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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 is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
A blown fuse
Rise more than normal
20 to 30
The low-side pressure will decrease and the evaporator coil will be partially frosted

2. 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
Technician B
The oil pump pressure and the crankcase pressure
The discharge pressure increases and the amperage increases

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
A vacuum test+oil traces around fittings+soap bubble solution
Both technicians are incorrect
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Short cycling and insufficient dehumidification

4. The internal overload of an air conditioning compressor senses winding temperature and...
The low-side pressure will decrease and the evaporator coil will be partially frosted
Technician B
Current in the compressor circuit
Low voltage and a faulty start relay

5. 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...
An undercharge and low ambient conditions
High superheat and low discharge pressure
It would cause the low-side pressure to decrease
3 psig

6. A liquid-charged TXV bulb will...
'G' to 'C'
20 to 30
Always have some liquid present in the bulb and diaphragm
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system

7. Which of the following is a common cause of an excessively low superheat on a TXV system...
Technician A is correct
50-65
A sensing bulb improperly connected to the suction line
Technician B

8. Insufficient airflow can be caused by...
Partially frosted evaporator and high superheat
The superheat increases and the subcooling decreases
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
An increase of air leakage from ductwork

9. 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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10. If a TXV sensing bulb had lost its charge - what effect would this have on the air conditioning system...
It would cause the low-side pressure to decrease
Technician B
Flooding the condenser - cycling condenser fans - and dampering condenser air
Low superheat

11. Which of the following could be the cause for a system's discharge and suction pressure being low...
Partially frosted evaporator and high superheat
An increase of air leakage from ductwork
A blown fuse
A restricted metering device

12. What is the common cause of a compressor burnout...
Technician A
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
An overcharged system

13. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
A start relay
50-65
An undercharge and low ambient conditions
High superheat and low discharge pressure

14. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
The discharge pressure increases and the amperage increases
An increase in suction pressure and an increase in discharge pressure
Evaporator and compressor
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

15. 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...
Run with high head and high suction pressure
It is used to control refrigerant pressure in the compressor crankcase
Low voltage and a faulty start relay
It is used to control refrigerant pressure in the compressor crankcase

16. Superheat is found in an air conditioning system in the...
Low voltage and a faulty start relay
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
Evaporator and compressor

17. Air filters should be replaced...
The oil pump pressure and the crankcase pressure
Technician B
Low discharge pressure - high suction pressure - and low amp draw
Whenever necessary

18. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
An overcharged system
Run with high head and high suction pressure
3 psig
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

19. What is the purpose of a CPR valve...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
It is used to control refrigerant pressure in the compressor crankcase
High suction pressure and low superheat
50-65

20. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
An undercharge and low ambient conditions
The system has been overcharged+The system has air trapped in the condenser
An overcharged system

21. When using a vapor-charged TXV bulb - it is necessary to have...
The external equalizer could be plugged
'G' to 'C'
An overcharged system
The sensing bulb at a lower temperature than the valve body

22. 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
An increase in suction pressure and an increase in discharge pressure
A blown fuse
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
An open internal overload protector

23. A customer who owns a split air conditioning system complains that his system has been running but his house doesn't seem to be cooling properly. When the service technician arrives on the job - he or she finds that the indoor blower is operating and
The superheat increases and the subcooling decreases
Clean the condenser coil
The internal overload is opened
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser

24. 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
The superheat increases and the subcooling decreases
Increases starting torque
A vacuum test+oil traces around fittings+soap bubble solution

25. A customer calls with an insufficient cooling complaint on a 90
A restricted metering device
A low refrigerant charge
Broken rings+broken valves+seized bearings
Technician B

26. A commercial customer calls on a 90
An undercharged system+insufficient airflow over the evaporator coil
It keeps a constant superheat in the evaporator
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
The system has been overcharged+The system has air trapped in the condenser

27. 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...
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
An overcharged system
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A blown fuse

28. What are the symptoms of an air conditioning system that has a low charge...
A restricted metering device
It is used to control refrigerant pressure in the compressor crankcase
The low-side pressure will decrease and the evaporator coil will be partially frosted
An undercharged system+insufficient airflow over the evaporator coil

29. What are the symptoms of a TXV air conditioning system if it has lost its charge...
High superheat and low discharge pressure
Clean the condenser coil
The superheat will increase and the low-side pressure will decrease
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor

30. 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
A restricted metering device
An uninsulated TXV sensing bulb
20 to 30
Technician A

31. What causes the automatic expansion valve to close...
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Technician A
An increase in low-side pressure
Run with high head and high suction pressure

32. 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
Short cycling and insufficient dehumidification
Broken rings+broken valves+seized bearings
High suction pressure and low superheat

33. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
Broken rings+broken valves+seized bearings
Bad compressor valve
The internal overload is opened
An increase in suction pressure and an increase in discharge pressure

34. The temperature range of the suction line from an air conditioning system should be...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Always have some liquid present in the bulb and diaphragm
50-65
An overcharged system

35. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Dirty condenser - bent condenser fins - and air recirculating over the condenser
High suction pressure and low superheat
Technician B
Short cycling and insufficient dehumidification

36. What causes the automatic expansion valve to close...
Both technicians are correct
An increase in low-side pressure
Low voltage and a faulty start relay
Dirty condenser - bent condenser fins - and air recirculating over the condenser

37. A system that uses a thermal electric expansion valve...
Whenever necessary
Flooding the condenser - cycling condenser fans - and dampering condenser air
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Contains a solenoid coil and one or more sets of contacts

38. 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
20 to 30
An increase in low-side pressure
It keeps a constant superheat in the evaporator

39. 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
Short cycling and insufficient dehumidification
Rise more than normal
Technician B

40. What is the purpose of a CPR valve...
The external equalizer could be plugged
It is used to control refrigerant pressure in the compressor crankcase
Increases starting torque
An uninsulated suction line and a restricted metering device

41. 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
It would cause the low-side pressure to decrease
Both technicians are incorrect
Technician A is correct
A start relay

42. 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 open internal overload protector
Technician B
A missing air filter+improper rotation of the indoor blower+blower too small

43. A commercial customer calls on a 90
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Low voltage and a faulty start relay
Condenser fans operating during a low ambient condition and a low suction pressure
The system has been overcharged+The system has air trapped in the condenser

44. What type of problems can be caused by an oversized air conditioning system...
Technician B
Short cycling and insufficient dehumidification
An increase of air leakage from ductwork
20 to 30

45. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
Whenever necessary
Contains a solenoid coil and one or more sets of contacts
Low voltage and a faulty start relay
The discharge pressure increases and the amperage increases

46. Why is it unsafe to operate an air conditioning system with a low charge...
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Current in the compressor circuit
Bad compressor valve
Current in the compressor circuit

47. The internal overload of an air conditioning compressor senses winding temperature and...
Current in the compressor circuit
The superheat increases and the subcooling decreases
Condenser air being recirculated over the condenser+air trapped in the condenser due to poor service procedures+an overcharged air conditioning system
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil

48. 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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49. What three things can prevent an air conditioning system from releasing heat at the proper rate...
Broken rings+broken valves+seized bearings
A blown fuse
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
A dirty condenser - recirculation of condenser air - and a defective condenser fan

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
An undercharge and low ambient conditions
The sight glass is full of liquid+the sight glass is full of gas
Short cycling and insufficient dehumidification