicated than the gaskets and seals on other
parts of the compressor because:
A)
It must seal in a vacuum.
B)
It must seal against a higher pressure.
C)
It must seal a shaft that is turning.
D)
It is subjected to both refrigerant and oil while other seals and gaskets are not.
Answer:
C
Explanation:
80)
80)
Refrigeration needs on trucks, tractor trailers, and shipping containers are met by:
A)
Centrifugal compressors.
B)
Scroll compressors.
C)
Open–drive compressors.
D)
Screw compressors.
Answer:
C
Explanation:
21
81)
81)
An advantage of open–drive compressors is that:
A)
The motor and compressor can be replaced separately.
B)
They require no type of regular maintenance.
C)
They are smaller and more compact than hermetic compressors.
D)
They are generally less expensive than comparable semihermetic compressors.
Answer:
A
Explanation:
82)
82)
Rotary compressors are commonly used in:
A)
Chillers.
B)
Commercial refrigeration systems.
C)
Large central split systems.
D)
Window units.
Answer:
D
Explanation:
83)
83)
All refrigeration compressors are designed to pump:
A)
Only liquid.
B)
Mostly liquid with small quantities of vapor.
C)
Only vapor.
D)
Mostly vapor plus small quantities of liquid.
Answer:
C
Explanation:
84)
84)
The match of the motor and compressor inside a hermetic compressor:
A)
Is specific for the application of the compressor.
B)
Is typically 1 hp per ton for nearly all applications.
C)
Is made in the field by the installing technician.
D)
Is generally not critical, allowing a single compressor to cover a wide range of applications.
Answer:
A
Explanation:
22
85)
85)
How can semihermetic compressors be characterized?
A)
They have a welded shell, which holds both the compressor and motor.
B)
They have a bolted housing that encloses both the compressor and motor.
C)
They have a welded shell with a shaft that connects to an external motor.
D)
They have a shaft that connects to an external motor.
Answer:
B
Explanation:
86)
86)
The space left between the piston and the valve plate of a reciprocating compressor when the
piston is at the top of the cylinder is called:
A)
The bore.
B)
The mechanical allowance.
C)
The clearance volume.
D)
The stroke.
Answer:
C
Explanation:
87)
87)
How does a two–step scroll compressor achieve capacity reduction?
A)
An internal rotating plate opens and closes two drilled ports in the scroll.
B)
The orbiting scroll only completes half–orbits in low–capacity operation.
C)
Only one scroll is used during low–capacity operation, while both are used for full–capacity
operation.
D)
The orbiting scroll turns clockwise for reduced capacity and counterclockwise for full
capacity.
Answer:
A
Explanation:
23
88)
88)
Which compressor has a piston that is driven up and down in the cylinder by a connecting rod
and crankshaft?
A)
A reciprocating compressor
B)
A hermetic compressor
C)
An open drive compressor
D)
A nonpositive–displacement compressor
Answer:
A
Explanation:
89)
89)
A compressor that compresses gas between a fixed spiral and an orbiting spiral is a:
A)
Screw compressor.
B)
Scroll compressor.
C)
Rotary compressor.
D)
Centrifugal compressor.
Answer:
B
Explanation:
90)
90)
Which compressor type draws refrigerant gas in through the inlet port into voids created by
turning rotors?
A)
A screw compressor
B)
A reciprocating compressor
C)
A rotary compressor
D)
A scroll compressor
Answer:
A
Explanation:
91)
91)
What is the lowest percentage of full capacity that a digital scroll can be safely operated for
extended periods?
A)
The compressor can be operated at 0% by simply leaving the unloading solenoid energized.
B)
The minimum capacity is 10% to ensure that the compressor gets proper lubrication.
C)
The digital scroll compressor can only operate at full capacity.
D)
The digital scroll compressor cannot be operated below 50% capacity.
Answer:
B
Explanation:
24
92)
92)
How does a reciprocating compressor operate?
A)
In a reciprocating compressor, the piston remains stationary in the cylinder between the
connecting rod and crankshaft.
B)
In a reciprocating compressor, the piston is driven up and down in the cylinder by the
connecting rod and crankshaft.
C)
In a reciprocating compressor, the piston is moved side to side in a cylinder by the
connecting rod and crankshaft.
D)
In a reciprocating compressor, the piston is moved in every direction around the cylinder by
the connecting rod and crankshaft.
