Year 3A Questions
How much air volume in cfm is required across the evaporator of a 3-ton air conditioner for normal system operation? A. 1,200 B. 1,700 C. 1,000 D. 900
A. 1,200
Which method is often used to start a seized single-phase compressor? A. Apply a temporary capacitance boost B. Install a larger run capacitor C. Hit the compressor with a rubber mallet D. Double the applied voltage
A. Apply a temporary capacitance boost
A voltmeter measures 230V across the load side of a pair of fuses. What does this indicate? A. Both fuses are good. B. One fuse is open. C. One fuse has continuity. D. Both fuses are open.
A. Both fuses are good.
Which of the following traits is not seen with an undercharged system? A. Flooding B. Low subcooling C. Low suction pressure D. High superheat
A. Flooding
What is a major characteristic of the rotor in an ECM? A. It is a permanent magnet. B. It rotates in any direction. C. It is made of lightweight aluminum. D. It acts as an electromagnet when running.
A. It is a permanent magnet.
Which component is not in the circuit of a running CSR motor? A. Start capacitor B. Common winding C. Run capacitor D. Run winding
A. Start capacitor
From where does a geothermal heat pump extract heat? A. The Earth B. The surrounding air C. Deep wells D. Lakes and ponds
A. The Earth
Refrigerant entering an evaporator coil is a_____. A. cold, low-pressure liquid/vapor mix B. hot, high-pressure gas C. cool, low-pressure vapor D. warm, high-pressure liquid
A. cold, low-pressure liquid/vapor mix
The control used to energize the furnace blower motor is a(n)_____. A. fan switch B. thermocouple C. inducer switch D. limit switch
A. fan switch
The dimples inside the crimped barrel of a crimp connector are there to _____. A. improve conductivity B. prevent deforming of the barrel C. provide a better grip D. provide strain relief
A. improve conductivity
Resistance accuracy of a thermistor at a given temperature is best checked with a _____. A. resistance vs temperature chart B. digital ohmmeter C. heat gun and voltmeter D. digital ohmmeter and oscilloscope
A. resistance vs temperature chart
To speed up assembly of sheet metal duct systems, use_____. A. self-drilling screws B. wing nuts C. toggle bolts D. thread-cutting screws
A. self-drilling screws
To keep a nut from loosening, use a(n) _____. A. slotted nut B. flange nut C. wing nut D. acorn nut
A. slotted nut
The measured output voltage of a circuit breaker should be_____. A. the same as the input voltage B. within ±10% of the input voltage C. always lower than the input voltage D. slightly less than the input voltage
A. the same as the input voltage
Voltage measured at the compressor contactor should be_____. A. ±10% of nameplate voltage B. no more than 240V C. no more than 440V D. ±2% of nameplate voltage
A. ±10% of nameplate voltage
A furnace and air conditioner share the same 24V control circuit transformer. The air conditioner operates properly, but the furnace burners will not light. Which of the following is not the problem? A. Gas valve B. 24V transformer C. Low gas pressure D. Thermocouple
B. 24V transformer
What is an acceptable resistance to ground reading for a 440V motor? A. zero ohms B. 440,000 ohms C. Infinity D. 220,000 ohms
B. 440,000 ohms
A reading of 15 ohms is obtained across the coil of a relay. What does this indicate? A. An open relay B. A good relay C. A bad relay D. A partial short
B. A good relay
Which statement about ECMs is incorrect? A. All versions contain a 5-pin power connector. B. A universal replacement ECM is available. C. One motor can operate on two voltages. D. Power is always available to ECMs.
B. A universal replacement ECM is available.
What is the normal temperature difference between the air entering and air leaving the evaporator in an air conditioning system? A. About 5°F B. About 20°F C. About 10°F D. About 30°F
B. About 20°F
How long should a field-applied electrical termination last? A. Until the conductor's insulation fails B. As long as the conductor is in service C. As long as the equipment warranty D. 5 to 10 years
B. As long as the conductor is in service
Which of the following is not done during a preliminary inspection? A. Check condense coil cleanliness. B. Check voltage at the contactor. C. Check blower motor speed tap settings. D. Check air filter cleanliness.
