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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. Which of the following can cause excessive subcooling...
High superheat and low discharge pressure
The discharge pressure increases and the amperage increases
An overcharged system
3 psig

2. What are two common symptoms of an overcharged air conditioning system that uses a capillary-tube-type metering device...
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
An increase in suction pressure and an increase in discharge pressure
50-65

3. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
An increase of air leakage from ductwork
High superheat and low discharge pressure
A plugged filter drier
Evaporator and compressor

4. 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
The superheat increases and the subcooling decreases
Dirty condenser - bent condenser fins - and air recirculating over the condenser

5. What are the symptoms of a TXV air conditioning system if it has lost its charge...
The superheat will increase and the low-side pressure will decrease
Technician A is correct
Evaporator and compressor
A restricted metering device

6. What is the common cause of a compressor burnout...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
The superheat will increase and the low-side pressure will decrease
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
The sight glass is full of liquid+the sight glass is full of gas

7. 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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8. What is the purpose of the TXV...
A sensing bulb improperly connected to the suction line
It keeps a constant superheat in the evaporator
An overcharged system
An uninsulated TXV sensing bulb

9. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
Technician A is correct
An undercharged system+insufficient airflow over the evaporator coil
It would cause the low-side pressure to decrease
Bad compressor valve

10. 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
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
('Y' and 'C') and ('G' and 'C')
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
Technician B

11. What are the symptoms of an air conditioning system that has a low charge...
Increases starting torque
The low-side pressure will decrease and the evaporator coil will be partially frosted
An open internal overload protector
Technician A is correct

12. What is a common discharge temperature of an air-cooled air conditioning system that is used on a 90
The sensing bulb at a lower temperature than the valve body
110-120
Low voltage and a faulty start relay
Technician B

13. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
A restricted metering device
Evaporator and compressor
Current in the compressor circuit
20 to 30

14. A commercial customer calls on a 90
Rise more than normal
Run with high head and high suction pressure
The system has been overcharged+The system has air trapped in the condenser
The sight glass is full of liquid+the sight glass is full of gas

15. What three things can prevent an air conditioning system from releasing heat at the proper rate...
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Both technicians are correct
Technician B

16. When using a vapor-charged TXV bulb - it is necessary to have...
50-65
A sensing bulb improperly connected to the suction line
Low discharge pressure - high suction pressure - and low amp draw
The sensing bulb at a lower temperature than the valve body

17. The technician observes a pressure drop of 25 degrees across an air conditioning evaporator coil at start-up. This drop would indicate...
The sensing bulb at a lower temperature than the valve body
Lack of airflow
A start capacitor and a solid-state relay
It keeps a constant superheat in the evaporator

18. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
Both technicians are incorrect
An undercharge and low ambient conditions
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The internal overload is opened

19. Which of the following will cause excessive discharge pressures on an air conditioning system...
20 to 30
Run with high head and high suction pressure
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Technician B

20. A hard-start kit for an air conditioning system...
Whenever necessary
50-65
('Y' and 'C') and ('G' and 'C')
Increases starting torque

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...
An uninsulated suction line and a restricted metering device
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
Low voltage and a faulty start relay
An acid-core suction line drier

22. 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
The external equalizer could be plugged
Always have some liquid present in the bulb and diaphragm
Technician A is correct
Technician B

23. Which of the following will cause excessive discharge pressures on an air conditioning system...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
Technician B
A start capacitor and a solid-state relay
The low-side pressure will decrease and the evaporator coil will be partially frosted

24. 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 superheat increases and the subcooling decreases
Technician B
Low voltage and a faulty start relay
Dirty condenser - bent condenser fins - and air recirculating over the condenser

25. What causes the automatic expansion valve to close...
Broken rings+broken valves+seized bearings
The low-side pressure will decrease and the evaporator coil will be partially frosted
Evaporator and compressor
An increase in low-side pressure

26. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Lack of airflow
Bad compressor valve
Technician B
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system

