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