B. Check voltage at the contactor.
What is the most common failure mode for start relays? A. Open coil B. Closed contacts C. Open capacitor D. Open contacts
B. Closed contacts
Which procedure about adding oil to a compressor is incorrect? A. Run the compressor before changing oil. B. POE oil must be poured in. C. Use the exact oil specified. D. Oil is added using a pump.
B. POE oil must be poured in.
Which of the following conditions will not cause flooding in a system with a TXV? A. Wrong sensing bulb location B. Plugged filter-drier C. Poor sensing bulb contact D. Light system load
B. Plugged filter-drier
Which of the following would not cause slugging? A. Buried refrigerant lines B. Refrigerant undercharge C. Oil overcharge D. Failed crankcase heater
B. Refrigerant undercharge
Across which set of single-phase motor windings will the highest resistance be measured? A. Common to start B. Start to run C. Common to L1 D. Common to run
B. Start to run
Which type of switch often contains a factory-installed jumper? A. manual reset limit switch B. combination fan/limit switch C. differential pressure switch D. furnace limit switch
B. combination fan/limit switch
With electronic room thermostats, the length of time of the burner is on is controlled by the_____. A. cooling compensator B. cycle rate adjustment C. heat anticipator D. burner input rate
B. cycle rate adjustment
Noise and vibrations from a furnace can be prevented from being transmitted through the sheet metal duct system by_____. A. adding vibration isolators to the blower motor B. flexible canvas vibration eliminators C. flexible metal vibration eliminators D. placing the furnace on a rubber pad
B. flexible canvas vibration eliminators
A system overcharge will cause_____. A. high head pressure and high superheat B. high suction and discharge pressures C. low suction pressure and low superheat D. high suction pressure and high superheat
B. high suction and discharge pressures
During heating operation, hot discharge gas is directed to the_____. A. heating coil B. indoor coil C. condenser coil D. outdoor coil
B. indoor coil
When replacing the liquid line filter-drier after a severe motor burnout, always_____. A. remove filter-drier isolation valves B. install one of the next larger size C. install a bi-flow filter-drier D. install one of the same size
B. install one of the next larger size
A restriction is often mistakenly diagnosed as a(n)_____. A. low superheat B. low charge C. overcharge D. oversized evaporator
B. low charge
A seismic restraint is designed to_____. A. Allow equipment operation during earthquakes. B. prevent excessive equipment movement C. reduce noise levels in equipment rooms D. prevent vibrations from being transmitted to ducts
B. prevent excessive equipment movement
A room thermostat should be mounted_____. A. above a supply register B. to avoid drafts C. on an outside wall. D. near the furnace
B. to avoid drafts
Toggle bolts are typically used _____? A. when heavy weight must be secured B. to fasten objects to hollow walls C. to fasten objects to masonry D. to fasten objects to solid walls
B. to fasten objects to hollow walls
When troubleshooting a problem, 24V is found on one side of a pressure switch but not on the other side. What does this indicate? A. No system pressure B. A closed pressure switch C. An open pressure switch D. Normal operation
C. An open pressure switch
What do the simplest thermostats use to sense temperature and activate a switch? A. Mercury bulb B. Thermocouple C. Bimetal D. Copper strip
C. Bimetal
Which of the following is not part of the thread designation of a bolt? A. Threads-per-inch B. Thread series symbol C. Grade designation D. Diameter
C. Grade designation
Which of the following symptoms does not indicate a low-capacity compressor? A. Low discharge pressure B. Low compressor current C. High compressor current D. High suction pressure
C. High compressor current
Which of the following is not a correct description of the system pressure between the compressor outlet and the metering device? A. Head pressure B. High-side pressure C. Low-side pressure D. Discharge pressure
C. Low-side pressure
A residential air handler is suspended from roof rafters using four threaded rods. How many vibration isolators are needed in this installation? A. One on each roof rafter B. One on the bottom of the air handler C. One on each threaded rod D. One under the blower assembly
C. One on each threaded rod
Which of these types of screws is headless? A. Phillips B. Cap C. Setscrew D. Tapcon
C. Setscrew
Why are programmable thermostats so popular? A. They use microprocessors. B. They are easy to install. C. They save energy. D. They look good.
