HVAC Refrigeration Fundamentals 1 — Questions and Answers
Question 1: What is the primary purpose of the refrigerant in an HVAC system?
- To lubricate the compressor
- To transfer heat from inside to outside (Correct answer)
- To filter the air supply
- To increase static pressure
Correct answer: To transfer heat from inside to outside
Refrigerant absorbs heat indoors at the evaporator and releases it outdoors at the condenser, transferring heat out of the conditioned space.
Question 2: In the refrigeration cycle, where does the refrigerant change from a low-pressure gas to a high-pressure gas?
- Expansion valve
- Condenser
- Evaporator
- Compressor (Correct answer)
Correct answer: Compressor
The compressor takes low-pressure refrigerant vapor and compresses it into a high-temperature, high-pressure gas.
Question 3: What is superheat in an HVAC system?
- Refrigerant temperature above its boiling point at a given pressure (Correct answer)
- Refrigerant pressure above normal operating range
- The temperature difference across the condenser coil
- Excessive heat buildup in the compressor motor
Correct answer: Refrigerant temperature above its boiling point at a given pressure
Superheat is the number of degrees the refrigerant vapor is heated above its saturation (boiling) temperature at a given pressure.
Question 4: What does subcooling refer to in a refrigeration system?
- Cooling below ambient outdoor temperature
- Liquid refrigerant cooled below its condensing temperature (Correct answer)
- Running the system below minimum design load
- Evaporator coil temperature below freezing
Correct answer: Liquid refrigerant cooled below its condensing temperature
Subcooling is the number of degrees the liquid refrigerant has been cooled below its saturation temperature at condenser pressure.
Question 5: Which component in the refrigeration cycle causes the refrigerant to drop in pressure and temperature?
- Compressor
- Condenser
- Metering device (expansion valve) (Correct answer)
- Filter-drier
Correct answer: Metering device (expansion valve)
The metering device (TXV or fixed orifice) restricts refrigerant flow, causing a pressure drop that lowers the refrigerant's temperature.
Question 6: What is the saturation temperature of a refrigerant?
- The temperature at which refrigerant absorbs all moisture
- The temperature at which refrigerant changes state at a given pressure (Correct answer)
- The maximum operating temperature of the system
- The temperature reading on the compressor discharge line
Correct answer: The temperature at which refrigerant changes state at a given pressure
Saturation temperature is the temperature at which a refrigerant changes between liquid and vapor states at a specific pressure.
HVAC Refrigeration Fundamentals 1
What is the primary purpose of the refrigerant in an HVAC system?