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Test your basic knowledge |
NATE Air Conditioning Troubleshooting
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Subjects
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engineering
,
nate
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...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An overcharged system
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
Bad compressor valve
2. What are three methods for controlling a system's high-side pressure during low ambient conditions...
Broken rings+broken valves+seized bearings
Flooding the condenser - cycling condenser fans - and dampering condenser air
Bad compressor valve
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
3. 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
Clean the condenser coil
It would cause the low-side pressure to decrease
An increase in suction pressure and an increase in discharge pressure
4. 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...
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
High suction pressure and low superheat
The internal overload is opened
A dirty condenser - recirculation of condenser air - and a defective condenser fan
5. 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
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Low voltage and a faulty start relay
Technician B
('Y' and 'C') and ('G' and 'C')
6. What three things can prevent an air conditioning system from absorbing heat at the proper rate...
The sensing bulb at a lower temperature than the valve body
It would cause the low-side pressure to decrease
A dirty evaporator coil - a defective evaporator fan - and an iced-up evaporator coil
Broken rings+broken valves+seized bearings
7. 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
A restricted metering device
The internal overload is opened
Technician A is correct
The system could be undercharged+The compressor could have bad valves+The system could have a restricted metering device
8. Which of the following is a common cause of an excessively low superheat on a TXV system...
Short cycling and insufficient dehumidification
An uninsulated TXV sensing bulb
A sensing bulb improperly connected to the suction line
High suction pressure and low superheat
9. 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
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
110-120
Broken rings+broken valves+seized bearings
Both technicians are correct
10. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
Rise more than normal
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
A plugged filter drier
11. What problem can cause an increase of discharge pressure and an increase of suction pressure...
Both technicians are incorrect
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An overcharged system
3 psig
12. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
It is used to control refrigerant pressure in the compressor crankcase
Increases starting torque
High suction pressure and low superheat
A dirty condenser - recirculation of condenser air - and a defective condenser fan
13. A technician receives an air conditioning service call stating that the system is operating but isn't cooling properly. When the technician arrives - she notices that the compressor has recently been changed and it is an are-22 system. She checks the
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Broken rings+broken valves+seized bearings
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
14. What are common methods that are used for leak-testing a system...
Improper system evacuation during installation+short cycling of the system+excessively dirty condenser
Low discharge pressure - high suction pressure - and low amp draw
A vacuum test+oil traces around fittings+soap bubble solution
Technician B
15. A liquid-charged TXV bulb will...
An overcharged system
Always have some liquid present in the bulb and diaphragm
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
An increase in suction pressure and an increase in discharge pressure
16. 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
A start capacitor and a solid-state relay
Technician B
3 psig
Lack of airflow
17. 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...
Bad compressor valve
It would cause the low-side pressure to decrease
A blown fuse
A start relay
18. Why is it unsafe to operate an air conditioning system with a low charge...
Partially frosted evaporator and high superheat
The discharge pressure increases and the amperage increases
An uninsulated suction line and a restricted metering device
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
19. 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
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The internal overload is opened
('Y' and 'C') and ('G' and 'C')
Technician B
20. 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
Bad compressor valve
'G' to 'C'
Technician A is correct
21. A commercial customer calls on a 90
A blown fuse
Low superheat
The system has been overcharged+The system has air trapped in the condenser
Short cycling and insufficient dehumidification
22. When using a vapor-charged TXV bulb - it is necessary to have...
Bad compressor valve
The sensing bulb at a lower temperature than the valve body
A blown fuse
('Y' and 'C') and ('G' and 'C')
23. Superheat is found in an air conditioning system in the...
Technician A is correct
Dirty condenser - bent condenser fins - and air recirculating over the condenser
Evaporator and compressor
Run with high head and high suction pressure
24. 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
Clean the condenser coil
Run with high head and high suction pressure
The superheat will increase and the low-side pressure will decrease
Evaporator and compressor
25. On an are-22 air conditioning system - the suction-line filter drier should be changed when the pressure drop dictates...
