Residential Air Conditioning Systems Mechanic (313D) Certification Practice Exam

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• What does an ohm reading of 12 from R to ground in a hermetic compressor suggest?
• What is a possible reason for uncomfortable cooling in an air conditioning system that is appropriately charged and sized?
• How can you determine the type of refrigerant in a system?
• What happens to moisture in a refrigeration system if the evaporator is not properly charged?
• Can an A-coil contribute to furnace overheating?
• When replacing a single pole compressor contactor with a double pole, how should you connect an off-cycle self-regulating crankcase heater?
• In terms of airflow, what does CFM stand for?
• What type of influence does the bulb exert on a TXV valve?
• What effect does a zone damper that fails to open have in a heat pump cooling mode?
• If a water regulating valve for a condenser is jammed and too restrictive, what happens to the compressor amperage?
• What is the primary function of a TXV?
• What happens to the suction pressure when condenser air flow is poor?
• What happens to the compressor in reverse cycle heat pumps during the defrost cycle?
• What is the main substance found in Earth's atmosphere?
• Which component is primarily responsible for controlling humidity in an HVAC system?
• Which gas is considered the most dangerous to use for pressure testing in residential air conditioning?
• What material is typically used to braze dissimilar metals on a refrigerant system?
• What can lead to a higher compressor ratio in air conditioning systems?
• What purpose does the equalizer line serve on a TXV?
• Which three instruments are essential for checking the calibration of an enthalpy control on an economizer of a rooftop air conditioning unit?
• How can you adjust the TXV if you have too much head pressure?
• Low suction pressure in an air conditioning system can be caused by which factor?
• Which statement is true regarding the capabilities of relays?
• True or False: Due to heat compression, condensers must release more heat than evaporators can absorb.
• Which method is used to determine the approach of a cooling tower?
• What is the main purpose of the "Y" terminal in HVAC systems?
• During the installation of an air conditioning system, which voltage transformer is commonly addressed?
• What is the purpose of a crankcase heater?
• If capacitors of 20MFD@370VAC and 15MFD@370VAC are wired in series, what is the total capacitance?
• What function does the cooling anticipator serve?
• What is a probable cause of high suction pressure on a heat pump?
• Condensation on the suction line occurs when its temperature is:
• Which of the following statements is true regarding line temperatures?
• What causes the high head pressure switch to open on a water-cooled condenser unit?
• According to the first law of thermodynamics, what is true about heat as a form of energy?
• What is the purpose of a crankcase heater on a compressor?
• What is the likely issue if an R22 system has a suction pressure of 15 PSIG and exhibits a small amount of frost at the end of the cap tubes?
• Where should the vapor barrier be installed when constructing a walk-in freezer box?
• In an HVAC system, what does TXV stand for?
• Before installing the lineset insulation, what should be done to seal the ends of the lineset?
• What is the definition of recycle in HVAC systems?
• Which component is primarily responsible for regulating the flow of refrigerant in an R22 system using capillary tubes?
• What effect does a hard start kit have on an electric motor?
• What is used to confirm airflow through an evaporator coil in a correctly charged air conditioning system?
• What are the symptoms of an internal leak on a 4-way reversing valve?
• What should be primarily checked when installing an air conditioner on an old furnace?
• What is the required CFM for an A/C system per ton?
• What is the definition of electricity in terms of electron flow?
• What is the minimum required sleeve size when installing a 50 mm (2 in) nominal pipe with 38 mm (1.5 in) insulation through a concrete block wall?
• What indicates a problem with airflow in the condenser unit?
• What effect does dirty evaporator coils have on air conditioning performance?
• In commissioning a new secondary refrigerant system without an automatic bleed valve, what is the procedure to remove air?
• What type of refrigerant is typically used in residential units?
• What action should be taken if the evaporator coil is damaged?
• What is the purpose of reversing valves in air conditioning systems?
• In an R22 system, what would a high head pressure and low suction pressure combination potentially indicate?
• What drives the reversing valve to shift in a heat pump system?
• What does the "r" terminal provide in an HVAC system?
• What is the likely consequence of having an overcharge of refrigerant in an air conditioning system?
• If a fan has an 8" pulley turning at 850 RPM and the drive is 5", what is the motor RPM?
• What type of wiring configuration is common for a thermostat connected to an HVAC system?
• Most HVAC thermostats operate using voltage from:
• When checking for continuity in a circuit, what is a crucial first step?
• Hermetic compressor motors for residential air conditioning are generally classified as which type?
• What should be the amperage capacity of the breaker for a refrigerated fixture with a 208 V power supply and specific load ratings?
• How does atmospheric pressure influence the refrigeration cycle?
• Which component is unlikely to be present in a ground source heat pump?
• In hermetic compressors, when does the compressor draw refrigerant from the evaporator?
• What is typically the function of capillary tubes in an R22 refrigeration cycle?
• What is a common cause of condenser coil failure?
• Is it true that typical single phase induction motors have a start winding that disconnects shortly after startup?
