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NATE AC Service Certification QUESTIONS
WITH COMPLETE 100% VERIFIED
SOLUTIONS 2024/
A system is supplied from the factory with charge of 5 pounds 10 ounces for a 15 foot line set. The line set is 25 feet long. The manufacturer's instruction sheet specifies 0.6 ounces of refrigeration to be added for each added foot of refrigerant line set length. What is the total refrigerant charge for the system? A. 6 ounces B. 5 pounds C. 5 pounds 10 ounces D. 6 pounds D. 6 pounds 15ft - 25ft = 10ft x .6 = 6 ounces 5 pounds + 10 ounces + 6 ounces 5 pounds + 16 ounces = 6 pounds The purpose of using flux when soldering is to: A. anneal the surface. B. give better heat flow. C. reduce oxidation. D. pre-seal the oxidation. C. reduce oxidation. Outdoor condensing units that are installed in areas where flooding is possible must: A. be mounted above flood level. B. utilize NEMA 1 enclosures. C. be mounted under an overhanging eave. D. use water resistant components. A. be mounted above flood level. The component used to reduce sound transmission and prevent water leaks on a rooftop air conditioner packaged unit installation is the:
A. curb gasket. B. silicone caulk. C. roof flashing. D. roofing tar. A. curb gasket. Return air leakage in a hot attic will: A. Increase capacity B. Decrease capacity C. Increase airflow D. Decrease airflow B. Decrease capacity An air conditioner refrigerant circuit should be evacuated to a minimum of: A. 0 microns. B. 200 microns. C. 500 microns. D. 1200 microns. C. 500 microns. Which of the following substances could create an extremely dangerous condition if used to check refrigeration system for leaks? A. R- 22 B. Nitrogen C. Oxygen D. Carbon Dioxide D. Carbon Dioxide The subcooling method for checking charge is generally used on air conditioners with what type of metering? A. Only externally equalized thermostatic expansion valves B. Any thermostatic expansion valve C. Piston type D. Any fixed metering device B. Any thermostatic expansion valve
Which measures duct static pressure? A. Anemometer B. Air balance hood C. Mechanical velometer D. Differential pressure gauge C. Mechanical velometer A duct 36 in. x 24 in. that has an average velocity of 600 fpm is handling: A. 3600 CFM. B. 2400 CFM. C. 1200 CFM. D. 1000 CFM. A. 3600 CFM. CFM = Velocity x Area (ft.^2) CFM = 600fpm x ((36 x 24)/144)) (convert to sq. ft.) CFM = 600fpm x 6sqft CFM = 3600 CFM What steps are necessary to clean a two row curved condenser coil? A. Spray the coil from the inside of the condenser with a soap base coil cleaner B. Spray the coil from the inside and the outside of the condenser with an acid base cleaner C. Brush the outside of the condenser with a bristle brush and water flush D. Separate the two rows of coils, spray all surfaces with proper coil cleaner and water flush *D. Separate the two rows of coils, spray all surfaces with proper coil cleaner and water flush A residential supply diffuser that is noisy because of a loose vane is best serviced by: A. reducing the air volume. B. changing the fan speed. C. replacing the noisy vane. D. replacing the diffuser. D. replacing the diffuser. Which of the following is a likely problem if the air across the evaporator of an air conditioner has a high temperature differential? A. Too much charge
B. Clogged expansion valve C. Dirty filter or evaporator D. Dirty condenser coil *C When performing a cycling check during a maintenance call, the technician should first check with the owner of the equipment for their opinion of performance. The next step is to turn the unit off at the thermostat SYSTEM switch. The technician should set the FAN switch to: A. AUTO and measure the voltage from the R to G terminal. B. ON and measure the voltage from the R to the W1 terminal. C. ON and check that the blower is running. D. AUTO and check that the blower is running. *C To properly check the computer and its line voltage wiring the technician should measure resistance at the: A. load side of the compressor contactor. B. compressor terminals. C. capacitor. D. crankcase heater. *A On a residential no cooling call, typically the first check would be: A. the air filter. B. the control voltage at the transformer. C. if the thermostat is calling for cooling. D. the refrigerant system pressures. C. if the thermostat is calling for cooling. What could cause a customer to complain that their home feels damp or "sticky"? A. Low evaporator airflow B. Returns may be pulling in unconditioned air C. The system is undersized D. Air filter is clogged or dirty B. Returns may be pulling in unconditioned air A system supply airflow check is used to diagnose:
