1. Q: What is the basic principle of refrigeration? ANSWER Heat transfer
from a lower temperature area to a higher temperature area using mechanical
work, typically through vapor compression cycle.
2. Q: Name the four main components of a basic refrigeration system.
ANSWER Compressor, condenser, expansion device (metering device), and
evaporator.
3. Q: What happens in the evaporator? ANSWER Low-pressure liquid
refrigerant absorbs heat and changes to vapor, providing cooling effect.
4. Q: What is the function of the compressor in a refrigeration system?
ANSWER To compress low-pressure refrigerant vapor into high-pressure, high-
temperature vapor and circulate refrigerant through the system.
5. Q: What occurs in the condenser? ANSWER High-pressure refrigerant
vapor releases heat to the surrounding medium and condenses into liquid.
6. Q: What is the purpose of the expansion valve? ANSWER To reduce
pressure and temperature of liquid refrigerant before it enters the evaporator.
7. Q: What is superheat? ANSWER The amount of heat added to vapor
above its saturation temperature at a given pressure.
8. Q: What is subcooling? ANSWER The amount of heat removed from
liquid refrigerant below its saturation temperature at a given pressure.
9. Q: What is the saturation temperature? ANSWER The temperature at
which a refrigerant changes phase (liquid to vapor or vapor to liquid) at a given
pressure.
10. Q: What does COP stand for in refrigeration? ANSWER Coefficient of
Performance - the ratio of useful cooling effect to work input.
,11. Q: What is the difference between sensible heat and latent heat?
ANSWER Sensible heat causes temperature change without phase change;
latent heat causes phase change without temperature change.
12. Q: What is a ton of refrigeration? ANSWER The amount of cooling
required to freeze one ton (2000 lbs) of water at 32°F in 24 hours, equal to
12,000 BTU/hr.
13. Q: What is the purpose of a receiver tank? ANSWER To store liquid
refrigerant and ensure adequate refrigerant supply to the expansion valve.
14. Q: What is flash gas? ANSWER Refrigerant that vaporizes instantly when
pressure drops across the expansion device.
15. Q: What happens if there is insufficient superheat? ANSWER Liquid
refrigerant may return to the compressor, potentially causing damage (liquid
slugging).
16. Q: What is the critical temperature of a refrigerant? ANSWER The
temperature above which the refrigerant cannot be condensed regardless of
pressure applied.
17. Q: What is meant by refrigerant flooding? ANSWER Liquid refrigerant
returning to the compressor instead of vapor only.
18. Q: What causes high head pressure in a refrigeration system?
ANSWER Dirty condenser, overcharge, non-condensables, insufficient airflow,
or high ambient temperature.
19. Q: What causes low suction pressure? ANSWER Undercharge, dirty
evaporator, restricted metering device, or insufficient airflow.
20. Q: What is the purpose of a sight glass? ANSWER To visually check
refrigerant flow and determine if the system has adequate refrigerant charge.
21. Q: What does it mean when bubbles appear in the sight glass?
ANSWER Usually indicates low refrigerant charge or flash gas due to
restriction.
22. Q: What is a hot gas bypass valve used for? ANSWER To maintain
minimum load on the compressor during light load conditions.
23. Q: What is the function of an accumulator? ANSWER To prevent liquid
refrigerant from entering the compressor suction line.
, 24. Q: What is a crankcase heater? ANSWER An electric heating element
that prevents refrigerant from condensing in the compressor crankcase during
off cycles.
25. Q: What is the purpose of oil in a refrigeration compressor? ANSWER
To lubricate moving parts, seal clearances, and help cool the compressor.
26. Q: What is oil logging? ANSWER When refrigerant oil fails to return to
the compressor and accumulates in other system components.
27. Q: What is the difference between hermetic and semi-hermetic
compressors? ANSWER Hermetic compressors are welded shut and not
serviceable; semi-hermetic can be opened and repaired.
28. Q: What is a scroll compressor? ANSWER A type of positive
displacement compressor using two spiral-shaped scrolls to compress
refrigerant.
29. Q: What causes compressor short cycling? ANSWER Low refrigerant
charge, high head pressure, electrical issues, or thermostat problems.
30. Q: What is the purpose of a filter drier? ANSWER To remove moisture,
acids, and contaminants from the refrigerant system.
31. Q: When should a filter drier be replaced? ANSWER When pressure
drop exceeds manufacturer specifications or after system contamination.
32. Q: What is a reversing valve? ANSWER A valve that changes refrigerant
flow direction in heat pump systems for heating and cooling modes.
33. Q: What is defrost cycle? ANSWER Process of removing ice buildup
from evaporator coils in low-temperature applications.
34. Q: What are the types of defrost methods? ANSWER Electric defrost,
hot gas defrost, water defrost, and air defrost.
35. Q: What is a solenoid valve used for? ANSWER To control refrigerant
flow electrically in response to system demands.
36. Q: What is meant by pump down? ANSWER Operating the compressor
while stopping refrigerant flow to move refrigerant from evaporator to receiver.