• If the ambient temperature rises during an R22 system operation, what effect does it have on suction pressure?
• What does it indicate when the filter drier is half frosted up?
• Which instrument is used to measure wet bulb and dry bulb temperatures?
• What is the consequence of an uninsulated suction line?
• In a unit rating plate for an R22 TXV system with specific superheat and subcooling values, what is the first action to take if the system is running and has a suction pressure of 40 PSIG?
• How many ports are present on a reversing valve?
• What can excessive refrigerant in a system lead to?
• Which technique is commonly used to clean refrigerant before returning it to the HVAC system?
• What is the typical function of a voltmeter?
• What tool is used to de-burr copper tubing?
• What happens if the TXV is adjusted incorrectly?
• What happens to system pressure when a refrigerant leak occurs?
• What does proper superheat indicate about the operation of the system?
• What is one of the key functions of a fan/limit control?
• What is the maximum voltage rating for the capacitors mentioned?
• What visual clue indicates that you can now apply the filler alloy when using flux?
• In a 4 wire control system, which two terminals will have a jumper at the thermostat?
• What is the purpose of heat anticipators in heating systems?
• As humidity rises, what happens to the air temperature difference across an evaporator coil?
• What must be verified before replacing the electronic control board if the onboard diagnostics fault is incorrect?
• What would be the minimum VA requirements for a 24 VAC transformer powering four terminal electric expansion valves each with a resistance of 150 ohms?
• How can you reverse the rotation on a CSR motor?
• What should you do if the condenser coil is damaged?
• What might cause low static pressure in a zoned HVAC system?
• In troubleshooting HVAC equipment, what is often the first step a technician takes?
• What charge do electrons possess?
• If the indoor dry bulb is 73°F and the wet bulb is 68°F, what might be causing discomfort for the customer?
• If a 3-inch drive pulley is spinning at 1720 RPM, what is the RPM of an 8-inch pulley?
• Which of the following factors can lead to increased suction pressure in a refrigeration system?
• To increase superheat on a TXV system, you should turn the spring:
• During the heat pump defrost cycle, how is the cooling cycle modified?
• Which tool is commonly used to expand copper tubing?
• What happens to a circuit when a fuse breaks?
• When is the "Y" terminal energized in an HVAC system?
• Which component would you not typically find in an outdoor unit of an air source heat pump?
• What maximum fill level should not be exceeded when filling a cylinder with refrigerant at ambient temperature of 70°F?
• At what temperature does copper tubing glow with a red/brass color?
• What is a common symptom of poor condenser airflow?
• What type of gas is commonly used to pressure test a refrigeration system?
• If you have a 2 ton evaporator and a 3 ton condenser, what is the recommended action?
• Which type of relay typically has multiple poles?
• What role does a thermal expansion valve play in a refrigeration system?
• If the indoor temperature is 74°F DB and 62°F WB, what does this suggest about moisture in the air?
• How does the outdoor air temperature affect an air-source heat pump in heating mode?
• What is the minimum required hole size to accommodate a 30 mm (1 in) O.D. copper pipe with a 20 mm (3/4 in) insulation?
• What happens when the contactor is energized and there is 220V on the input side but only 110V on the load side?
• Why is a fan control center added to an older furnace when installing a new air conditioner?
• What is the approximate R22 liquid pressure at the metering device inlet if the liquid line is raised 50ft and the pressure at the condenser outlet is 200PSIG?
• In an R22 system with an outdoor dry bulb temperature of 80°F and a wet bulb temperature of 71°F, what would be the typical suction and head pressures?
• How does reversing the leads at the start winding affect a CSR motor?
• What can be a symptom of inadequate air flow in an air conditioning system?
• What does the equalizer line on a TXV connect to?
• During maintenance calls, if the air system is at design conditions yet compression ratios are decreasing, what is likely the cause?
• What might cause low suction pressure in a refrigeration system?
• If a pitot tube connected to an inclined manometer reads 0.2" water column, what is the calculated air velocity?
• What should be checked if a blower is running over the service factor amperage draw on a motor?
• What does a hydrometer measure?
• A mechanically seized compressor draws what current type?
• What happens to an air source heat pump unit when the defrost cycle is activated?
• Which component is typically reviewed when troubleshooting high compressor amperage in a refrigeration system?
• What temperature is indicative of normal operational conditions for an R22 air conditioning system?
• What do motors primarily convert into movement?
• When does volumetric efficiency increase in an air conditioning system?
• What can excessive load on the evaporator lead to?
• In a grounded circuit, what level of resistance should you expect?
• To ensure proper evacuation, R22 systems should be evacuated down to:
• How should a load be lifted with a wrap-around sling if crushing of the load is a major concern?
• During which phase does the compressor in a heat pump operate to absorb heat from the evaporator?
• Do clogged air filters have the potential to cause liquid refrigerant to flow to the compressor?
• When diagnosing airflow issues in an AC system, which component may need inspection first?
• During a diagnostic check, finding both high head pressure and low suction pressure in an R22 system likely requires which type of action?