C. 16degF D. 8degF D. 8degF What is the maximum acceptable supply voltage tolerance for a 120 V circuit? A. +/-3% B. +/-5% C. +/-10% D. +10% / - 15% B. +/-5% a compressor with proper voltage and a hard start relay and capacitor draws lock rotor amps on startup. Which of the following is most likely the problem? A. The unit is overcharged. B. The potential relay is open. C. The start and run windings are open. D. The pressure difference on the compressor is too great. *B With the thermostat blower switch set to ON, which of the following measurements indicates a call for residential indoor blower operation? A. 0 volts at the load side of the relay B. 24 volts at the load side of the relay C. 0 volts at the relay coil D. 24 volts at the relay coil *B A 120V x 24V step down transformer has a rating of 40 VA. This transformer must not be connected to a load above what current draw? A. 0.3 amps B. 0.6 amps C. 1.7 amps D. 3.0 amps C. 1.7 amps What does a bright red or orange glow from the resistance elements in a duct heater indicate? A. Flow of air is insufficient.
B. Line voltage is insufficient. C. Supply wires are oversized. D. Duct heaters are operating properly. A. Flow of air is insufficient. During an annual service check up, it is discovered that there is a moderate amount of resistance on a "bellyband" crankcase heater. What does this condition indicate? A. The crankcase heater will operate B. Line voltage is insufficient. C. Supply wires are oversized. D. Duct heaters are operating properly. *A If an air conditioning system needs to operate in a low ambient condition, the condenser may become too efficient. What happens to condenser operation and what can be done to counteract this condition? A. The head pressure becomes too low and the superheat needs to be lowered B. The head pressure becomes too low and the superheat needs to be raised C. The head pressure becomes too low and the condenser fan motor needs to be slowed or stopped D. The suction pressure becomes too high and a low ambient controller will lower it *B Will a Capacitor Start-Capacitor Run (CSCR) motor that has an open run capacitor start? A. No, it would be unable to start without the run capacitor B. It may start, but it draws a higher than normal running current C. Yes, it will start, but it will run backwards D. It can only start if the voltage is higher *A Which microfarad value indicates a good start capacitor rated at 145-175 mfd? A. 130 B. 160 C. 180 D. 190 B. 160
Which of the following are the first two checks typically made on an electronic control? A. Presence of proper input signals and proper output voltages B. Presence of any on board transformer voltages and proper output voltages C. Ohm check of all sensors and solder side continuity checks D. Continuity of all terminals and component side checks A. Presence of proper input signals and proper output voltages How should a technician evaluate the circuitry when the wiring diagram is missing? A. Use a diagram from a similar equipment model B. Completely rewire the unit C. Redraw the circuits on a sketch pad D. All equipment is wired the same *A In a low voltage circuit, a corroded wire-to-terminal connection acts in the circuit like a(n): A. additional inductor. B. additional capacitor. C. additional resistor. D. low ohm short. C. additional resistor The continuity reading on a functional fuse will be: A. 0 ohms. B. 50 - 100 ohms C. 500 - 1000 ohms D. infinite ohms. *A Where should a technician check the voltage to an energized compressor? A. At the main electrical panel B. At the line side of the compressor contactor C. At the load side of the compressor contactor D. At the unit disconnect *C The following conditions exist in a circuit that supplies power to three phase parallel loads. *One load is resistive,
*One load is capacitive, *One load is inductive The total current in the circuit when operating will be: A. the resistive current plus the inductive current minus the capacitive current. B. the resistive current alone since the inductive current will always be cancelled by the capacitive current. C. the average of the currents flowing through each load. D. the sum of the currents through each load. D. the sum of the currents through each load. If the technician beleives that a hermetic compressor has a permanently open internal overload protector, the technician should test the compressor while it is: A. cool. B. bypassed. C. hot. D. running. A. cool. diagram #50 missing page # Using the diagram above, what is the voltage across T1 & L1 with the compressor contactor de- energized and compressor winding intact? A. 0V B. Less than 120V C. 120V D. 230V