37. Q: What causes ice formation on evaporator coils? ANSWER Low
airflow, low refrigerant charge, dirty coils, or operating below freezing
conditions.
from a lower temperature area to a higher temperature area using mechanical
work, typically through vapor compression cycle.
2. Q: Name the four main components of a basic refrigeration system.
ANSWER Compressor, condenser, expansion device (metering device), and
evaporator.
3. Q: What happens in the evaporator? ANSWER Low-pressure liquid
refrigerant absorbs heat and changes to vapor, providing cooling effect.
4. Q: What is the function of the compressor in a refrigeration system?
ANSWER To compress low-pressure refrigerant vapor into high-pressure, high-
temperature vapor and circulate refrigerant through the system.
5. Q: What occurs in the condenser? ANSWER High-pressure refrigerant
vapor releases heat to the surrounding medium and condenses into liquid.
6. Q: What is the purpose of the expansion valve? ANSWER To reduce
pressure and temperature of liquid refrigerant before it enters the evaporator.
7. Q: What is superheat? ANSWER The amount of heat added to vapor
above its saturation temperature at a given pressure.
8. Q: What is subcooling? ANSWER The amount of heat removed from
liquid refrigerant below its saturation temperature at a given pressure.
9. Q: What is the saturation temperature? ANSWER The temperature at
which a refrigerant changes phase (liquid to vapor or vapor to liquid) at a given
pressure.
10. Q: What does COP stand for in refrigeration? ANSWER Coefficient of
Performance - the ratio of useful cooling effect to work input.
,11. Q: What is the difference between sensible heat and latent heat?
ANSWER Sensible heat causes temperature change without phase change;
latent heat causes phase change without temperature change.
12. Q: What is a ton of refrigeration? ANSWER The amount of cooling
required to freeze one ton (2000 lbs) of water at 32°F in 24 hours, equal to
12,000 BTU/hr.
13. Q: What is the purpose of a receiver tank? ANSWER To store liquid
refrigerant and ensure adequate refrigerant supply to the expansion valve.
14. Q: What is flash gas? ANSWER Refrigerant that vaporizes instantly when
pressure drops across the expansion device.
15. Q: What happens if there is insufficient superheat? ANSWER Liquid
refrigerant may return to the compressor, potentially causing damage (liquid
slugging).
16. Q: What is the critical temperature of a refrigerant? ANSWER The
temperature above which the refrigerant cannot be condensed regardless of
pressure applied.
17. Q: What is meant by refrigerant flooding? ANSWER Liquid refrigerant
returning to the compressor instead of vapor only.
18. Q: What causes high head pressure in a refrigeration system?
ANSWER Dirty condenser, overcharge, non-condensables, insufficient airflow,
or high ambient temperature.
19. Q: What causes low suction pressure? ANSWER Undercharge, dirty
evaporator, restricted metering device, or insufficient airflow.
20. Q: What is the purpose of a sight glass? ANSWER To visually check
refrigerant flow and determine if the system has adequate refrigerant charge.
21. Q: What does it mean when bubbles appear in the sight glass?
ANSWER Usually indicates low refrigerant charge or flash gas due to
restriction.
22. Q: What is a hot gas bypass valve used for? ANSWER To maintain
minimum load on the compressor during light load conditions.
23. Q: What is the function of an accumulator? ANSWER To prevent liquid
refrigerant from entering the compressor suction line.
, 24. Q: What is a crankcase heater? ANSWER An electric heating element
that prevents refrigerant from condensing in the compressor crankcase during
off cycles.
25. Q: What is the purpose of oil in a refrigeration compressor? ANSWER
To lubricate moving parts, seal clearances, and help cool the compressor.
26. Q: What is oil logging? ANSWER When refrigerant oil fails to return to
the compressor and accumulates in other system components.
27. Q: What is the difference between hermetic and semi-hermetic
compressors? ANSWER Hermetic compressors are welded shut and not
serviceable; semi-hermetic can be opened and repaired.
28. Q: What is a scroll compressor? ANSWER A type of positive
displacement compressor using two spiral-shaped scrolls to compress
refrigerant.
29. Q: What causes compressor short cycling? ANSWER Low refrigerant
charge, high head pressure, electrical issues, or thermostat problems.
30. Q: What is the purpose of a filter drier? ANSWER To remove moisture,
acids, and contaminants from the refrigerant system.
31. Q: When should a filter drier be replaced? ANSWER When pressure
drop exceeds manufacturer specifications or after system contamination.
32. Q: What is a reversing valve? ANSWER A valve that changes refrigerant
flow direction in heat pump systems for heating and cooling modes.
33. Q: What is defrost cycle? ANSWER Process of removing ice buildup
from evaporator coils in low-temperature applications.
34. Q: What are the types of defrost methods? ANSWER Electric defrost,
hot gas defrost, water defrost, and air defrost.
35. Q: What is a solenoid valve used for? ANSWER To control refrigerant
flow electrically in response to system demands.
36. Q: What is meant by pump down? ANSWER Operating the compressor
while stopping refrigerant flow to move refrigerant from evaporator to receiver.
37. Q: What causes ice formation on evaporator coils? ANSWER Low
airflow, low refrigerant charge, dirty coils, or operating below freezing
conditions.