C. They save energy.
With a mild compressor burnout, where are most of the system contaminants found? A. Within the evaporator B. Within the condenser C. Within the compressor D. Throughout the system
C. Within the compressor
How much higher than normal compressor amperage is locked rotor amperage? A. five to ten times higher B. Twice as high C. four to six times higher D. 20 times higher
C. four to six times higher
Which of the following devices must not be used as protection against seismic events for an air handler? A. snubbers B. open-spring devices C. housed-spring devices D. bumpers
C. housed-spring devices
To prevent a pulley from slipping on a rotating shaft, use a _____. A. retaining ring B. pop rivet C. key D. heli-coil
C. key
Subcooling can take place in the condenser coil and the _____. A. metering device B. evaporator coil C. liquid line D. hot gas line
C. liquid line
Steam build-up in a boiler is prevented by a(n)_____. A. aquastat B. zone valve C. low water cutoff D. reset controller
C. low water cutoff
With a standard heat/cool thermostat, the switch between heat and cool is done_____. A. electronically B. automatically C. manually D. with a relay
C. manually
The number that follows the first entry in the thread designation for a screw represents the _____. A. length of the screw B. diameter of the screw C. number of threads per inch D. thread class
C. number of threads per inch
The purpose of bumpers is to_____. A. serve as vibration isolators B. protect equipment during shipment C. restrain equipment in seismic events D. protect equipment in high-traffic areas
C. restrain equipment in seismic events
The speed of a multi-speed PSC blower motor can be changed by_____. A. increasing the pulley diameter B. changing the voltage C. selecting a different speed tap D. changing the run capacitor size
C. selecting a different speed tap
To allow system pressures to equalize before starting the compressor, a unit should contain a_____. A. freezestat B. lockout relay C. short-cycle timer D. solid-state relay
C. short-cycle timer
The main difference between a contactor and a motor starter is_____. A. the contactor has overload protection B. The contactor is only used to start compressors C. the motor starter has overload protection D. the contactor cannot be used to start a motor
C. the motor starter has overload protection
Required torque values are based on fastener diameter, type of metal, and _____. A. type of fastener head B. length of fastener C. threads per inch D. thread pitch
C. threads per inch
What is the approximate motor speed of a 6-pole motor running at 60Hz? A. 3,600 rpm B. 2.000 rpm C. 1,800 rpm D. 1,200 rpm
D. 1,200 rpm
How is a failed welded hermetic compressor removed from a unit? A. Cut refrigerant lines with a hacksaw. B. Remove refrigerant lines with a torch. C. Remove bolts from flanges. D. Cut refrigerant lines with a tubing cutter.
D. Cut refrigerant lines with a tubing cutter.
What is an important factor that must be considered when selecting the proper drive when the drive operates for less than 25% of the time? A. Motor size B. Torque value C. Environment D. Duty cycle
D. Duty cycle
Which device is an example of a sensing element? A. Relay contacts B. Gas valve C. Relay coil D. Humidistat
D. Humidistat
What will occur if stripping length is too long? A. Increased insulation support B. Reduced contact surface C. Acceptable contact surface D. Terminal screw interference
D. Terminal screw interference
What is an advantage of using dynamic DC braking for an AC motor? A. The motor stops slowly. B. It is ideal for suspended loads. C. The brake linings stay cool. D. The motor stops quickly.
