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NATE Exam: Air Conditioning and Heat Pumps
Questions with 100% Correct Answers
- Which of the following factors affects a customer's level of comfort? a. Air movement b. Humidity c. Temperature d. All of the above - ✅✅✅d (All of the above: air movement, humidity, temperature)
- A cooling load calculation estimates the sensible heat gain of a structure. The maximum sensible capacity of a cooling-only system should be within ____% of this calculated value. a. ±10% b. +10% c. +15% d. +30% - ✅✅✅c (+15%)
- The maximum sensible cooling capacity of a heat pump should be within ____% of the calculated sensible heat gain of a structure with a large heating load.
a. ±10% b. +15% c. -25% d. +25% - ✅✅✅d (+25%)
- The combined output of a heat pump and its auxiliary heat should not exceed the calculated heat loss of a home by more than ____ %. a. 10% b. 15% c. 20% d. 25% - ✅✅✅b (15%)
- What amount of auxiliary electric heat is needed when the output of a heat pump on a design day equals 18,800 Btuh and the heat loss of a home is 29,700 Btuh? a. 2.1 kWh b. 3.2 kWh c. 5.0 kWh d. 10.9 kWh
- Note: 3,413 Btu/kW - ✅✅✅b (3.2 kWh)
- What is the primary danger to people near an accidental refrigerant release or spill? a. Blurred vision caused by the refrigerant vapor coming in contact with the eyes b. Changes in weather patterns caused by global warming c. Damage to the food chain caused by decreased ozone levels in the stratosphere d. Suffocation caused by the heavier refrigerant displacing oxygen in the air - ✅✅✅d (Suffocation caused by the heavier refrigerant displacing oxygen in the air)
- The maximum temperature at which refrigerant may be stored is ____°F when the container is no more than ____% full of liquid by volume. a. 120°F, 60% b. 125°F, 60% c. 125°F, 80% d. 135°F, 80% - ✅✅✅c (125°F, 80%)
- Boiling of the refrigerant occurs in which system component? a. Compressor b. Condenser
c. Evaporator d. Metering device - ✅✅✅c (Evaporator)
- Why is superheat necessary in a system that utilizes hermetic compressors? a. It ensures that dry vapor reaches the compressor so that mechanical damage does not occur b. It increases system capacity c. It prevents liquid refrigerant from gassing the metering device d. Superheat is necessary only when open compressors are being used - ✅✅✅a (It ensures that dry vapor reaches the compressor so that mechanical damage does not occur)
- When the heat load on an evaporator increases, what is the effect on the system? a. Suction pressure decreases and discharge pressure increases b. Suction pressure increases and discharge pressure decreases c. Suction pressure and discharge pressure both decrease d. Suction pressure and discharge pressure both increase - ✅✅✅d (Suction pressure and discharge pressure both increase)
a. Accumulator b. Compressor c. Condenser d. Evaporator - ✅✅✅b (Compressor)
- How are hermetic compressor motors cooled? a. With air drawn around the compressor shell by the condenser fan b. With water circulated through tubing wrapped around the compressor shell c. With suction vapor drawn from the evaporator d. With a combination of air and water - ✅✅✅c (With suction vapor drawn from the evaporator)
- Heat pump compressors sometimes run hotter than compressors used in cooling-only units because heat pump compressors ____. a. exhibit low refrigerant density at low suction pressures during the heating cycle b. pump liquid refrigerant during the cooling cycle c. must prevent ice formation during the defrost cycle d. must heat indoor spaces in the winter - ✅✅✅a (exhibit low refrigerant density at low suction)
- When is a crankcase heater most needed? a. Early in the morning during the cooling cycle b. When the compressor is operating in very cold winter weather c. When the compressor is operating in very humid conditions d. When the compressor is off - ✅✅✅d (When the compressor is off)
- Work done on the refrigerant in the condenser is transferred as ____. a. latent heat b. sensible heat c. specific heat d. both sensible and latent heat - ✅✅✅d (both sensible and latent heat)
- Why are more circuits needed in the outdoor coils used in heat pumps than in the condenser coils used in cooling-only units? a. To keep the pressure drop across the outdoor coil high b. To keep the pressure drop across the outdoor coil low c. To provide more subcooling during the cooling cycle
- What affect does a low refrigerant charge have on reversing valve operation? a. It causes the slider to overheat b. It creates a hissing sound in the reversing valve c. It increases the chance that the reversing valve will not be able to transfer properly d. It has no effect on reversing valve operation - ✅✅✅c (It increases the chance that the reversing valve will not be able to transfer properly)
- When adding a heat pump to an existing fossil-fuel furnace, an installer must do all of the following except ____. a. add a control to prevent the heat pump and furnace from operating at the same time during normal heating b. confirm there is adequate clearance around the outdoor section for good air flow c. level the indoor coil's condensate pan to ensure proper drainage of condensate water d. make sure that the number of fins per inch of the new coils equals that of the replaced coils - ✅✅✅d (make sure that the number of fins per inch of the new coils equals that of the replaced coils)
- What is the purpose of a receiver?