Whenever necessary
50-65
3 psig
The superheat will increase and the low-side pressure will decrease
26. 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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27. What three things can prevent an air conditioning system from releasing heat at the proper rate...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
Flooding the condenser - cycling condenser fans - and dampering condenser air
Evaporator and compressor
It keeps a constant superheat in the evaporator
28. What problem or problems can cause the discharge pressure to be low and the suction pressure to be high...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Rise more than normal
Bad compressor valve
The sight glass is full of liquid+the sight glass is full of gas
29. What is the purpose of a CPR valve...
A restricted metering device
It would cause the low-side pressure to decrease
A low refrigerant charge
It is used to control refrigerant pressure in the compressor crankcase
30. What types of symptoms will be present if the sensing bulb of a TXV is not properly connected...
Partially frosted evaporator and high superheat
Technician A
The system has been overcharged+The system has air trapped in the condenser
High suction pressure and low superheat
31. What are two problems that can cause an air conditioning system to have an excessively high superheat...
110-120
An uninsulated suction line and a restricted metering device
('Y' and 'C') and ('G' and 'C')
A low refrigerant charge
32. 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 superheat increases and the subcooling decreases
A plugged filter drier
Short cycling and insufficient dehumidification
Technician A is correct
33. What component is most often the cause of a start capacitor failure...
A dirty condenser - recirculation of condenser air - and a defective condenser fan
A start relay
Technician B
The external equalizer could be plugged
34. What are two common problems that can cause a sight glass in an air conditioning to have bubbles...
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
An undercharge and low ambient conditions
An uninsulated suction line and a restricted metering device
A blown fuse
35. What controls are used on air conditioning or refrigeration systems that incorporate an automatic pump-down system...
An undercharge and low ambient conditions
An acid-core suction line drier
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
36. 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...
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
Condenser fans operating during a low ambient condition and a low suction pressure
A low amp draw - a decrease in high-side pressure - and a decrease in low-side pressure
Both technicians are incorrect
37. What is the purpose of an EPR valve...
Evaporator and compressor
Broken rings+broken valves+seized bearings
It increases pressure in a high-temperature evaporator coil when it is used on a dual-evaporator system
Lack of airflow
38. 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
The sight glass is full of liquid+the sight glass is full of gas
Increases starting torque
An undercharged system+insufficient airflow over the evaporator coil
An open internal overload protector
39. Name two symptoms that are common to an over-charged air conditioning system and a system that has a dirty condenser.
Low superheat
The system was improperly serviced and it has air trapped in the condenser or the unit has been overcharged
It would cause the low-side pressure to decrease
The discharge pressure increases and the amperage increases
40. 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
Technician B
Both technicians are incorrect
It can seize the compressor because of excessive heat+It can seize the compressor because of lack of lubrication
41. 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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42. Which of the following could be the cause for a system's discharge and suction pressure being low...
High suction pressure and low superheat
A restricted metering device
Technician A is correct
Current in the compressor circuit
43. What are the operating pressures of an oil pressure safety switch...
The oil pump pressure and the crankcase pressure
It is used to control refrigerant pressure in the compressor crankcase
Both technicians are incorrect
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
44. A system that uses a thermal electric expansion valve...
Both technicians are incorrect
Technician B
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
Technician A
45. What is a common temperature difference between the condensing temperature on an air-cooled condensing unit and the outdoor ambient temperature...
Can use the thermal electric expansion valve instead of a liquid-line solenoid as part of the pump-down system
20 to 30
Evaporator and compressor
An increase in suction pressure and an increase in discharge pressure
46. What problem can cause an increase of discharge pressure and an increase of suction pressure...
An overcharged system
A thermostat cycles the liquid-line solenoid - and a low-pressure switch controls the compressor
The superheat will increase and the low-side pressure will decrease
Clean the condenser coil
47. What is a possible cause of a sweat or frost pattern downstream from a sight glass and filter dryer...
An increase in suction pressure and an increase in discharge pressure
A plugged filter drier
Always have some liquid present in the bulb and diaphragm
Current in the compressor circuit
48. An air conditioning system using a fixed-orifice metering device and with noncondensables in the system will cause...
Run with high head and high suction pressure
Partially frosted evaporator and high superheat
Low discharge pressure - high suction pressure - and low amp draw
Both technicians are correct
49. A rooftop package system keeps tripping out on the high-pressure switch. What are three possible causes for this problem...
Technician B
A start capacitor and a solid-state relay
A dirty evaporator coil+a plugged air filter+a bad indoor blower relay
Dirty condenser - bent condenser fins - and air recirculating over the condenser
50. 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
A blown fuse
A vacuum test+oil traces around fittings+soap bubble solution
Technician B
Partially frosted evaporator and high superheat
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