350 QUESTIONS AND ANSWERS
1. Q: What does BTU stand for? ANSWER British Thermal Unit - the
amount of heat required to raise the temperature of one pound of water by one
degree Fahrenheit.
2. Q: What is the purpose of a heat exchanger in an HVAC system?
ANSWER To transfer heat from one medium to another without allowing the
two mediums to mix directly.
3. Q: What is the difference between sensible heat and latent heat?
ANSWER Sensible heat causes a temperature change, while latent heat causes
a phase change without temperature change.
4. Q: What is the ideal indoor relative humidity range for comfort?
ANSWER 30% to 50% relative humidity.
5. Q: What is superheat in refrigeration systems? ANSWER The
temperature of refrigerant vapor above its saturation temperature at a given
pressure.
6. Q: What is subcooling in refrigeration systems? ANSWER The
temperature of liquid refrigerant below its saturation temperature at a given
pressure.
7. Q: What are the four main components of a basic refrigeration cycle?
ANSWER Compressor, condenser, expansion device (metering device), and
evaporator.
8. Q: What is the purpose of the evaporator in an AC system? ANSWER
To absorb heat from the indoor air and evaporate the liquid refrigerant.
9. Q: What is the function of the condenser in an AC system? ANSWER
To reject heat to the outside air and condense the refrigerant vapor back to
liquid.
,10. Q: What is ton of refrigeration? ANSWER The amount of cooling
required to freeze one ton of water in 24 hours, equal to 12,000 BTU/hr.
11. Q: What is the difference between dry bulb and wet bulb temperature?
ANSWER Dry bulb is actual air temperature; wet bulb is temperature measured
with a wet thermometer, indicating humidity effects.
12. Q: What is the purpose of a filter drier in a refrigeration system?
ANSWER To remove moisture and contaminants from the refrigerant.
13. Q: What is the difference between R-22 and R-410A refrigerants?
ANSWER R-22 is an HCFC being phased out; R-410A is an HFC replacement
with higher operating pressures.
14. Q: What is static pressure in ductwork? ANSWER The pressure exerted
equally in all directions within the duct system.
15. Q: What is the purpose of a damper in ductwork? ANSWER To control
or regulate airflow through ducts.
16. Q: What is the difference between supply and return air? ANSWER
Supply air is conditioned air delivered to spaces; return air is air drawn back to
the unit for reconditioning.
17. Q: What is MERV rating for filters? ANSWER Minimum Efficiency
Reporting Value - measures filter effectiveness from 1-20, higher numbers =
better filtration.
18. Q: What is the purpose of a thermostat? ANSWER To sense
temperature and control HVAC system operation to maintain desired
temperature.
19. Q: What is the difference between single-stage and two-stage cooling?
ANSWER Single-stage has one capacity level; two-stage has low and high
capacity for better comfort and efficiency.
20. Q: What is SEER rating? ANSWER Seasonal Energy Efficiency Ratio -
measures cooling efficiency over an entire season.
21. Q: What is the purpose of refrigerant oil in a compressor? ANSWER
To lubricate moving parts and create seals within the compressor.
22. Q: What is the difference between centrifugal and reciprocating
compressors? ANSWER Centrifugal uses rotating impeller; reciprocating
uses pistons and cylinders.
, 23. Q: What is a heat pump? ANSWER A system that can provide both
heating and cooling by reversing the refrigeration cycle.
24. Q: What is the coefficient of performance (COP)? ANSWER The ratio
of useful heating or cooling provided to energy consumed.
25. Q: What is the purpose of a sight glass in a refrigeration system?
ANSWER To visually check refrigerant condition and charge level.
26. Q: What is the difference between air-cooled and water-cooled
condensers? ANSWER Air-cooled uses outdoor air; water-cooled uses water
to reject heat.
27. Q: What is a psychrometric chart used for? ANSWER To analyze air
properties including temperature, humidity, and enthalpy relationships.
28. Q: What is the purpose of a crankcase heater? ANSWER To prevent
liquid refrigerant from migrating to the compressor during off cycles.
29. Q: What is the difference between natural and forced convection?
ANSWER Natural uses density differences; forced uses fans or pumps to move
air/fluid.
30. Q: What is enthalpy in HVAC applications? ANSWER The total heat
content of air, including both sensible and latent heat.
31. Q: What is the purpose of a service valve? ANSWER To allow
connection of service equipment for system maintenance and repair.
32. Q: What is the difference between parallel and series airflow?
ANSWER Parallel splits airflow; series moves air through components in
sequence.
33. Q: What is a TXV (Thermostatic Expansion Valve)? ANSWER A
metering device that maintains constant superheat by varying refrigerant flow.
34. Q: What is the purpose of a receiver tank? ANSWER To store liquid
refrigerant and accommodate system charge variations.
35. Q: What is the difference between positive and negative pressure?
ANSWER Positive pressure is above atmospheric; negative is below
atmospheric pressure.
36. Q: What is a heat recovery ventilator (HRV)? ANSWER A device that
exchanges heat between exhaust and supply air streams.