Answer:
B
Explanation:
93)
93)
A compressor that uses a large off–center rotating shaft and multiple blades that follow the
cylinder walls as the shaft rotates is a:
A)
Reciprocating compressor.
B)
Rotary blade rotary compressor.
C)
Rotary screw compressor.
D)
Stationary blade rotary compressor.
Answer:
B
Explanation:
94)
94)
The major types of compressors listed by mechanical design are:
A)
Air cooled, water cooled, and refrigerant cooled.
B)
Reciprocating, rotary, scroll, screw, and centrifugal.
C)
Hermetic, semihermetic, and open.
D)
Forward curved, backward curved, radial, in–line.
Answer:
B
Explanation:
25
95)
95)
Three different design screw compressors are:
A)
Single screw with gate rotors, dual screw, and triple screw.
B)
Micro screw for small appliances, standard screw for 25–ton applications, and mega screw
for industrial applications.
C)
Open screw, semihermetic screw, and variable screw.
D)
Single screw, compound screw, and compound–complex screw.
Answer:
A
Explanation:
96)
96)
What type of compressors contain the compressor and motor together inside a welded steel
housing?
A)
Semihermetic compressors
B)
Open compressors
C)
Reciprocating
D)
Hermetic compressors
Answer:
D
Explanation:
97)
97)
The advantage of compliance in a scroll compressor is that:
A)
The compressor is very flexible in its application.
B)
The orbiting scroll can separate and unload to pass a small liquid slug.
C)
The top of the compressor can be rotated 180° to comply with many refrigerant piping
arrangements.
D)
The compressor complies with all national compressor standards.
Answer:
B
Explanation:
98)
98)
A common application for centrifugal compressors is:
A)
Commercial water chilling systems.
B)
Residential split systems.
C)
Small appliances.
D)
Low–temperature, commercial refrigeration.
Answer:
A
Explanation:
26
99)
99)
In which system does less refrigerant enter the cylinder for each compression cycle, requiring
more horsepower for each BTU of cooling?
A)
A low–evaporator–temperature system
B)
A low–condenser–temperature system
C)
A high–evaporator–temperature system
D)
A high–condenser–temperature system
Answer:
A
Explanation:
100)
100)
Which of the following compressors is NOT considered a positive–displacement compressor?
A)
Centrifugal
B)
Screw
C)
Reciprocating
D)
Rotary
Answer:
A
Explanation:
101)
101)
What opens and closes the valves in a reciprocating compressor?
A)
Hydraulic valve lifters
B)
The piston pushes them open.
C)
Pressure difference across the valves
D)
A cam shaft
Answer:
C
Explanation:
102)
102)
The function of the compressor in the refrigeration cycle is to:
A)
Lower the pressure and temperature of the refrigerant.
B)
Regulate the refrigerant flow.
C)
Raise the pressure and temperature of the refrigerant.
D)
Filter the refrigerant.
Answer:
C
Explanation:
27
103)
103)
How can tube–in–tube condensers become contaminated?
A)
Cross–contamination can occur if the pressure increases.
B)
Cross–contamination can occur if the inside tube leaks.
C)
Cross–contamination can occur if the outside tube leaks.
D)
Cross–contamination can occur if the pressure drops.
Answer:
B
Explanation:
104)
104)
Fan cycling, fan speed control, damper control, and condenser flooding are different types of:
A)
Energy efficiency improvements.
B)
System capacity control.
C)
Protection against excessively high condenser pressures.
D)
Condenser low ambient controls.
Answer:
D
Explanation:
105)
105)
How can water–tubing fouling be prevented in tube–and–shell water–cooled condenser systems?
A)
Through annual draining and replacement of the water in the condenser and annual
chemical treatment of the water
B)
Through a monthly external scrubbing with bleach
C)
Through annual chemical treatment of the water
D)
Through annual draining of the water, removing access plates, and running brushes
through the water tubes
Answer:
D
Explanation:
106)
106)
Which type of condenser uses a fan to push air across the condenser?
A)
An induced–draft air–cooled condenser
B)
A packaged air–cooled condenser
C)
A natural–draft air–cooled condenser
D)
A forced–draft air–cooled condenser
Answer:
D
Explanation:
28
107)
107)
The fins on finned tube coils increase heat transfer by:
A)
Increasing the laminar air flow through the coil.
B)
Increasing the surface area exposed to the air.
