NATE Exam Air Conditioning and Heat Pumps questions with 100% Correct Answers 2024/2025, Exams of Physics

Download NATE Exam Air Conditioning and Heat Pumps questions with 100% Correct Answers 2024/2025 and more Exams Physics in PDF only on Docsity! NATE Exam Air Conditioning and Heat Pumps questions with 100% Correct Answers 2024/2025 Which of the following factors affects a customer's level of comfort? a.Air movement b.Humidity c. Temperature d.All of the above - correct answer 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% - correct answer 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% - correct answer 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% - correct answer 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 a. Compressor b.Condenser c. Evaporator d.Metering device - correct answer 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 - correct answer 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 - correct answer d (Suction pressure and discharge pressure both increase) What type of energy is transferred when work is done in the condenser? a. Latent heat energy b.Sensible heat energy c. Both latent and sensible heat energy d.Neither latent nor sensible heat energy - correct answer c (Both latent and sensible heat energy) What is the primary function performed by a thermal expansion valve? a. It maintains the correct superheat in the hot vapor leaving the compressor b. It maintains the correct superheat in the suction vapor leaving the evaporator c. It maintains the proper subcooling level in the liquid refrigerant d. It prevents flash vapor bubbles from developing in refrigerant entering the evaporator - correct answer b (It maintains the correct superheat in the suction vapor leaving the evaporator) Which component pumps refrigerant through the system and raises the vapor temperature? a.Accumulator b.Compressor c. Condenser d.Evaporator - correct answer 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 - correct answer 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 - correct answer 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 - correct answer 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 - correct answer d (both sensible and latent 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 - correct answer 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 - correct answer 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 - correct answer 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 - correct answer b (Dry nitrogen) Of the motors commonly used in HVACR systems, which type has the lowest starting torque? a. PSC motor b.Shaded-pole mole c. Split-phase motor d.Three-phase motor - correct answer b (Shaded-pole motor) What is the typical phase angle for a split-capacitor motor? a. 15° b.30° c. 75° d.90° - correct answer b (30°) What determines the staging of a two-speed compressor in a heat pump application? a. Deviation from setpoint of the thermostat b.Discharge pressure c. Outdoor ambient d.Suction vapor temperature - correct answer a (Deviation from setpoint of the thermostat) The NEC approves a dual-element time-delay fuse as overcurrent protection for a 20-A motor? a. 20-A b.30-A c. 40-A d.60-A - correct answer d (60-A) Voltage supplied to a motor may vary from the rated voltage by %. According to Ohm's Law, what will happen if voltage to a heater element is increased by 10%? a. The Btuh output will increase by 5% b.The current draw will decrease by 10% c. The current draw will increase by 10% d.The heater will overheat - correct answer c (the current draw will increase by 10%) When air flow through an electric heater is not sufficient, the technician will observe . a. fusible links glowing red or orange b.heater elements glowing red or orange c. higher-than-normal voltage readings d. lower-than-normal voltage readings See page 78 - correct answer b (heater elements glowing red or orange) Which of the following combination of measurements indicates an open heater element? a. Current draw through the heater elements with no voltage to the heater 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 - correct answer 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 - correct answer 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 - correct answer 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 - correct answer 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 b.Conditioned supply air will escape through the condensate drainpipe c. Ice will accumulate on the evaporator coil d. Stress on the connection fitting at the evaporator will cause the pipe to crack See pages 89-90 - correct answer a (Condensate water will not drain properly and will back up above the primary drain) Which of the following issues affects the decision to use a running trap on a condensate line at the evaporator coil? a. Running traps are better at draining condensate water than P-traps b.Running traps are easier to clean than other types of condensate traps c. Running traps do not allow for the proper drainage of condensate water d.Running traps stop air from being drawn into the air handler in a draw-through application d.The refrigeration flow rate increases if tubing is overbent, making oil return impossible - correct answer a (Any distortion of the tubing diameter creates a restriction to refrigerant flow that reduces system capacity) The evacuation of a refrigerant circuit is considered complete when a vacuum of can be maintained. a. 200 microns b.350 microns c. 500 microns d.1,000 microns - correct answer c (500 microns) As the length of electrical wire increases, its resistance while the temperature is maintained at a constant level. a. decreases b. increases d. remains unchanged c. varies unpredictably - correct answer b (increases) What is the thermal balance point of a heat pump system? a. The indoor air temperature at which the blower fan speed must be increased in order to maintain the space temperature setpoint b.The outdoor air temperature at which the heat pump initiates a defrost cycle c. The outdoor air temperature at which output of the gas furnace in a dual-fuel application equals the heat loss of the home d.The outdoor air temperature at which the output of the heat pump equals the heat loss of the home - correct answer d (The outdoor air temperature at which the output of the heat pump equals the heat loss of the home) What voltage is measured between any two legs of the three hot legs in a delta- connected 240-V three-phase distribution panel? a. 208 V b.240 V c. 277 V d.380 V See page 107 - correct answer b (240 V) Which of the following statements about the installation of an electric air cleaner (EAC) is true? a.An EAC should be wired so that it operates only when the ON/OFF switch is in the "ON" position and the supply air blower is operating b.The control voltage supplied to an EAC can be as high as 5,000 V c. The primary function of an EAC is odor removal d.When