• What is the principal function of an expansion tank in a hot water system?
• What is a common symptom of a plugged filter drier?
• Where is the line from the external equalizer typically installed?
• What could be the reason for low discharge static pressure on a new split system that is properly charged?
• What could be a cause of an irritating ozone smell from an electronic air cleaner?
• What type of influence does the spring exert on a TXV valve?
• What is the purpose of a resistor used on a capacitor?
• What happens to power loss in a fan motor?
• What vacuum measurement indicates a good vacuum level in a refrigeration system?
• What can cause liquid refrigerant to accumulate in the condenser?
• What is the requirement for condensate drain lines?
• Is it acceptable to install an "A" coil in the return air plenum of a furnace?
• If a technician notices high head pressure during a routine check, what might be a possible cause?
• If a metering device is too permissive, what is the likely result on head pressure?
• When troubleshooting, what does a low refrigerant level typically indicate?
• What external factor can break down CFCs?
• What is the main difference between a Heat Recovery Ventilator (HRV) and an Energy Recovery Ventilator (ERV)?
• What reading would indicate a good clean system when testing compressor motor windings with a megger?
• What is the effect of a dirty condenser in a capillary tube system on a bar refrigerator?
• What components are changed when replacing a burnt compressor?
• What two values are required to measure relative humidity?
• What should you check next after changing the pulley on a blower motor from 3 1/4" to 4"?
• Which T-stat terminals are used when employing a 4-wire setup?
• What is the total capacitance of two capacitors in parallel if the first is 15MFD at 370VAC and the second is 20MFD at 440VAC?
• What is the primary function of a Heat Recovery Ventilator (HRV)?
• What is one critical maintenance step for air conditioning systems regarding the TXV?
• If you have a precharged line set good for 15 feet and the total length is 50 feet, how much refrigerant is required at 0.6 oz per foot?
• What is the consequence of inadequate refrigerant flow in a heat pump system?
• What is the total capacitance if capacitors of 20MFD@370VAC and 15MFD@370VAC are wired in parallel?
• How often should air filters in air conditioning systems be checked and replaced?
• Which of the following can cause an evaporator to freeze up?
• If the pressure differential across the circulating pump is 21.65 PSI, how many meters (feet) of head can the pump lift?
• What is the role of a refrigerant in an air conditioning system?
• What key component may need installation when retrofitting an air conditioning system to an older furnace?
• What should be done if the head pressure in an R22 system is significantly high during operation?
• What type of copper tubing is required for refrigeration systems?
• When fresh air is brought in for ventilation, what effect does it have during summer?
• Which condition can cause the compressor RLA to increase?
• What would likely cause a time-initiated temperature-terminated defrost to run full time during light coil frosting?
• What type of influence does the evaporator pressure exert on the valve in a TXV?
• What might cause high superheat readings in a thermal expansion valve (TXV) system?
• What does the term "superheat" refer to in HVAC systems?
• What is the primary symptom of a clogged cap tube in an air conditioning system?
• What is the absorption of heat in the evaporator dependent upon?
• Which of the following components is crucial for starting an AC compressor?
• What is typically the voltage supplied to the "C" terminal?
• What configuration is used for a heat pump installation added onto an existing system?
• Which cooling coil configuration is selected for maximum dehumidification?
• What is the best way to test the limit switch on a furnace after installing a fan control center?
• What maintenance task is crucial for preventing the overheating of a hermetic compressor?
• When frost is observed at the end of the cap tubes in an R22 system, what does it typically suggest?
• Which statement is accurate about conventional fan/limit controls?
• What pressure difference indicates a potentially faulty compressor in an HVAC system?
• What is unique about the "C" terminal in HVAC systems?
• Which factor primarily affects the boiling point of water?
• Where should a liquid line drier be installed in a refrigeration system?
• What impact does a TXV stuck nearly shut have on a refrigeration system?
• What should you expect in terms of resistance in an open circuit?
• What voltage and phase is typically found in most residential breaker panels?
• What does the wet bulb temperature primarily indicate in an indoor environment?
• Which factors are essential for assessing the performance of an air conditioning system?
• If the interconnecting line set exceeds the standard length, what should be done?
• When evaluating the frost at the capillary tubes, what action should be taken if it is determined to be a blockage?
• What is the function of the middle tab on a dial of a conventional fan/limit control?
• What should be installed if a system has a non-bleed type TXV?
• What kind of influence does the high side pressure exert on the valve in a TXV?
• If a reversing valve has an internal leak, what potential issues can arise?
• Which of the following is becoming the industry-accepted replacement for R22?
• What role does a filter drier play in a refrigeration system?
• In what situation would you consider upgrading a TXV?
• What corrective action should be taken when a zone damper actuator motor is seized?
• Fuses in electrical circuits are designed to function as what?
• What type of electrical breaker is typically used for a residential gas furnace?
• Which control can effectively solve low head pressure problems?
• What do potential relay contacts open in response to?