C)
Increasing the laminar refrigerant flow through the coil.
D)
Directing the air smoothly across the coil.
Answer:
B
Explanation:
108)
108)
Cooling towers in which the water circulating in the tower is separate from the water circulating
through the condenser are called:
A)
Evaporative cooling towers.
B)
Open–loop cooling towers.
C)
Closed–loop cooling towers.
D)
Regenerative cooling towers.
Answer:
C
Explanation:
109)
109)
In a water–cooled condenser, what do an increase in head pressure and a decrease in temperature
difference across the condenser indicate?
A)
Scaling on tubing
B)
Undersized condenser
C)
Low–pH water
D)
Low water flow
Answer:
A
Explanation:
110)
110)
Water conditions that must be monitored to keep a cooling tower system working properly
include:
A)
Isothermal capacity, density, and opacity.
B)
pH, mineral content, and biological growth.
C)
Ambient temperature and relative humidity.
D)
Incoming water pressure, sump water level, and sump water pump inlet pressure.
Answer:
B
Explanation:
29
111)
111)
The three basic types of condensers used with HVACR systems are:
A)
External, internal, and cross–charged.
B)
Standard, metric, and transitional.
C)
Condensing, noncondensing, and static.
D)
Air cooled, water cooled, and evaporative.
Answer:
D
Explanation:
112)
112)
In a water–cooled condenser, what do an increase in head pressure and an increase in
temperature difference across the condenser indicate?
A)
Low water flow
B)
Scaling on tubing
C)
Biological fouling
D)
Fouled condenser
Answer:
A
Explanation:
113)
113)
If the refrigerant is recovered improperly from a water–cooled condenser:
A)
All the water may drain out of the condenser.
B)
The water may freeze.
C)
The water may boil.
D)
The oil dissolved in the refrigerant may crystallize.
Answer:
B
Explanation:
114)
114)
An evaporative condenser:
A)
Works by evaporating water to cool the condenser coil.
B)
Cools air through the evaporation of refrigerant inside the condenser.
C)
Works by evaporating refrigerant to cool the condenser coil.
D)
Is really just another name for evaporator.
Answer:
A
Explanation:
30
115)
115)
Why are biocides added to cooling–tower water?
A)
To increase biofilm
B)
To decrease the pH
C)
To increase the pH
D)
To reduce biofilm
Answer:
D
Explanation:
116)
116)
Compared to other coil constructions, microchannel coils:
A)
Are much larger for the same capacity.
B)
Have a larger internal volume.
C)
Are much smaller for the same capacity.
D)
Are much more expensive.
Answer:
C
Explanation:
117)
117)
The first check to make whenever working on a water–cooled system is:
A)
System operating pressures.
B)
Compressor amp draw.
C)
Condenser water flow.
D)
Outdoor ambient wet bulb temperature.
Answer:
C
Explanation:
118)
118)
As it passes through the condenser, the refrigerant is:
A)
Condensed from a gas to a liquid, and then superheated.
B)
Desuperheated, condensed from a gas to a liquid, and subcooled.
C)
Superheated, condensed from a liquid to a vapor, and then subcooled.
D)
Condensed from a gas to a liquid, and then subcooled.
Answer:
B
Explanation:
31
119)
119)
The purpose of the condenser in a refrigeration system is to:
A)
Increase the pressure and temperature of the refrigerant.
B)
Reject heat from the refrigerant.
C)
Reject heat from the condensing medium.
D)
Absorb heat into the refrigerant.
Answer:
B
Explanation:
120)
120)
How many BTUs does each pound of water evaporating remove?
A)
1070
B)
870
C)
970
D)
1170
Answer:
C
Explanation:
121)
121)
How much heat is rejected through condensation?
A)
80%
B)
60%
C)
100%
D)
40%
Answer:
A
Explanation:
122)
122)
Subcooling the liquid refrigerant increases system efficiency by:
A)
Ensuring a solid stream of liquid to the metering device.
B)
Ensuring no liquid enters the compressor.
C)
Adding refrigerant to the system that has already been cooled.
D)
Cooling off the compressor motor.
Answer:
A
Explanation:
32
123)
123)
What is the primary advantage of a remote air–cooled condenser on an ice machine?
A)
The compressor noise is reduced.
B)
Installation is easier.
C)
The heat generated by the ice machine is expelled outside instead of into the kitchen.
D)
The ice freezes faster.