diagram Refer to the diagram above and answer the question: When troubleshooting an energized electrical circuit on an electric heat section, 244 volts is measured across the element at points A and B and no amperage is measured. What is the problem with this system? A. The element has a short in it B. The element is shorted to ground C. A fuse link is open D. The electric element is open
C. Look for a directional arrow on the side of the blower wheel D. Start the motor and use hand to detect the presence of air flow *A After startup, a technician finds a noise problem caused by a metal supply register with several severely bent vanes. What repairs should be made to eliminate the noise? A. Cover the backside of the misaligned vanes with ducts tape B. None, the entire register should be replaced C. Reduce airflow to the noisy register D. Realign the misaligned van with pliers *B The technician has determined a supply in a flexible duct system is leaking. Which of the following should be checked? A. All connections and outer layers of duct only B. All take-off connections and outer layers of duct only C. All connections and longitudinal seams D. All connections including inner and outer layers D. All connections including inner and outer layers How would a technician repair a 1" hole in a section of duct board? A. Cut out the hole, and fabricate, staple and tape a plug in place to fill the hole B. Cut out the hole and fabricate and tape a plug in place to fill the hole C. Cut out the hole and seal over the location with foil tape and mastic D. Replace the entire section of duct board *C Service site conditions are: *House feels "drafty" in cooling, *Properly sized 3-1/2 ton split system, *High supply face velocities *Ductwork is properly sized, *Total CFM 1400 What do these readings indicate? A. The system is operating normally and there is nothing wrong B. The returns are undersized
C. The system is operating normally but the supply registers are too restrictive D. The blower is set at too high CFM C. The system is operating normally but the supply registers are too restrictive In a simple refrigeration system, the refrigerant boils in the: A. metering device. B. compressor. C. evaporator. D. condenser. C. evaporator. To achieve a specific SEER rating, which components must be matched? A. Condensing unit and evaporator B. Compressor and metering device C. Evaporator and metering device D. Compressor and condenser A. Condensing unit and evaporator Suction line insulation is important to control condensation and to: A. minimize heat transfer. B. maximize heat transfer. C. prevent flash gas. D. improve subcooling. A. minimize heat transfer. In a economizer system, the enthalpy control is used to measure: A. moisture content. B. humidity of ambient air. C. outside air temperature. D. both temperature and moisture content. *C Other than using a two stage compressor, what is another method for capacity control? A. Two stage thermostat B. Multiple compressors C. Liquid line receiver D. Stage outdoor fan
C. Air moves vertically up the fins and out the top D. Air moves vertically down the fins and out the top *A Which of the following can cause a lower than normal suction pressure? A. A dirty condenser B. An overcharge of refrigerant C. A high heat load D. A restricted drier D. A restricted drier The blower wheel used by a direct drive blower will have an rpm that is: A. lower than the blower motor. B. higher than the blower motor. C. determined by the pully diameter of blower motor. D. the same as the blower motor. *D Two ninety degree short radius elbows are added to an air conditioner suction line. This charge could have what effect on the system? A. Suction line pressure drop will decrease with an increase of efficiency B. Suction line pressure drop will increase with a decrease of efficiency C. Suction line pressure drop will remain the same but efficiency will drop D. There will never be an effect on the system performance *D Electronic air cleaners can operate with internal voltages as high as: A. 120 volts. B. 240 volts. C. 500 volts. D. 5000 volts. D. 5000 volts. The lubricating oil primarily used with R-22 air conditioning compressors is: A. Polyolesters (POE). B. Mineral oil based.
