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NATE Air Conditioning Troubleshooting

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
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. When testing an indoor blower control circuit and the cooling circuit on a fan center - what terminals should read 24 volts if the air conditioning system is in operation...

2. Insufficient airflow can be caused by...
An increase of air leakage from ductwork
Both technicians are correct
An open internal overload protector
An undercharged system+insufficient airflow over the evaporator coil

3. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
An overcharged system
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
An uninsulated suction line and a restricted metering device

4. What type of problems can be caused by an oversized air conditioning system...
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
Increases starting torque
Short cycling and insufficient dehumidification

5. The internal overload of an air conditioning compressor senses winding temperature and...
A start relay
Increases starting torque
Current in the compressor circuit
Technician B

6. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
An increase in suction pressure and an increase in discharge pressure
A sensing bulb improperly connected to the suction line
The superheat increases and the subcooling decreases
An overcharged system

7. Technician A says that to manually pump down an air conditioning system with a two-position service valve - the liquid line must be front-seated and the high- and low-side pressure will decrease to 0 psig when the pump-down is complete. Technician B
Low superheat
A defective circuit breaker
The sight glass is full of liquid+the sight glass is full of gas
Technician A is correct

8. What are two common symptoms of refrigerant leaks in an air conditioning system...
The external equalizer could be plugged
Partially frosted evaporator and high superheat
Low discharge pressure - high suction pressure - and low amp draw
An increase in low-side pressure

9. Which of the following can cause low superheat in a TXV system...
An uninsulated TXV sensing bulb
The internal overload is opened
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An acid-core suction line drier

10. 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
Broken rings+broken valves+seized bearings
Technician B
Whenever necessary
An increase in low-side pressure

11. 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 internal overload is opened
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
20 to 30
An undercharged system+insufficient airflow over the evaporator coil

12. Insufficient airflow can be caused by...
50-65
An uninsulated TXV sensing bulb
An increase of air leakage from ductwork
Technician B

13. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Clean the condenser coil
Lack of airflow
An overcharged system
Technician A is correct

14. What is the purpose of the TXV...
An undercharge and low ambient conditions
Bad compressor valve
It keeps a constant superheat in the evaporator
The external equalizer could be plugged

15. What is the purpose of an EPR valve...
Short cycling and insufficient dehumidification
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
A sensing bulb improperly connected to the suction line

16. 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
'G' to 'C'
An increase in low-side pressure
An open internal overload protector
Both technicians are incorrect

17. If 24 volts are present to the contactor coil on an air conditioning system and the condenser fan or compressor is inoperative - which of the following could be at fault...
A sensing bulb improperly connected to the suction line
A blown fuse
Both technicians are incorrect
Both technicians are correct

18. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
The oil pump pressure and the crankcase pressure
Technician B
A start relay
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

19. 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
The oil pump pressure and the crankcase pressure
Current in the compressor circuit
A bad thermostat
A sensing bulb improperly connected to the suction line

20. What is the common cause of a compressor burnout...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Technician B
Bad compressor valve
High suction pressure and low superheat

21. After a compressor motor has been severely burnt - What accessory must be added as an aid to rid the air conditioning system of acid...
('Y' and 'C') and ('G' and 'C')
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
An acid-core suction line drier

22. A compressor having tight bearings would cause the current value to...
The low-side pressure will decrease and the evaporator coil will be partially frosted
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
An acid-core suction line drier
Rise more than normal

23. Air filters should be replaced...
Whenever necessary
Technician B
Technician B
An overcharged system

24. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Lack of airflow
It is used to control refrigerant pressure in the compressor crankcase
Dirty condenser - bent condenser fins - and air recirculating over the condenser
An uninsulated suction line and a restricted metering device

25. The internal overload of an air conditioning compressor senses winding temperature and...
Current in the compressor circuit
Broken rings+broken valves+seized bearings
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
A start relay

26. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
Both technicians are correct
Run with high head and high suction pressure
20 to 30
It keeps a constant superheat in the evaporator

27. 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
It keeps a constant superheat in the evaporator
Evaporator and compressor
Flooding the condenser - cycling condenser fans - and dampering condenser air

