Test your basic knowledge |

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. Air filters should be replaced...
An undercharged system+insufficient airflow over the evaporator coil
A start capacitor and a solid-state relay
Whenever necessary
An uninsulated suction line and a restricted metering device

2. A system that uses a thermal electric expansion valve...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Run with high head and high suction pressure
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

3. A liquid-charged TXV bulb will...
The sensing bulb at a lower temperature than the valve body
It keeps a constant superheat in the evaporator
Always have some liquid present in the bulb and diaphragm
Condenser fans operating during a low ambient condition and a low suction pressure

4. Which of the following will cause excessive discharge pressures on an air conditioning system...
An overcharged system
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The oil pump pressure and the crankcase pressure
110-120

5. The temperature range of the suction line from an air conditioning system should be...
An increase in suction pressure and an increase in discharge pressure
An acid-core suction line drier
An uninsulated TXV sensing bulb
50-65

6. 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
Technician B
The discharge pressure increases and the amperage increases
'G' to 'C'
A start relay

7. What causes the automatic expansion valve to close...
An increase in low-side pressure
The oil pump pressure and the crankcase pressure
Technician B
The sensing bulb at a lower temperature than the valve body

8. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
An overcharged system
The superheat increases and the subcooling decreases
The superheat increases and the subcooling decreases
It would cause the low-side pressure to decrease

9. Superheat is found in an air conditioning system in the...
Evaporator and compressor
The system has been overcharged+The system has air trapped in the condenser
An uninsulated TXV sensing bulb
A blown fuse

10. Which of the following can cause excessive subcooling...
Always have some liquid present in the bulb and diaphragm
The internal overload is opened
An overcharged system
A restricted metering device

11. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
An increase of air leakage from ductwork
An open internal overload protector
Technician B

12. What problem or problems can cause low discharge and suction pressure...
High suction pressure and low superheat
Dirty condenser - bent condenser fins - and air recirculating over the condenser
An undercharged system+insufficient airflow over the evaporator coil
Current in the compressor circuit

13. What are the operating pressures of an oil pressure safety switch...
Both technicians are incorrect
A plugged filter drier
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
The oil pump pressure and the crankcase pressure

14. 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
Both technicians are incorrect
The sight glass is full of liquid+the sight glass is full of gas
Technician B
Low superheat

15. What are two problems that can cause an air conditioning system to have an excessively high superheat...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
The discharge pressure increases and the amperage increases
An uninsulated suction line and a restricted metering device

16. A hard-start kit consists of...
Technician B
Bad compressor valve
A start capacitor and a solid-state relay
The discharge pressure increases and the amperage increases

17. What are the symptoms of an air conditioning system that has a low charge...
Technician B
'G' to 'C'
The low-side pressure will decrease and the evaporator coil will be partially frosted
110-120

18. 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 uninsulated suction line and a restricted metering device
Both technicians are incorrect
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Condenser fans operating during a low ambient condition and a low suction pressure

19. Which of the following is a possible cause for a compressor to overheat...
The sight glass is full of liquid+the sight glass is full of gas
It keeps a constant superheat in the evaporator
It would cause the low-side pressure to decrease
A low refrigerant charge

20. 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
Dirty condenser - bent condenser fins - and air recirculating over the condenser
A restricted metering device
Dirty condenser - bent condenser fins - and air recirculating over the condenser

21. 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
Both technicians are incorrect
An increase in suction pressure and an increase in discharge pressure
Bad compressor valve
Technician B

22. Why is it unsafe to operate an air conditioning system with a low charge...
The discharge pressure increases and the amperage increases
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Dirty condenser - bent condenser fins - and air recirculating over the condenser
High superheat and low discharge pressure

23. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Current in the compressor circuit
An overcharged system
Condenser fans operating during a low ambient condition and a low suction pressure
Dirty condenser - bent condenser fins - and air recirculating over the condenser

24. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Low discharge pressure - high suction pressure - and low amp draw
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Technician A is correct
Flooding the condenser - cycling condenser fans - and dampering condenser air