C. Alkybenzenes. D. Polyalkylene Glycol (PAG). B. Mineral oil based. Thermostatic expansion valves meter refrigerant flow to a coil to maintain: A. superheated refrigerant leaving the coil. B. subcooled refrigerant leaving the coil. C. constant pressure in the coil. D. constant temperature in the coil. A. superheated refrigerant leaving the coil. Why do some electromechanical type thermostats require connections to both the hot side and common side of the low voltage transformer? A. The thermostat switches both sides of the line to all connected devices B. Display lights must be powered using both sides of the line C. All thermostats must be powered using both sides of the transformer secondary D. Thermostats with a heat anticipator must be powered using both sides of the line B. Display lights must be powered using both sides of the line How should a mercury bulb thermostat be disposed of? A. Return to the original equipment manufacturer B. Return to approved recycling facility C. Return to homeowner D. Dispose in a sealed container B. Return to approved recycling facility When a disc-type, close-on-rise pressure control is being used as a loss-of-charge limit control on the liquid-line has its setpoint drift lower: A. The condensing pressure will drop. B. The condensing pressure no longer will be regulated. C. The system is less likely to shut down as a result of a small leak. D. The system is more likely to shut down as a result of a small leak. *D Which of the following is a typical use of an outdoor ambient thermostat in a commercial split system air conditioner? A. Increase blower speed in high ambient
A. The blower, condenser fan, and the compressor all come on at the same time B. The condenser fan and compressor come on first. The blower cycles intermittently C. The compressor comes on first. The blower and condenser fan come on last D. The condenser fan and blower come on first. The compressor cycles as needed *A For indoor air quality purposes, the minimum horizontal distance between an economizer or fresh air intake and plumbing vent shall be: A. 3 feet. B. 5 feet. C. 10 feet. D. 15 feet.
What is the purpose of the grounding conductor? A. Personal and equipment protection B. Protect against motor overload C. Provide a neutral conductor D. To complete the circuit A. Personal and equipment protection According to generally accepted national codes, what is the smallest size pipe that can be used to carry condensate from the secondary drain pan? A. 3/8" nominal B. 1/2" nominal C. 3/4" nominal D. 1" nominal *C According to fire protection codes, when should fire dampers be used? A. In the air ducts of any light commercial installation with more than 2000 CFM B. In the air ducts of any light commercial installation with more than 400 CFM C. In any air duct that passes through all walls or partitions of light commercial installation D. In any air duct that passes through a two-hour fire rated wall or partition of a light commercial installation *D
Electronic air cleaners do not remove: A. airborne animal fur. B. odors. C. carpet fibers. D. dust and dirt. *B According to ANSI/ACCA Manual D, when balancing dampers are used, what is their preferred location in a duct system to reduce noise? A. In the last run of duct and close to the supply registers B. Near the trunk duct takeoff C. Halfway between the branch connections and the registers D. At the registers for ceiling supplies and at the branch connections for wall supplies *B Hard start kits are typically required on: A. systems with reciprocating compressors and thermostatic expansion valve metering devices. B. systems with reciprocating compressors and fixed orifice metering. C. any system where a crankcase heater is used. D. any system where a crankcase heater is not used. *A A delay on make relay delays load: A. from de-energizing for a fixed time period after cycle. B. from energizing for a fixed time period after cycle. C. from energizing for a fixed time period at the start of cycle. D. from de-energizing for a fixed time period at start of cycle. *B A delay on break relay delays load: A. from de-energizing for a fixed time period after cycle. B. from energizing for a fixed time period after cycle. C. from energizing for a fixed time period at the start of cycle. D. from de-energizing for a fixed time period at start of cycle. *C
