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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. A commercial customer calls on a 90
An undercharged system+insufficient airflow over the evaporator coil
'G' to 'C'
The system has been overcharged+The system has air trapped in the condenser
Technician A is correct

2. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
The external equalizer could be plugged
A plugged filter drier
A restricted metering device
Technician B

3. 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
It keeps a constant superheat in the evaporator
An open internal overload protector
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
The low-side pressure will decrease and the evaporator coil will be partially frosted

4. 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
A plugged filter drier
Clean the condenser coil
A sensing bulb improperly connected to the suction line

5. 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...
The external equalizer could be plugged
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Dirty condenser - bent condenser fins - and air recirculating over the condenser
('Y' and 'C') and ('G' and 'C')

6. 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
Short cycling and insufficient dehumidification
Technician B
A defective circuit breaker
Technician B

7. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
A plugged filter drier
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Evaporator and compressor
It would cause the low-side pressure to decrease

8. What are the symptoms of an air conditioning system that has a bad compressor discharge valve...
110-120
Low discharge pressure - high suction pressure - and low amp draw
Condenser fans operating during a low ambient condition and a low suction pressure
The sight glass is full of liquid+the sight glass is full of gas

9. When using a vapor-charged TXV bulb - it is necessary to have...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
An overcharged system
A sensing bulb improperly connected to the suction line
The sensing bulb at a lower temperature than the valve body

10. 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
Run with high head and high suction pressure
A bad thermostat
Low superheat
Technician A

11. The internal overload of an air conditioning compressor senses winding temperature and...
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
Current in the compressor circuit
A sensing bulb improperly connected to the suction line

12. A hard-start kit consists of...
A defective circuit breaker
A start capacitor and a solid-state relay
Short cycling and insufficient dehumidification
Technician B

13. A party-store owner tried to adjust the water valve on his water-cooled condensing unit - then he called for assistance from an HVAC/are service technician. It was found that when servicing the unit - the outlet water temperature was too low. Technic
The internal overload is opened
Lack of airflow
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Technician B

14. What is the purpose of a CPR valve...
A defective circuit breaker
It is used to control refrigerant pressure in the compressor crankcase
Low superheat
Technician B

15. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
('Y' and 'C') and ('G' and 'C')
The external equalizer could be plugged
A bad thermostat
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device

16. 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
'G' to 'C'
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Rise more than normal

17. 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
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
A start capacitor and a solid-state relay
Increases starting torque

18. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
It keeps a constant superheat in the evaporator
An uninsulated suction line and a restricted metering device
The discharge pressure increases and the amperage increases
The superheat will increase and the low-side pressure will decrease

19. Which of the following can cause excessive subcooling...
An overcharged system
Rise more than normal
High suction pressure and low superheat
An increase in low-side pressure

20. When a high-efficiency split air conditioning system has a plugged metering device - what symptoms might occur...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Dirty condenser - bent condenser fins - and air recirculating over the condenser
A vacuum test+oil traces around fittings+soap bubble solution
3 psig

21. A liquid-charged TXV bulb will...
An increase in suction pressure and an increase in discharge pressure
Always have some liquid present in the bulb and diaphragm
Technician B
Contains a solenoid coil and one or more sets of contacts

22. 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
Always have some liquid present in the bulb and diaphragm
Broken rings+broken valves+seized bearings
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

23. What are common methods that are used for leak-testing a system...
Low voltage and a faulty start relay
A vacuum test+oil traces around fittings+soap bubble solution
An increase in suction pressure and an increase in discharge pressure
Increases starting torque

24. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
An acid-core suction line drier
An increase in low-side pressure
An undercharge and low ambient conditions
Both technicians are incorrect

25. Superheat is found in an air conditioning system in the...
Flooding the condenser - cycling condenser fans - and dampering condenser air
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Evaporator and compressor

26. Insufficient airflow can be caused by...
A sensing bulb improperly connected to the suction line
An increase of air leakage from ductwork
Dirty condenser - bent condenser fins - and air recirculating over the condenser
A start capacitor and a solid-state relay

