NATE AC Service Certification QUESTIONS WITH COMPLETE 100% VERIFIED SOLUTIONS 2024/2025, Exams of Applied Mechanics

Download NATE AC Service Certification QUESTIONS WITH COMPLETE 100% VERIFIED SOLUTIONS 2024/2025 and more Exams Applied Mechanics in PDF only on Docsity! NATE AC Service Certification QUESTIONS WITH COMPLETE 100% VERIFIED SOLUTIONS 2024/2025 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 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: A. humidity problems. B. compressor overheating. C. restricted liquid line drier D. condenser fan motor overheating. A. humidity problems. A technician finds a R-410A system with the following: *Suction pressure is 105 psi *Suction line temperature is 75degF *Recommended superheat is 20degF This indicates the system: A. is overcharged. B. has excess airflow C. is undercharged. D. has low airflow C. is undercharged. What effect does overcharging have on subcooling? A. It depends on which type of refrigerant is used B. It increases it C. It decreases it D. It depends on the metering device used *D It depends on the metering device used When an air conditioner with a thermostatic expansion valve installed is overcharged, the excess charge should be removed by recovering some charge and checking: A. system pressures. B. superheat. C. subcooling. D. head pressure. *C. subcooling With an R-410A condensing pressure of 397 psig and a liquid line temperature of 108degF, what is the subcooling temperature? A. 36degF B. 24degF 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. 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 #49 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 * The continuity through a de-energized relay coil is checked by measuring: A. volts. B. amps. C. ohms. D. watts. C. ohms. When replacing a failed R-22 condensing unit with a new R-410A condensing unit: A. existing R-22 evaporator must be replaced. B. suction line must be increased one pipe size. C. suction line insulation must be 3/4" D. existing R-22 evaporator can be reused. A. existing R-22 evaporator must be replaced. Which of the following should be done to reduce vibration noise transmission in sheet metal ductwork? A. Decrease fan speed to boost CFM B. Rigidly anchor ductwork to the structure C. Add isolation collars D. Externally insulate both supply and return ductwork *C What is the recommended maximum external static pressure used for heating and cooling equipment with blowers for 5 tons of cooling or less (excluding high velocity)? A. 1.0 IWC B. 0.5 IWC C. 0.3 IWC D. 0.1 IWC D. 0.1 IWC How would the technician check a three phase blower motor to determine that it is rotating in the proper direction? A. Start the motor briefly using the disconnect and verify proper rotation B. Check the direction in which the blower vanes are sloped A. Two stage thermostat What is the effect on supply airflow using a PSC blower motor when adding a ducted return to a previously non-ducted return system? A. Airflow will be decreased. B. Airflow will be increased. C. Airflow will be essentially the same. D. Airflow will be decreased during heating only. *B When a split system air conditioner has a counterflow air handler, what are the best locations for return air grilles? A. In the floor B. On a sidewall next to the floor C. On a sidewall next to the ceiling D. So that the air flow is towards the supply grilles *C Most safety controls are wired in: A. parallel with the load. B. parallel with each other. C. series with the load. D. the common leg of the load. C. series with the load. Which of the following best describes the beginning of the sequence of operation of a split system air conditioner? A. Room temperature falls below setpoint, compressor and fan controls are energized B. Room temperature rises above setpoint, compressor and fan controls are energized C. Room temperature rises above setpoint, only the indoor fan control is control is energized D. Room temperature falls below setpoint, only the compressor control is energized *B Describe the air flow path of an outdoor pull-through coil. A. Air moves from the outside to the inside of the coil B. Air moves from the inside to the outside of the coil 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 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 When setting the indoor blower speed on an air conditioner, what is the recommended CFM of airflow per ton of cooling? A. 250 - 325 CFM B. 350 - 450 CFM C. 475 - 550 CFM D. 575 - 650 CFM B. 350 - 450 CFM The slab of a packaged air conditioner at grade level should be: A. up against the structure to provide added support. B. on a frame attached to the structure to improve service access. C. where it can be bonded to the structure to prevent sinking of the slab. D. isolated from the structure to minimize noise transmission. *D What precautions need to be taken with packaged AC system with ductwork installed outside? A. The duct must be sized with .2 friction rate B. Elbows must have turning vanes C. It must have seismic bracing D. It must be insulated and weatherproofed *D What do the initials "S.E.E.R." represent? A. Summer Energy Efficiency Rating B. Seasonal Energy Efficiency Ratio C. Supplementary Energy Efficiency Rating D. Summer Energy Efficiency Ratio B. Seasonal Energy Efficiency Ratio Which of the following is a benefit in using a properly sized 4" pleated media filter compared to a 1" fiberglass air filter? A. Equipment efficiency will be cleaned and reused B. The media filter can be cleaned and reused C. Indoor air quality will be improved D. Removes odors and particles *C What does the minimum circuit ampacity (MCA) listed on the dataplate is used to determine the: A. size of the branch circuit conductors that supply the equipment. B. measured amp draw of the equipment. C. maximum fuse or circuit breaker size. D. electric power in watts used by the equipment. A. size of the branch circuit conductors that supply the equipment.