D. The motor stops quickly.
Which of the VFD programmable parameters provides an automatic torque boost to the motor? A. Current limit B. Basic frequency reference C. V/Hz ratio D. V/Hz optimization
D. V/Hz optimization
The aquastat in a hydronic heating system _____. A. maintains water temperature B. controls oil burner operation C. prevents overheating D. all the above
D. all the above
Conductors should be stripped only with a(n)_____. A. notched knife blade B. high-temperature heat gun C. very sharp knife blade D. appropriate stripping tool
D. appropriate stripping tool
The device that helps turn on cooling equipment before the room gets too warm is called a_____. A. cooling anticipator B. heat anticipator C. differential compensator D. cooling compensator
D. cooling compensator
If the reversing valve fails in the de-energized position during the heating mode, all the following will continue to function except_____. A. the compressor B. the crankcase heater C. the outdoor fan D. defrost
D. defrost
A plug tap is used_____. A. when starting a tapping operation B. where very tight fits are needed C. for threading the bottom of a hole D. following the taper tap
D. following the taper tap
A simplified schematic diagram that can aid in troubleshooting is called a_____. A. component arrangement B. legend C. note D. ladder diagram
D. ladder diagram
When equipment is installed, compressor hold-down bolts must be _____. A. torqued-down B. installed C. tightened D. loosened
D. loosened
To prevent a condensing unit from operating at low outdoor temperatures, use a(n)_____. A. freezestat B. low-pressure switch C. lockout relay D. outdoor thermostat
D. outdoor thermostat
The type of lock washer commonly used with bolts and cap screws is the _____. A. countersunk lock washer B. external lock washer C. internal lock washer D. split ring lock washer
D. split ring lock washer
A crankcase heater is designed to warm and thin the oil for better lubrication. True False
False
A measurement of infinite resistance across the secondary of a 24V transformer is an indication of an open secondary and a failed transformer. True False
False
A relay contact that is shown normally open on a schematic stays open when the relay is energized. True False
False
Acid can be formed in a refrigeration system only when compressor motor windings burn out. True False
False
All compressor types require that the oil be changed after a severe motor burnout. True False
False
Always measure the resistance of a start thermistor while it is hot. True False
False
If a system with a TXV hunts, it means there is something wrong in the system. True False
False
In a heat pump, the heat exchanging coils are called the evaporator coil and condenser coil. True False
False
It is usually a waste of time to discuss an equipment problem with a customer prior to troubleshooting. True False
False
Manufacturer's troubleshooting aids will always isolate the problem to a specific component. True False
False
The voltage balance percentage is obtained by dividing the average voltage by the maximum voltage deviation from average, multiplied by 100. True False
False
Using a VFD on an older motor allows the load capacity rating to be increased. True False
False
Voltage is measured across the coil of a contactor but the contactor does not energize. This indicates an open contactor coil. True False
False
217 volts is applied to a 240-volt motor. The motor should operate without any problem. True False
True
A major advantage of using ECMs is their quiet operation. True False
True
All observed system temperatures and pressures should be compared to normal readings recorded in the equipment operating log. True False
True
Another name for the function of controlled stopping in a VFD is soft stop. True False
True
Dirt is at the root of many evaporator and condenser coil airflow problems. True False
True
During heating operation, thermostat contacts must close when the room temperature drops. True False
True
Electronic solid-state relays are more reliable than conventional relays. True False
True
If a compressor has bad valves or rings, suction pressure will be high, discharge pressure will be low, and compressor motor current will be low. True False
True
If an ECM is defective, it is possible to replace just the control section. True False
True
The measured capacitance of a start capacitor is 17% higher than its stated value. This capacitor can still be safely used. True False
True
The severity of a compressor motor burnout affects the procedures for replacing the compressor. True False
True
The thermostat G terminal controls the indoor fan. True False
True
Two-stage heating thermostats are often used to control heat pumps. True False
True