313D Fundamentals of Air Conditioning Systems 3 — Questions and Answers
Question 1: What is the function of a filter-drier in a refrigerant circuit?
- Measure system superheat
- Remove moisture and contaminants from the refrigerant (Correct answer)
- Regulate refrigerant flow to the evaporator
- Sense outdoor ambient temperature
Correct answer: Remove moisture and contaminants from the refrigerant
The filter-drier contains desiccant material that absorbs moisture and captures particulates to protect system components.
Question 2: Which pressure in an air conditioning system is referred to as the 'high side'?
- Pressure at the evaporator outlet
- Pressure between the compressor discharge and the metering device inlet (Correct answer)
- Pressure at the compressor suction port
- Pressure inside the indoor ductwork
Correct answer: Pressure between the compressor discharge and the metering device inlet
The high side spans from compressor discharge through the condenser and liquid line to the inlet of the metering device.
Question 3: What happens to the boiling point of a refrigerant when pressure increases?
- The boiling point decreases
- The boiling point stays the same
- The boiling point increases (Correct answer)
- The refrigerant solidifies
Correct answer: The boiling point increases
Higher pressure raises the saturation (boiling) temperature of a refrigerant, which is why condenser pressures are higher than evaporator pressures.
Question 4: A technician measures a suction pressure equivalent to 40°F saturation temperature. The suction line temperature is 50°F. What is the superheat?
- 10°F (Correct answer)
- 40°F
- 50°F
- 90°F
Correct answer: 10°F
Superheat equals the actual suction line temperature (50°F) minus the saturation temperature at suction pressure (40°F), which is 10°F.
Question 5: Which refrigerant is classified as an HFC and is commonly used in residential air conditioning systems manufactured after 2010?
- R-22
- R-410A (Correct answer)
- R-12
- R-502
Correct answer: R-410A
R-410A is an HFC refrigerant that replaced R-22 in residential AC systems due to its zero ozone depletion potential.
Question 6: What is the purpose of the reversing valve in a heat pump system?
- To regulate refrigerant flow based on outdoor temperature
- To reverse refrigerant flow direction, switching between heating and cooling modes (Correct answer)
- To prevent refrigerant from flowing back through the compressor
- To equalize high and low side pressures during shutdown
Correct answer: To reverse refrigerant flow direction, switching between heating and cooling modes
The reversing valve redirects refrigerant flow so the outdoor coil becomes the evaporator in cooling mode and the condenser in heating mode, or vice versa.
Question 7: What does SEER stand for and what does it measure?
- Seasonal Energy Efficiency Ratio — cooling output per unit of electrical energy input over a season (Correct answer)
- Standard Equipment Efficiency Rating — maximum BTU capacity
- System Electrical Efficiency Review — compressor amp draw
- Seasonal Evaporator Evaporation Rate — pounds of water removed per hour
Correct answer: Seasonal Energy Efficiency Ratio — cooling output per unit of electrical energy input over a season
SEER measures the total cooling output in BTUs divided by the total electrical energy consumed in watt-hours over a typical cooling season.
313D Fundamentals of Air Conditioning Systems 3
What is the function of a filter-drier in a refrigerant circuit?