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NATE Air Conditioning Troubleshooting

Instructions:

Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
Technician B
Low voltage and a faulty start relay
A plugged filter drier
A bad thermostat

2. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Low discharge pressure - high suction pressure - and low amp draw
Run with high head and high suction pressure
It is used to control refrigerant pressure in the compressor crankcase

3. A hard-start kit for an air conditioning system...
Increases starting torque
Low superheat
Technician B
The internal overload is opened

4. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Bad compressor valve
An overcharged system
Low discharge pressure - high suction pressure - and low amp draw
The oil pump pressure and the crankcase pressure

5. Which of the following is a common cause of an excessively low superheat on a TXV system...
Technician B
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Technician A
A sensing bulb improperly connected to the suction line

6. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
Broken rings+broken valves+seized bearings
'G' to 'C'
High suction pressure and low superheat
An overcharged system

7. What are common methods that are used for leak-testing a system...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
An uninsulated TXV sensing bulb
20 to 30
A vacuum test+oil traces around fittings+soap bubble solution

8. What are two common symptoms of refrigerant leaks in an air conditioning system...
Partially frosted evaporator and high superheat
Short cycling and insufficient dehumidification
Broken rings+broken valves+seized bearings
High superheat and low discharge pressure

9. Technician A says that if you connect 208 volts to the primary side of a 240-volt/ 24-volt transformer - the transformer will burn out. Technician B says that if you connect 208 volts to the primary side of a 240-volt/24-volt transformer - the contro
Technician B
20 to 30
Short cycling and insufficient dehumidification
3 psig

10. What problem can cause an increase of discharge pressure and an increase of suction pressure...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
An overcharged system
A vacuum test+oil traces around fittings+soap bubble solution
Technician B

11. Which of the following is a possible cause for a compressor to overheat...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The low-side pressure will decrease and the evaporator coil will be partially frosted
A low refrigerant charge
Technician B

12. What are two common symptoms of refrigerant leaks in an air conditioning system...
Partially frosted evaporator and high superheat
A start capacitor and a solid-state relay
Condenser fans operating during a low ambient condition and a low suction pressure
Broken rings+broken valves+seized bearings

13. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
Condenser fans operating during a low ambient condition and a low suction pressure
An undercharge and low ambient conditions
A missing air filter+improper rotation of the indoor blower+blower too small
Whenever necessary

14. Which of the following is a common cause of an excessively low superheat on a TXV system...
A start capacitor and a solid-state relay
A sensing bulb improperly connected to the suction line
An overcharged system
A blown fuse

15. A system that is operating with a clear sight glass shows...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The sight glass is full of liquid+the sight glass is full of gas
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

16. The temperature range of the suction line from an air conditioning system should be...
A sensing bulb improperly connected to the suction line
50-65
'G' to 'C'
Both technicians are correct

17. The best description of a relay would be...
An increase of air leakage from ductwork
Partially frosted evaporator and high superheat
Increases starting torque
Contains a solenoid coil and one or more sets of contacts

18. A customer calls and says that her air conditioning system is not cooling properly. Upon arrival - a technician notices that the suction line and compressor have frost buildup. Technician A says that the problem is probably a low charge. Technician B
Technician B
Low voltage and a faulty start relay
An acid-core suction line drier
The superheat increases and the subcooling decreases

19. Which of the following will cause excessive discharge pressures on an air conditioning system...
Both technicians are incorrect
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Low superheat
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

20. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
('Y' and 'C') and ('G' and 'C')
Broken rings+broken valves+seized bearings
Evaporator and compressor
It would cause the low-side pressure to decrease

21. What is the purpose of a CPR valve...
Low superheat
It is used to control refrigerant pressure in the compressor crankcase
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

22. When troubleshooting a split-system air conditioner - it is found that the compressor motor is humming but not starting. Technician A says that it could be an open internal overload protector. Technician B says that it could be a blown fuse. Which te
An undercharged system+insufficient airflow over the evaporator coil
Technician B
Both technicians are incorrect
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

23. A compressor motor starts and operates for a short period of time and cycles on the external overload protector. What are two possible problems that could cause this...
Low voltage and a faulty start relay
An overcharged system
Both technicians are correct
An undercharge and low ambient conditions

24. After a compressor motor has been severely burnt - What accessory must be added as an aid to rid the air conditioning system of acid...
Run with high head and high suction pressure
An acid-core suction line drier
High superheat and low discharge pressure
110-120

25. A customer calls and says that her air conditioning system is not cooling properly. Upon arrival - a technician notices that the suction line and compressor have frost buildup. Technician A says that the problem is probably a low charge. Technician B
The superheat will increase and the low-side pressure will decrease
Technician B
High suction pressure and low superheat
An increase of air leakage from ductwork

26. What causes the automatic expansion valve to close...
110-120
A vacuum test+oil traces around fittings+soap bubble solution
An increase in low-side pressure
Rise more than normal