Answer:
C
Explanation:
124)
124)
The main cause of high condensing temperature and pressure in air–cooled condensers is:
A)
Excessive airflow over the condenser.
B)
Operating the condenser at low ambient temperatures without head pressure controls.
C)
Dirty condensers.
D)
Refrigerant undercharge.
Answer:
C
Explanation:
125)
125)
What is the purpose of a cooling tower?
A)
It cools the water flowing through it by evaporating a small portion of the water.
B)
It cools the refrigerant by evaporating a small portion of the refrigerant to the air.
C)
It cools the water flowing through it by passing it over ice that is made during off peak
hours.
D)
It cools the water flowing through it by using a separate compression refrigeration system.
Answer:
A
Explanation:
33
126)
126)
Which type of condenser requires the most maintenance?
A)
The maintenance requirements for air–cooled condensers and water–cooled condensers are
comparable.
B)
Condensers do not require maintenance.
C)
Water–cooled condensers
D)
Air–cooled condensers
Answer:
C
Explanation:
127)
127)
Tube–in–tube, shell–and–coil, and shell–and–tube are all different types of:
A)
Evaporative condensers.
B)
Air–cooled condensers.
C)
Natural–draft condensers.
D)
Water–cooled condensers.
Answer:
D
Explanation:
128)
128)
What is the purpose of low ambient controls for air–cooled condensers?
A)
To control the ambient temperature
B)
To increase the fan speed to compensate for low barometric pressure
C)
To maintain a minimum head pressure, even at lower–than–normal operating conditions
D)
To maintain a maximum head pressure, even at lower–than–normal operating conditions
Answer:
C
Explanation:
129)
129)
The primary cause of high condensing temperatures in water–cooled condensers is:
A)
Restricted metering devices.
B)
Excessive water flow.
C)
Scaled and fouled condenser surfaces.
D)
Oversized condenser water circulating pumps.
Answer:
C
Explanation:
34
130)
130)
How much would system capacity be increased by subcooling the liquid refrigerant leaving the
condenser an extra 12°F?
A)
12°F × 5%/°F = 60% increased capacity
B)
12°F × 0.5%/°F = 6% increased capacity
C)
12°F × 1%/°F = 12% increased capacity
D)
Subcooling does not increase system capacity.
Answer:
B
Explanation:
131)
131)
If the refrigerant condensing saturation temperature is 100°F at the start of the process, what
would the entering water temperature be?
A)
80°F
B)
50°F
C)
110°F
D)
20°F
Answer:
A
Explanation:
132)
132)
What is the best pH level to maintain in a water tower?
A)
Between 6.5 and 9
B)
Lower than 6
C)
The pH of the water has very little effect on the operation of the cooling tower.
D)
Higher than 9
Answer:
A
Explanation:
133)
133)
What is the primary difference between air–cooled condensers on lower–efficiency systems and
those on high–efficiency systems?
A)
The coil size is increased to increase the heat–transfer area.
B)
The number of fins per inch is reduced to reduce the restriction to airflow.
C)
The condenser coils are made from steel instead of copper or aluminum.
D)
The coil size is decreased to raise the head pressure and increase the temperature difference.
Answer:
A
Explanation:
35
134)
134)
Technicians should be careful when brazing lines to evaporator coils that have preinstalled
thermostatic expansion valves because the heat from brazing the lines:
A)
Can weld the sensing bulb to the suction line.
B)
Can catch the refrigerant on fire.
C)
Alters the chemical makeup of the bulb charge and changes its physical properties.
D)
Can overheat the TEV bulb and destroy the valve.
Answer:
D
Explanation:
135)
135)
A restricted inlet screen on a TEV can cause:
A)
Low suction pressure, high superheat, and high subcooling.
B)
High suction pressure, low superheat, and low subcooling.
C)
High suction pressure, high superheat, and low subcooling.
D)
Low suction pressure, low superheat, and low subcooling.
Answer:
A
Explanation:
136)
136)
Which metering device used on flooded evaporators opens when more refrigerant
condenses,enabling the refrigerant to flow into the evaporator?
A)
High–side float
B)
Electronic expansion valve
C)
Low–side float
D)
Automatic expansion valve
Answer:
A
Explanation:
137)
137)
Which of the following metering devices can respond to changes in system conditions?