27. 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
A bad thermostat
Technician A
The superheat will increase and the low-side pressure will decrease
Low superheat

28. 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 in suction pressure and an increase in discharge pressure
A defective circuit breaker
110-120

29. What causes the automatic expansion valve to close...
An uninsulated TXV sensing bulb
The superheat will increase and the low-side pressure will decrease
The superheat increases and the subcooling decreases
An increase in low-side pressure

30. The best description of a relay would be...
Lack of airflow
The superheat increases and the subcooling decreases
Contains a solenoid coil and one or more sets of contacts
A start relay

31. What are the symptoms of an air conditioning system that has a low charge...
A bad thermostat
An undercharge and low ambient conditions
The low-side pressure will decrease and the evaporator coil will be partially frosted
It is used to control refrigerant pressure in the compressor crankcase

32. What are the operating pressures of an oil pressure safety switch...
Both technicians are correct
The oil pump pressure and the crankcase pressure
Low superheat
A defective circuit breaker

33. An air conditioning unit has a suction line that is frosted up to the compressor. What faults could cause this to occur...
Contains a solenoid coil and one or more sets of contacts
Technician A is correct
Technician B
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay

34. 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
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Technician B
Rise more than normal

35. What are two common symptoms of refrigerant leaks in an air conditioning system...
An acid-core suction line drier
Partially frosted evaporator and high superheat
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Both technicians are incorrect

36. 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
The external equalizer could be plugged
3 psig
50-65

37. 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 system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
A dirty condenser - recirculation of condenser air - and a defective condenser fan
The internal overload is opened
3 psig

38. What are the symptoms of a TXV air conditioning system if it has lost its charge...
Low discharge pressure - high suction pressure - and low amp draw
Dirty condenser - bent condenser fins - and air recirculating over the condenser
The superheat will increase and the low-side pressure will decrease
Technician B

39. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
3 psig
High superheat and low discharge pressure
Short cycling and insufficient dehumidification
An uninsulated TXV sensing bulb

40. 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
A start capacitor and a solid-state relay
Run with high head and high suction pressure
An increase of air leakage from ductwork

41. What problem or problems can cause low discharge and suction pressure...
The sight glass is full of liquid+the sight glass is full of gas
An undercharged system+insufficient airflow over the evaporator coil
'G' to 'C'
Evaporator and compressor

42. Which of the following can cause low superheat in a TXV system...
A vacuum test+oil traces around fittings+soap bubble solution
An uninsulated TXV sensing bulb
The superheat will increase and the low-side pressure will decrease
Rise more than normal

43. A system that is operating with a clear sight glass shows...
Technician A
A vacuum test+oil traces around fittings+soap bubble solution
A bad thermostat
The sight glass is full of liquid+the sight glass is full of gas

44. What are possible problems that can cause the discharge-line temperature on an air conditioning system to be cool to the touch...
110-120
'G' to 'C'
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Technician A is correct

45. What are two problems that can cause an air conditioning system to have an excessively high superheat...
An uninsulated suction line and a restricted metering device
The low-side pressure will decrease and the evaporator coil will be partially frosted
110-120
Low voltage and a faulty start relay

46. Superheat is found in an air conditioning system in the...
Technician B
Evaporator and compressor
Increases starting torque
The superheat will increase and the low-side pressure will decrease

47. A commercial customer calls on a 90
It would cause the low-side pressure to decrease
Run with high head and high suction pressure
A missing air filter+improper rotation of the indoor blower+blower too small
The system has been overcharged+The system has air trapped in the condenser

48. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
('Y' and 'C') and ('G' and 'C')
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Technician B
Run with high head and high suction pressure

49. When using a vapor-charged TXV bulb - it is necessary to have...
3 psig
The sensing bulb at a lower temperature than the valve body
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

50. 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
Bad compressor valve
Broken rings+broken valves+seized bearings
Increases starting torque
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser