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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. What are three methods for controlling a system's high-side pressure during low ambient conditions...
The oil pump pressure and the crankcase pressure
Technician B
An uninsulated TXV sensing bulb
Flooding the condenser - cycling condenser fans - and dampering condenser air

2. What are the symptoms of a TXV air conditioning system if it has lost its charge...
The sight glass is full of liquid+the sight glass is full of gas
Technician B
The superheat will increase and the low-side pressure will decrease
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

3. 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
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Technician B
Both technicians are incorrect
'G' to 'C'

4. Which of the following is a possible cause for a compressor to overheat...
Broken rings+broken valves+seized bearings
The superheat increases and the subcooling decreases
A low refrigerant charge
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

5. A system that is being serviced has been evacuated down to 500 microns. When the gauges are closed and the vacuum pump is turned off - the pressure starts to increase and stops at 1000 microns. Technician A says that the system has a leak and needs t
Flooding the condenser - cycling condenser fans - and dampering condenser air
It is used to control refrigerant pressure in the compressor crankcase
The sensing bulb at a lower temperature than the valve body
Technician B

6. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
3 psig
The superheat will increase and the low-side pressure will decrease
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
A missing air filter+improper rotation of the indoor blower+blower too small

7. A liquid-charged TXV bulb will...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Technician B
A missing air filter+improper rotation of the indoor blower+blower too small
Always have some liquid present in the bulb and diaphragm

8. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
'G' to 'C'
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A defective circuit breaker
Evaporator and compressor

9. What are common methods that are used for leak-testing a system...
A vacuum test+oil traces around fittings+soap bubble solution
Low superheat
Current in the compressor circuit
The external equalizer could be plugged

10. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Lack of airflow
20 to 30
Both technicians are incorrect
Bad compressor valve

11. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
Increases starting torque
An increase in suction pressure and an increase in discharge pressure
110-120
A blown fuse

12. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
Technician B
Run with high head and high suction pressure
It would cause the low-side pressure to decrease
Technician B

13. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Short cycling and insufficient dehumidification
An overcharged system
Clean the condenser coil
The oil pump pressure and the crankcase pressure

14. 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
The sight glass is full of liquid+the sight glass is full of gas
The superheat increases and the subcooling decreases
An uninsulated TXV sensing bulb
Broken rings+broken valves+seized bearings

15. Which of the following is a common cause of an excessively low superheat on a TXV system...
A bad thermostat
An uninsulated suction line and a restricted metering device
A sensing bulb improperly connected to the suction line
A dirty condenser - recirculation of condenser air - and a defective condenser fan

16. Air filters should be replaced...
Technician B
Whenever necessary
The internal overload is opened
An increase of air leakage from ductwork

17. A commercial customer calls on a 90
An overcharged system
The system has been overcharged+The system has air trapped in the condenser
A missing air filter+improper rotation of the indoor blower+blower too small
('Y' and 'C') and ('G' and 'C')

18. Which of the following can cause low superheat in a TXV system...
A plugged filter drier
20 to 30
An open internal overload protector
An uninsulated TXV sensing bulb

19. A compressor having tight bearings would cause the current value to...
Short cycling and insufficient dehumidification
Rise more than normal
A start relay
Bad compressor valve

20. 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...
('Y' and 'C') and ('G' and 'C')
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Rise more than normal
High superheat and low discharge pressure

21. What is the common cause of a compressor burnout...
Lack of airflow
A vacuum test+oil traces around fittings+soap bubble solution
A start capacitor and a solid-state relay
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

22. 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...

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23. 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

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24. The best description of a relay would be...
Contains a solenoid coil and one or more sets of contacts
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
The system has been overcharged+The system has air trapped in the condenser
'G' to 'C'

25. 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
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A sensing bulb improperly connected to the suction line
Both technicians are incorrect

26. A hard-start kit consists of...
It keeps a constant superheat in the evaporator
A start capacitor and a solid-state relay
It would cause the low-side pressure to decrease
The low-side pressure will decrease and the evaporator coil will be partially frosted

27. Insufficient airflow can be caused by...
The low-side pressure will decrease and the evaporator coil will be partially frosted
An increase of air leakage from ductwork
Low discharge pressure - high suction pressure - and low amp draw
Technician A

28. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Condenser fans operating during a low ambient condition and a low suction pressure
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Increases starting torque
Dirty condenser - bent condenser fins - and air recirculating over the condenser

29. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
110-120
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
110-120
An overcharged system

30. 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
Bad compressor valve
An undercharge and low ambient conditions
Technician B
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

31. What problem can cause an increase of discharge pressure and an increase of suction pressure...
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Technician B
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
An overcharged system

32. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Technician B
The superheat increases and the subcooling decreases
Technician B

33. What are two common symptoms of a rooftop air conditioning system that operates with a reverse-acting high-pressure control stuck in the closed position...
An overcharged system
The sensing bulb at a lower temperature than the valve body
Condenser fans operating during a low ambient condition and a low suction pressure
High suction pressure and low superheat

34. A system that is operating with a clear sight glass shows...
An increase in suction pressure and an increase in discharge pressure
The superheat will increase and the low-side pressure will decrease
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
The sight glass is full of liquid+the sight glass is full of gas

35. The internal overload of an air conditioning compressor senses winding temperature and...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Lack of airflow
Current in the compressor circuit
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure

36. What causes the automatic expansion valve to close...
An increase in low-side pressure
Rise more than normal
Rise more than normal
The superheat increases and the subcooling decreases

37. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
Lack of airflow
Short cycling and insufficient dehumidification
Clean the condenser coil
Technician A

38. A hard-start kit consists of...
A vacuum test+oil traces around fittings+soap bubble solution
Both technicians are incorrect
A start capacitor and a solid-state relay
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

39. 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...
A bad thermostat
An increase in low-side pressure
High superheat and low discharge pressure
Contains a solenoid coil and one or more sets of contacts

40. What are two problems that can cause an air conditioning system to have an excessively high superheat...
A vacuum test+oil traces around fittings+soap bubble solution
An uninsulated suction line and a restricted metering device
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Increases starting torque

41. Which of the following could be the cause for a system's discharge and suction pressure being low...
The superheat increases and the subcooling decreases
A restricted metering device
'G' to 'C'
An open internal overload protector

42. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
The superheat increases and the subcooling decreases
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
A missing air filter+improper rotation of the indoor blower+blower too small

43. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
The low-side pressure will decrease and the evaporator coil will be partially frosted
110-120
Technician B
An overcharged system

44. A customer calls with an insufficient cooling complaint on a 90
An undercharge and low ambient conditions
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Condenser fans operating during a low ambient condition and a low suction pressure
Technician B

45. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
A plugged filter drier
A low refrigerant charge
The internal overload is opened
A blown fuse

46. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
Technician B
Bad compressor valve
The discharge pressure increases and the amperage increases
A defective circuit breaker

47. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
The sight glass is full of liquid+the sight glass is full of gas
The sight glass is full of liquid+the sight glass is full of gas
Technician A is correct
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

48. 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
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Broken rings+broken valves+seized bearings
An acid-core suction line drier
It is used to control refrigerant pressure in the compressor crankcase

49. Which of the following is a possible cause for a compressor to overheat...
Technician B
Low voltage and a faulty start relay
A bad thermostat
A low refrigerant charge

50. What is the purpose of an EPR valve...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
It is used to control refrigerant pressure in the compressor crankcase
An undercharge and low ambient conditions
Technician B