a. It prevents liquid refrigerant from slugging the compressor b. It removes heat from refrigerant vapor c. It returns oil to the compressor at a rate the compressor can tolerate d. It stores liquid refrigerant - ✅✅✅d (It stores liquid refrigerant)
- What is the typical storage life of modern refrigerants? a. 5 to 10 years b. 10 to 20 years c. 20 to 30 years d. Modern refrigerants have an indefinite storage life - ✅✅✅d (Modern refrigerants have an indefinite storage life)
- Which of the following should be used to leak-test refrigerant tubing? a. Compressed air b. Dry nitrogen c. Oxygen d. Water - ✅✅✅b (Dry nitrogen)
- Of the motors commonly used in HVACR systems, which type has the lowest starting torque?
c. 40-A d. 60-A - ✅✅✅d (60-A)
- Voltage supplied to a motor may vary from the rated voltage by ____%. a. +0%, -0% b. +0%, -10% c. +10%, -0% d. +10%, -10% - ✅✅✅d (+10%, -10%)
- What is one of the most important reasons for using electronic controls in HVACR systems? a. The Clean Air Act of 1990 mandates their use b. They are less expensive than the controls they replace c. They are lighter in weight than the controls they replace d. They make decisions based on many inputs - ✅✅✅d (They make decisions based on many inputs)
- Hard-start kits are often needed on ____. a. reciprocating compressors used with TEVs b. rotary compressors used with fixed metering devices c. scroll compressors used with TEVs
d. three-phase compressor used with fixed metering devices - ✅✅✅a (reciprocating compressors used with TEVs)
- A 24-V transformer with a 40-VA rating can operate safely with a current of ____. a. 6.0 mA b. 960.0 mA c. 0.6 A d. 1.67 A - ✅✅✅d (1.67 A)
- Some electromechanical thermostats must be connected to both sides of the transformer in order to power the ____. a. cooling anticipator b. display lights on the subbase c. heat anticipator d. microprocessor - ✅✅✅b (display lights on the subbase)
- A cooling anticipator in the control circuit is connected in ____ with the ____ switch of the thermostat. a. parallel, cooling b. parallel, heating c. series, cooling d. series, heating - ✅✅✅a (parallel, cooling)
b. Voltage to the heater with current draw through the heater elements c. Voltage to the heater with no current draw through the heater elements d. voltage to the heater with resistance measured by an ohmmeter - ✅✅✅c (Voltage to the heater with no current draw through the heater elements)
- Which of the following functions occur when a heat pump goes into a defrost cycle? a. The auxiliary heat comes on, the outdoor fan stops running, and the reversing valve switches to the cooling mode b. The outdoor fan stops running and the reversing valve switches to the cooling mode c. The reversing valve switches to the cooling mode and the auxiliary heat comes on d. The reversing valve switches to the heating mode, the outdoor fan stops running, and the auxiliary heat comes on - ✅✅✅a (The auxiliary heat comes on, the outdoor fan stops running, and the reversing valve switches to the cooling mode)
- What internal voltage is likely to be measured in an electronic air cleaner? a. 24 V
b. 120 V c. 380 V d. 5,000 V
- See page 81 - ✅✅✅d (5,000 V)
- What precaution must you take when installing a dual-fuel split system? a. The control system must not allow the heat pump and furnace to operate at the same time during normal heating cycle b. The high-limit switch on the heat pump must be replaced with one that has a lower temperature setting c. The high-limit switch on the heat pump must be replaced with on that has a higher temperature setting d. The limit control on the furnace must be replace with one that has a manual reset - ✅✅✅a (The control system must not allow the heat pump and furnace to operate at the same time during normal heating cycle)
- What problem is likely to occur if a proper trap is not used on the condensate drain for a draw-through unit? a. Condensate water will not drain properly and will back up above the primary drain
a. be connected to the primary condensate drain line using an approved P-trap b. be terminated at some conspicuous location so that an overflow is readily noticed c. have a diameter of at least 1 in. d. never be insulated - ✅✅✅b (be terminated at some conspicuous location so that an overflow is readily noticed)
- Which of the following statements about a packaged unit installation is true? a. Packaged heat pumps are intended for rooftop installations only b. Packaged heat pumps are more difficult to install than split systems c. Packaged heat pumps are not available for use in commercial applications d. The pad used to support a packaged heat pump should not make contact with the building - ✅✅✅d (The pad used to support a packaged heat pump should not make contact with the building)
- Which of the following brazing materials is acceptable for use on refrigerant piping? a. 50/50 soft solder with an approved flux b. 95/5 soft solder with an approved liquid flux
c. 95/5 soft solder with an approved paste flux d. Brazing allow with an approved flux
- See pages 97, 101 - ✅✅✅d (Brazing allow with an approved flux)
- What type of flame is recommended for brazing refrigerant piping? a. Acetylene flame b. Carbonizing flame c. Neutral flame d. Oxidizing flame
- See page 100 - ✅✅✅c (Neutral flame)
- Why must you exercise special care when you bend soft- drawn refrigerant tubing? a. Any distortion of the tubing diameter creates a restriction to refrigerant flow that reduces system capacity b. Copper flakes can come loose from interior surfaces of the tubing if it is overbent c. Overbending the tubing makes it difficult to slide on the close-cell insulation