27. If a rooftop air conditioning system does not have any means of low ambient protection - what will be two symptoms of the system when operating under a low ambient condition...
It keeps a constant superheat in the evaporator
Low superheat
High superheat and low discharge pressure
'G' to 'C'

28. What is the purpose of an EPR valve...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A bad thermostat
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
The sensing bulb at a lower temperature than the valve body

29. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
Condenser fans operating during a low ambient condition and a low suction pressure
Lack of airflow
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A start relay

30. What is the purpose of the TXV...
It keeps a constant superheat in the evaporator
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
A defective circuit breaker
A restricted metering device

31. A customer calls and complains that her high-efficiency air conditioning system is operating - but is not cooling properly. Further investigation shows that the system is using a TXV type of metering device. A subcooling check shows that the system a
Whenever necessary
An overcharged system
The external equalizer could be plugged
Both technicians are correct

32. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
The superheat increases and the subcooling decreases
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Broken rings+broken valves+seized bearings
The low-side pressure will decrease and the evaporator coil will be partially frosted

33. A technician arrives on the job and the customer complains that there is no cooling on his rooftop unit. Troubleshooting the system - the technician finds that the compressor is faulty. He notices that there is another faulty compressor laying next t
A sensing bulb improperly connected to the suction line
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Broken rings+broken valves+seized bearings
An uninsulated TXV sensing bulb

34. A customer calls to complain that his central air conditioning system is not cooling properly. The technician arrives on the job. He or she notices that the indoor blower has adequate airflow and the outdoor condenser fan is operating - but the compr
'G' to 'C'
An open internal overload protector
Both technicians are correct
An uninsulated TXV sensing bulb

35. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Technician B
A vacuum test+oil traces around fittings+soap bubble solution
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

36. An air conditioning system that uses a fan center has an inoperable indoor blower. When the thermostat is set for cooling and dialed below room temperature - a test with the voltmeter shows that there is 24 volts across terminals 'are' and 'G' at the
Technician A
A bad thermostat
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Both technicians are correct

37. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Bad compressor valve
Low voltage and a faulty start relay
A bad thermostat
('Y' and 'C') and ('G' and 'C')

38. A customer calls and complains that his air conditioning system is not operating properly. It is noticed that the compressor is not operating. A check on the run capacitor shows that there is 33 uf and the rating on the capacitor is 40 uf. Technician
Technician B
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
The low-side pressure will decrease and the evaporator coil will be partially frosted

39. The technician observes that the compressor is not operating. The compressor windings read 5 ohms start to run - run to common is opened - and start to common is opened. The technician concludes that...
The low-side pressure will decrease and the evaporator coil will be partially frosted
The internal overload is opened
Technician B
Low discharge pressure - high suction pressure - and low amp draw

40. The best description of a relay would be...
The sensing bulb at a lower temperature than the valve body
High suction pressure and low superheat
Contains a solenoid coil and one or more sets of contacts
A restricted metering device

41. A customer who owns a split air conditioning system complains that his system has been running but his house doesn't seem to be cooling properly. When the service technician arrives on the job - he or she finds that the indoor blower is operating and
Technician A
Whenever necessary
Clean the condenser coil
3 psig

42. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Flooding the condenser - cycling condenser fans - and dampering condenser air
Technician A
Contains a solenoid coil and one or more sets of contacts
An uninsulated TXV sensing bulb

43. Technician A says ' When charging a system using the superheat method - adding refrigerant to the system will increase the superheat.' Technician B says 'When charging a system using the superheat method - adding refrigerant will decrease the superhe
It is used to control refrigerant pressure in the compressor crankcase
An open internal overload protector
Current in the compressor circuit
Technician B

44. Which of the following could be the cause for a system's discharge and suction pressure being low...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Technician B
A restricted metering device

45. What type of problems can be caused by an oversized air conditioning system...
Short cycling and insufficient dehumidification
Low superheat
An increase of air leakage from ductwork
Technician B

46. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
Lack of airflow
The low-side pressure will decrease and the evaporator coil will be partially frosted
20 to 30
A dirty condenser - recirculation of condenser air - and a defective condenser fan

47. When troubleshooting a split-system air conditioner - it is found that the compressor motor is humming but not starting. Technician A says that it could be an open internal overload protector. Technician B says that it could be a blown fuse. Which te
Both technicians are incorrect
Technician B
It keeps a constant superheat in the evaporator
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

48. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
Bad compressor valve
A dirty condenser - recirculation of condenser air - and a defective condenser fan
110-120
The sight glass is full of liquid+the sight glass is full of gas

49. A liquid-charged TXV bulb will...
It would cause the low-side pressure to decrease
A missing air filter+improper rotation of the indoor blower+blower too small
A start capacitor and a solid-state relay
Always have some liquid present in the bulb and diaphragm

50. What are the operating pressures of an oil pressure safety switch...
'G' to 'C'
The oil pump pressure and the crankcase pressure
A sensing bulb improperly connected to the suction line
Technician A is correct

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NATE Air Conditioning Troubleshooting

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