28. 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
Both technicians are incorrect
Broken rings+broken valves+seized bearings
Technician B
Partially frosted evaporator and high superheat

29. A customer calls with an insufficient cooling complaint. Upon arrival to the service call it is found that the system is using are-22 with the high-side pressure at 290 psig and the low-side pressure at 85 psig. The ambient temperature is 85
Technician A
The superheat will increase and the low-side pressure will decrease
An undercharged system+insufficient airflow over the evaporator coil
The discharge pressure increases and the amperage increases

30. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Low discharge pressure - high suction pressure - and low amp draw
Rise more than normal
An increase of air leakage from ductwork
The sensing bulb at a lower temperature than the valve body

31. A system that is operating with a clear sight glass shows...
An increase in suction pressure and an increase in discharge pressure
High superheat and low discharge pressure
The sight glass is full of liquid+the sight glass is full of gas
Technician B

32. Which of the following could be the cause for a system's discharge and suction pressure being low...
Current in the compressor circuit
An undercharged system+insufficient airflow over the evaporator coil
A restricted metering device
Evaporator and compressor

33. A customer calls with an insufficient cooling complaint. Upon arrival to the service call it is found that the system is using are-22 with the high-side pressure at 290 psig and the low-side pressure at 85 psig. The ambient temperature is 85
Evaporator and compressor
Technician A
('Y' and 'C') and ('G' and 'C')
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

34. What three things can prevent an air conditioning system from releasing heat at the proper rate...
Broken rings+broken valves+seized bearings
Run with high head and high suction pressure
It keeps a constant superheat in the evaporator
A dirty condenser - recirculation of condenser air - and a defective condenser fan

35. 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...
High superheat and low discharge pressure
Technician A
Technician A is correct
Whenever necessary

36. A liquid-charged TXV bulb will...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Always have some liquid present in the bulb and diaphragm
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

37. A system that uses a thermal electric expansion valve...
A sensing bulb improperly connected to the suction line
Technician B
A low refrigerant charge
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

38. What are the operating pressures of an oil pressure safety switch...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
High suction pressure and low superheat
Clean the condenser coil
The oil pump pressure and the crankcase pressure

39. What are common methods that are used for leak-testing a system...
An overcharged system
A vacuum test+oil traces around fittings+soap bubble solution
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Always have some liquid present in the bulb and diaphragm

40. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
Technician B
Evaporator and compressor
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
It would cause the low-side pressure to decrease

41. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Broken rings+broken valves+seized bearings
Flooding the condenser - cycling condenser fans - and dampering condenser air
An undercharge and low ambient conditions
The oil pump pressure and the crankcase pressure

42. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
Short cycling and insufficient dehumidification
The low-side pressure will decrease and the evaporator coil will be partially frosted
Low discharge pressure - high suction pressure - and low amp draw
A sensing bulb improperly connected to the suction line

43. Which of the following can cause low superheat in a TXV system...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Run with high head and high suction pressure
An open internal overload protector
An uninsulated TXV sensing bulb

44. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Short cycling and insufficient dehumidification
Technician B
The internal overload is opened
An uninsulated suction line and a restricted metering device

45. A 220-volt 30-amp motor circuit keeps tripping the breaker after the motor is started. The starting amperage is 60 amps. When measuring the amperage of the circuit - This is drawn for a brief moment. After startup - the amperage drops to 22 amps and
A defective circuit breaker
The internal overload is opened
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Rise more than normal

46. 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
An acid-core suction line drier
110-120
Technician B
Technician A is correct

47. A commercial customer calls complaining that her rooftop air conditioning system is not operating. The technician arrives on the job and sets the thermostat to cooling - then notices that the indoor fan is not operating. The technician then sets the

48. If 24 volts are present to the contactor coil on an air conditioning system and the condenser fan or compressor is inoperative - which of the following could be at fault...
The superheat will increase and the low-side pressure will decrease
Technician B
Dirty condenser - bent condenser fins - and air recirculating over the condenser
A blown fuse

49. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
3 psig
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Low voltage and a faulty start relay
An uninsulated suction line and a restricted metering device

50. Air filters should be replaced...
Technician B
Whenever necessary
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Technician B