27. A customer calls with an insufficient cooling complaint. Upon arrival to the service call it is found that the outdoor condensing unit is operating - but the indoor blower is not in operation. Technician A says that it is possible that it is a bad fu
An uninsulated TXV sensing bulb
Broken rings+broken valves+seized bearings
Both technicians are incorrect
A defective circuit breaker

28. 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
Low superheat
It would cause the low-side pressure to decrease
Technician B
Low superheat

29. 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
Technician B
An undercharged system+insufficient airflow over the evaporator coil
An open internal overload protector
It would cause the low-side pressure to decrease

30. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
The superheat increases and the subcooling decreases
The sight glass is full of liquid+the sight glass is full of gas
An undercharge and low ambient conditions
110-120

31. A customer calls with an insufficient cooling complaint on a 90
Evaporator and compressor
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Short cycling and insufficient dehumidification
Technician B

32. 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
Technician B
3 psig
It keeps a constant superheat in the evaporator
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

33. What component is most often the cause of a start capacitor failure...
A start relay
Current in the compressor circuit
110-120
Contains a solenoid coil and one or more sets of contacts

34. Which of the following is a possible cause for a compressor to overheat...
A low refrigerant charge
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Both technicians are correct
Clean the condenser coil

35. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Technician B
20 to 30

36. 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
Technician B
An undercharge and low ambient conditions
An acid-core suction line drier
An increase in suction pressure and an increase in discharge pressure

37. 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
An increase in suction pressure and an increase in discharge pressure
Both technicians are correct
An increase in low-side pressure

38. What are two problems that can cause an air conditioning system to have an excessively high superheat...
Both technicians are correct
An uninsulated suction line and a restricted metering device
The internal overload is opened
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

39. What is the purpose of a CPR valve...
An open internal overload protector
It is used to control refrigerant pressure in the compressor crankcase
Condenser fans operating during a low ambient condition and a low suction pressure
Run with high head and high suction pressure

40. Which of the following problems can cause a decrease in a system's pressures and possible icing of the evaporator coil...
Contains a solenoid coil and one or more sets of contacts
It keeps a constant superheat in the evaporator
A missing air filter+improper rotation of the indoor blower+blower too small
Lack of airflow

41. Which of the following can cause excessive subcooling...
It keeps a constant superheat in the evaporator
An overcharged system
The sight glass is full of liquid+the sight glass is full of gas
3 psig

42. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
A restricted metering device
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
An undercharge and low ambient conditions
An uninsulated suction line and a restricted metering device

43. Which of the following can cause low superheat in a TXV system...
The discharge pressure increases and the amperage increases
Both technicians are correct
'G' to 'C'
An uninsulated TXV sensing bulb

44. 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
Low superheat
A plugged filter drier
Condenser fans operating during a low ambient condition and a low suction pressure

45. 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
Technician B
Whenever necessary
An increase in low-side pressure

46. Insufficient airflow can be caused by...
An undercharge and low ambient conditions
High suction pressure and low superheat
20 to 30
An increase of air leakage from ductwork

47. 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
Technician A is correct
'G' to 'C'
A bad thermostat
A dirty condenser - recirculation of condenser air - and a defective condenser fan

48. Air filters should be replaced...
High suction pressure and low superheat
Contains a solenoid coil and one or more sets of contacts
Whenever necessary
Run with high head and high suction pressure

49. 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
The system has been overcharged+The system has air trapped in the condenser
Technician B
Flooding the condenser - cycling condenser fans - and dampering condenser air
The superheat increases and the subcooling decreases

50. After a compressor motor has been severely burnt - What accessory must be added as an aid to rid the air conditioning system of acid...
Flooding the condenser - cycling condenser fans - and dampering condenser air
Whenever necessary
An acid-core suction line drier
An increase in low-side pressure

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NATE Air Conditioning Troubleshooting

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