A)
Fixed restriction
B)
Orifice
C)
Capillary tube
D)
Thermostatic expansion valve
Answer:
D
Explanation:
36
138)
138)
The most common application of the high–side float controls is:
A)
Residential air conditioners.
B)
Window units.
C)
Freezers.
D)
Large chillers.
Answer:
D
Explanation:
139)
139)
What advantages do orifice–type metering devices have over capillary tubes?
A)
They adjust to changing operating conditions.
B)
They are more efficient.
C)
They are easy to change.
D)
They equalize during the off cycle.
Answer:
C
Explanation:
140)
140)
The operation of a thermostatic expansion valve can best be described as:
A)
Bulb pressure + evaporator pressure = spring pressure.
B)
Spring pressure = bulb pressure + evaporator pressure.
C)
Evaporator pressure = evaporator pressure + bulb pressure.
D)
Bulb pressure = evaporator pressure + spring pressure.
Answer:
D
Explanation:
141)
141)
A device used to evenly distribute mixtures of liquid and vapor refrigerant leaving the TEV to
multiple evaporator circuits is called a:
A)
Refrigerant manifold.
B)
Refrigerant junction.
C)
Refrigerant distributor.
D)
Refrigerant header.
Answer:
C
Explanation:
37
142)
142)
What senses the line temperature in electronic expansion valves?
A)
Bimetallic snap disks
B)
Magnetically ballasted electronic bulbs
C)
Thermistors
D)
Magnetic induction thermal energy sensors
Answer:
C
Explanation:
143)
143)
What is the advantage of balanced–port TEVs?
A)
Balanced port valves can retain good control over a wider range of operating conditions.
B)
Balanced port valves equalize on the off cycle, making it easier for the compressor to start.
C)
Balanced port valves can be installed upside down.
D)
Balanced port valves can be converted from externally equalized valves to internally
equalized simply by capping the equalizer port.
Answer:
A
Explanation:
144)
144)
Automatic expansion valves are good at maintaining a constant:
A)
Flow.
B)
Density.
C)
Viscosity.
D)
Temperature.
Answer:
D
Explanation:
145)
145)
Which of the following best describes the purpose of a distributor?
A)
To equally distribute cooling water
B)
To equally distribute gas
C)
To equally distribute refrigerant
D)
To equally distribute superheated liquid
Answer:
C
Explanation:
38
146)
146)
One operating advantage of fixed–restriction metering devices over expansion valves is:
A)
Higher operating efficiency.
B)
Can be used with low starting torque compressor motors.
C)
Easier to adjust.
D)
Improved system control.
Answer:
B
Explanation:
147)
147)
Why do standard–design thermostatic expansion valves need a minimum pressure drop to
operate correctly?
A)
To ensure that the pin seats tightly during operation
B)
The pressure difference across the pin acts as an opening force
C)
The bulb will not sense temperatures below 100 psig
D)
The internal adjustment springs have a minimum required torsion
Answer:
B
Explanation:
148)
148)
What is the evaporator saturation temperature of an R–410A system with a low–side pressure of
107 psig?
A)
107°F
B)
340°F
C)
30°F
D)
35°F
Answer:
D
Explanation:
149)
149)
Which of the following is the standard saturated temperature drop in the suction line?
A)
0°F
B)
2°F
C)
12°F
D)
7°F
Answer:
B
Explanation:
39
150)
150)
Thermostatic expansion valves respond to changes in:
A)
Subcooling.
B)
Temperature.
C)
Superheat.
D)
Pressure.
Answer:
C
Explanation:
151)
151)
Internally equalized thermostatic expansion valves:
A)
Allow the system pressures to equalize on the off cycle.
B)
Can be used on any type of system.
C)
Measure the evaporator pressure through a passageway inside the valve.
D)
Are constructed so that the pressures across the needle seat are equal.
Answer:
C
Explanation:
152)
152)
What is the purpose of TEV sensing bulbs with a limited, or gas charge?
A)
They reduce the amount of refrigerant in the system because of the limited charge.
B)
They save on installation cost by reducing the amount of charge in the TEV bulb.
C)
Gas–charged bulbs regulate better with systems experiencing liquid line flash gas.
D)
They produce a maximum operating pressure at high operating superheat.
Answer:
D
Explanation:
153)
153)
Thermostatic expansion valves are designed to maintain a constant:
A)
Superheat.
B)
Flow.
C)
Temperature.
D)
Pressure.
Answer:
A
Explanation:
40