1. Q: What does BTU stand for? ANSWER British Thermal Unit - the
amount of heat required to raise the temperature of one pound of water by one
degree Fahrenheit.
2. Q: What is the purpose of a heat exchanger in an HVAC system?
ANSWER To transfer heat from one medium to another without allowing the
two mediums to mix directly.
3. Q: What is the difference between sensible heat and latent heat?
ANSWER Sensible heat causes a temperature change, while latent heat causes
a phase change without temperature change.
4. Q: What is the ideal indoor relative humidity range for comfort?
ANSWER 30% to 50% relative humidity.
5. Q: What is superheat in refrigeration systems? ANSWER The
temperature of refrigerant vapor above its saturation temperature at a given
pressure.
6. Q: What is subcooling in refrigeration systems? ANSWER The
temperature of liquid refrigerant below its saturation temperature at a given
pressure.
7. Q: What are the four main components of a basic refrigeration cycle?
ANSWER Compressor, condenser, expansion device (metering device), and
evaporator.
8. Q: What is the purpose of the evaporator in an AC system? ANSWER
To absorb heat from the indoor air and evaporate the liquid refrigerant.
9. Q: What is the function of the condenser in an AC system? ANSWER
To reject heat to the outside air and condense the refrigerant vapor back to
liquid.
,10. Q: What is ton of refrigeration? ANSWER The amount of cooling
required to freeze one ton of water in 24 hours, equal to 12,000 BTU/hr.
11. Q: What is the difference between dry bulb and wet bulb temperature?
ANSWER Dry bulb is actual air temperature; wet bulb is temperature measured
with a wet thermometer, indicating humidity effects.
12. Q: What is the purpose of a filter drier in a refrigeration system?
ANSWER To remove moisture and contaminants from the refrigerant.
13. Q: What is the difference between R-22 and R-410A refrigerants?
ANSWER R-22 is an HCFC being phased out; R-410A is an HFC replacement
with higher operating pressures.
14. Q: What is static pressure in ductwork? ANSWER The pressure exerted
equally in all directions within the duct system.
15. Q: What is the purpose of a damper in ductwork? ANSWER To control
or regulate airflow through ducts.
16. Q: What is the difference between supply and return air? ANSWER
Supply air is conditioned air delivered to spaces; return air is air drawn back to
the unit for reconditioning.
17. Q: What is MERV rating for filters? ANSWER Minimum Efficiency
Reporting Value - measures filter effectiveness from 1-20, higher numbers =
better filtration.
18. Q: What is the purpose of a thermostat? ANSWER To sense
temperature and control HVAC system operation to maintain desired
temperature.
19. Q: What is the difference between single-stage and two-stage cooling?
ANSWER Single-stage has one capacity level; two-stage has low and high
capacity for better comfort and efficiency.
20. Q: What is SEER rating? ANSWER Seasonal Energy Efficiency Ratio -
measures cooling efficiency over an entire season.
21. Q: What is the purpose of refrigerant oil in a compressor? ANSWER
To lubricate moving parts and create seals within the compressor.
22. Q: What is the difference between centrifugal and reciprocating
compressors? ANSWER Centrifugal uses rotating impeller; reciprocating
uses pistons and cylinders.
, 23. Q: What is a heat pump? ANSWER A system that can provide both
heating and cooling by reversing the refrigeration cycle.
24. Q: What is the coefficient of performance (COP)? ANSWER The ratio
of useful heating or cooling provided to energy consumed.
25. Q: What is the purpose of a sight glass in a refrigeration system?
ANSWER To visually check refrigerant condition and charge level.
26. Q: What is the difference between air-cooled and water-cooled
condensers? ANSWER Air-cooled uses outdoor air; water-cooled uses water
to reject heat.
27. Q: What is a psychrometric chart used for? ANSWER To analyze air
properties including temperature, humidity, and enthalpy relationships.
28. Q: What is the purpose of a crankcase heater? ANSWER To prevent
liquid refrigerant from migrating to the compressor during off cycles.
29. Q: What is the difference between natural and forced convection?
ANSWER Natural uses density differences; forced uses fans or pumps to move
air/fluid.
30. Q: What is enthalpy in HVAC applications? ANSWER The total heat
content of air, including both sensible and latent heat.
31. Q: What is the purpose of a service valve? ANSWER To allow
connection of service equipment for system maintenance and repair.
32. Q: What is the difference between parallel and series airflow?
ANSWER Parallel splits airflow; series moves air through components in
sequence.
33. Q: What is a TXV (Thermostatic Expansion Valve)? ANSWER A
metering device that maintains constant superheat by varying refrigerant flow.
34. Q: What is the purpose of a receiver tank? ANSWER To store liquid
refrigerant and accommodate system charge variations.
35. Q: What is the difference between positive and negative pressure?
ANSWER Positive pressure is above atmospheric; negative is below
atmospheric pressure.
36. Q: What is a heat recovery ventilator (HRV)? ANSWER A device that
exchanges heat between exhaust and supply air streams.