the relative humidity is low, an EAC should be operated only in the heating mode - correct answer a (An EAC should be wired so that it operates only when the ON/OFF switch is in the "ON" position and the supply air blower is operating) What is the indoor air flow for an electric furnace when the supply air temperature is 98°F, the return air temperature is 70°F, the voltage supplied to the furnace is 220 V, and the current draw of the furnace is 47 A? a. 1,060 CFM b.1,170 CFM c. 1,260 CFM d.1,370 CFM Note: b. connected in series with the control switch c. normally closed limit switches d.open at the same time in order to protect the load - correct answer b (connected in series with the control switch) Which of the following statements about SI wiring diagrams is true? a. High-voltage wiring circuits are shown above the power wiring b.High voltage wiring circuits are shown below the power wiring c. Low-voltage wiring circuits are shown below the power wiring d.Power wires are drawn as perimeter lines with circuits drawn between the power wires - correct answer b (High-voltage wiring circuits are shown below the power wiring) Which of the following types of wiring diagrams is best suited for troubleshooting electric circuits? a. Installation diagram b.Ladder schematic c. Pictorial diagram d.Point-to-point diagram - correct answer b (Ladder schematic) Exposure to an electric current of mA can be fatal if it lasts for one second or more. a. 1 mA b.10 to 20 mA c. 50 to 75 mA d.100 to 200 mA See pages 145-146 - correct answer d (100 to 200 mA) The use of a ground fault circuit interrupter (CFCI) is especially important when . a. apprentice workers are asked to use power tools b.more than one electric tool is plugged into an outlet c. the cord of an electric tool is frayed or cracked d.work is being done on wet surfaces - correct answer d (work is being done on wet surfaces) An auto-ranging meter automatically finds the best measurement range to display the quantity of being measured. a. amperes or ohms b.amperes or volts c. ohms or volts d. amperes, ohms, volts - correct answer d (amperes, ohms, volts) What ANSI category is best for meters used in HVACR electrical work, and why? a. CAT I, because most HVACR electrical work is done on control circuits b.CAT II, because most HVACR electrical work is done on appliances that plug into wall receptacles c. CAT III, because most HVACR electrical work is done on appliances that are permanently installed d.CAT IV, because most HVACR electrical work is done on utility connections - correct answer c (CAT III, because most HVACR electrical work is done on appliances that are permanently installed) What critical first step must be taken to begin the troubleshooting process? a. Check all fuses for continuity b.Check for grounded motor windings c. Check relay and contactor housings for stuck switches d.Check that the correct voltage is being supplied to the equipment - correct answer d (Check that the correct voltage is being supplied to the equipment) A good fuse will yield a reading of on an ohmmeter. a. 0 Ω b. less than 1 Ω c. infinity d. a value that rises quickly to 0 before falling slowly toward infinity - correct answer a (0 Ω) Which of the following low-voltage wires is typically used to carry power to the thermostat subbase? a. Green b. contacts are pitted c. motor capacitor is defective d.wrong voltage is supplied to the unit - correct answer b (contacts are pitted) Which of the following devices is not a safety device used in electric heaters? a. Fusible link b.High-limit switch c. Main circuit fuse d.Sequencer See page 159 - correct answer d (Sequencer) A resistance reading of infinity between the "R" terminal and the "S" terminal of a compressor motor indicates a(n) . a. grounded motor winding b.open motor winding c. shorted motor winding d. tripped internal overload - correct answer b (open motor winding) An acceptable capacitance reading for a run capacitor is the microfarad rating printed on the capacitor. a. equal to or up to 10% more than b.equal to or up to 20% more than c. plus or minus 10% of d.plus or minus 20% of - correct answer c (plus or minus 10% of) What air volume flow rate of recirculated indoor air equals one ton of cooling load on the evaporator? a. 300 cfm b.350 cfm c. 400 cfm d.450 cfm - correct answer c (400 cfm) What heat quantity equals one ton of total cooling load on the evaporator? a. 7,500 Btuh b.10,000 Btuh c. 12,000 Btuh d.15,000 Btuh - correct answer c (12,000 Btuh) Which of the following is measured to determine the total resistance to air flow in a ductwork system? a. Current draw of the compressor motor b.External static pressure at the air handler or furnace c. Power input to the electric heater d.Temperature rise across the electric heater - correct answer b (External static pressure at the air handler or furnace) External static pressure is the sum of the and the . a. absolute static pressure entering the air filter, absolute static pressure leaving the air filter b. absolute static pressure entering the indoor blower, absolute static pressure leaving the indoor blower d.225°F - correct answer d (225°F) What problem results when the limit temperature of the discharge line at the compressor is exceeded? a. Evaporator superheat will be excessive, causing capacity loss b.Gassing of the indoor metering device will occur during the cooling cycle c. Subcooling in the condenser will decline to a dangerously low level d.Temperature in the compressor will be high enough to vaporize the lubricant - correct answer d (Temperature in the compressor will be high enough to vaporize the lubricant) A system should be operated for at least before heat measurements are taken. a. 20 minutes b.30 minutes c. 45 minutes d.1 hour - correct answer a (20 minutes) What level of vacuum is needed to ensure that a sufficiently deep vacuum has been drawn for the removal of water vapor? a. 500 microns b.1,000 microns c. 2,500 microns d.25,000 microns - correct answer a (500 microns) What potential problem is associated with the use of dye injected for the purpose of leak detection? a. Dye can damage a technician's refrigerant manifold gauges b.Dye can increase the pumping ratio of the compressor c. Overuse of dye can change the mixing properties of refrigerant and oil d.Overuse of due can create acids in the oil See page 186 - correct answer c (Overuse of dye can change the mixing properties of refrigerant and oil) What gas must be purged through a refrigerant circuit to prevent the formation of oxides whenever brazing is being done? a.Any HFC b.Dry nitrogen c. Filtered air d.Oxygen - correct answer b (Dry nitrogen) What certification is required before a technician is permitted to work on air conditioning and heat pump systems? a.ARI 77-88 certification b.EPA Section 608 certification c. EPA Section 609 certification d. Journey or Master Mechanical tradesman license - correct answer b (EPA Section 608 certification)