NATE Air Conditioning 1 — Questions and Answers
Question 1: What refrigerant is most commonly used in modern residential air conditioning systems in the US?
- R-22
- R-410A (Correct answer)
- R-134a
- R-404A
Correct answer: R-410A
R-410A replaced R-22 as the standard residential AC refrigerant due to R-22's ozone-depleting properties.
Question 2: What is the purpose of the metering device in a refrigeration circuit?
- Compress the refrigerant
- Remove heat from the condenser
- Reduce refrigerant pressure and control flow into the evaporator (Correct answer)
- Filter moisture from the refrigerant
Correct answer: Reduce refrigerant pressure and control flow into the evaporator
The metering device reduces high-pressure liquid refrigerant to low-pressure liquid/vapor, controlling flow into the evaporator.
Question 3: Which component in an air conditioning system is responsible for rejecting heat to the outdoors?
- Evaporator
- Compressor
- Condenser (Correct answer)
- Expansion valve
Correct answer: Condenser
The condenser releases heat absorbed from the indoor air to the outdoor environment.
Question 4: What does superheat measure in a refrigeration system?
- Temperature of liquid refrigerant leaving the condenser
- Temperature rise of vapor above the saturation point at a given pressure (Correct answer)
- Subcooling at the condenser outlet
- Compressor discharge temperature
Correct answer: Temperature rise of vapor above the saturation point at a given pressure
Superheat is the number of degrees the refrigerant vapor temperature exceeds the saturation temperature at that pressure.
Question 5: What is the typical target evaporator superheat range for a fixed-orifice metering device system?
- 0–5°F
- 5–10°F
- 10–18°F (Correct answer)
- 25–40°F
Correct answer: 10–18°F
A fixed-orifice system typically targets 10–18°F of superheat at the evaporator outlet for proper refrigerant feed.
Question 6: Which tool is used to measure the wet-bulb temperature when evaluating air conditioning performance?
- Clamp meter
- Sling psychrometer (Correct answer)
- Manifold gauge set
- Anemometer
Correct answer: Sling psychrometer
A sling psychrometer uses a wet-bulb and dry-bulb thermometer to measure relative humidity and wet-bulb temperature.
NATE Air Conditioning 1
What refrigerant is most commonly used in modern residential air conditioning systems in the US?