25. Which of the following is a common cause of an excessively low superheat on a TXV system...
A sensing bulb improperly connected to the suction line
'G' to 'C'
Low superheat
High suction pressure and low superheat

26. What are two common symptoms of refrigerant leaks in an air conditioning system...
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A sensing bulb improperly connected to the suction line
Partially frosted evaporator and high superheat
It keeps a constant superheat in the evaporator

27. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
A start capacitor and a solid-state relay
A defective circuit breaker

28. 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
A restricted metering device
Technician A
The superheat will increase and the low-side pressure will decrease

29. A hard-start kit for an air conditioning system...
Both technicians are correct
It is used to control refrigerant pressure in the compressor crankcase
Rise more than normal
Increases starting torque

30. 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 start relay
High superheat and low discharge pressure
High suction pressure and low superheat
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

31. What is the common cause of a compressor burnout...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Both technicians are incorrect
Current in the compressor circuit
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

32. What are two common symptoms of refrigerant leaks in an air conditioning system...
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Short cycling and insufficient dehumidification
Partially frosted evaporator and high superheat
An acid-core suction line drier

33. 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
Rise more than normal
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
A plugged filter drier

34. What is the purpose of a CPR valve...
The system has been overcharged+The system has air trapped in the condenser
A restricted metering device
It is used to control refrigerant pressure in the compressor crankcase
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged

35. A system that is operating with a clear sight glass shows...
'G' to 'C'
The sight glass is full of liquid+the sight glass is full of gas
A plugged filter drier
An open internal overload protector

36. When an air conditioning system has an undercharge - what happens to the superheat and the subcooling of the system...
It keeps a constant superheat in the evaporator
The superheat increases and the subcooling decreases
Technician A is correct
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

37. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
An open internal overload protector
Contains a solenoid coil and one or more sets of contacts
An increase in suction pressure and an increase in discharge pressure
An undercharge and low ambient conditions

38. What type of problems can be caused by an oversized air conditioning system...
Both technicians are incorrect
Partially frosted evaporator and high superheat
A vacuum test+oil traces around fittings+soap bubble solution
Short cycling and insufficient dehumidification

39. What is the common cause of a compressor burnout...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
The superheat will increase and the low-side pressure will decrease
Both technicians are incorrect

40. A customer calls with an insufficient cooling complaint on a 90
An increase in low-side pressure
It would cause the low-side pressure to decrease
Technician B
Flooding the condenser - cycling condenser fans - and dampering condenser air

41. A liquid-charged TXV bulb will...
Rise more than normal
Always have some liquid present in the bulb and diaphragm
Increases starting torque
50-65

42. 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
A missing air filter+improper rotation of the indoor blower+blower too small
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Technician B
Dirty condenser - bent condenser fins - and air recirculating over the condenser

43. 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
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Condenser fans operating during a low ambient condition and a low suction pressure
An increase in low-side pressure
Technician B

44. 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
Lack of airflow
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Low discharge pressure - high suction pressure - and low amp draw

45. What problem or problems can cause low discharge and suction pressure...
An undercharged system+insufficient airflow over the evaporator coil
An increase of air leakage from ductwork
3 psig
Rise more than normal

46. What are the operating pressures of an oil pressure safety switch...
A low refrigerant charge
It is used to control refrigerant pressure in the compressor crankcase
The oil pump pressure and the crankcase pressure
Technician B

47. Which of the following is a possible cause for a compressor to overheat...
A low refrigerant charge
20 to 30
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication

48. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
The superheat will increase and the low-side pressure will decrease
High suction pressure and low superheat
An overcharged system
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

49. 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
An uninsulated suction line and a restricted metering device
Technician A
Broken rings+broken valves+seized bearings
The system has been overcharged+The system has air trapped in the condenser

50. A compressor having tight bearings would cause the current value to...
Increases starting torque
Rise more than normal
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
The superheat increases and the subcooling decreases