EPA Section 608 Universal Certification ExamCoreEasy
A technician is servicing a residential split system with R-410A. Which of the following components is primarily responsible for converting high-pressure liquid refrigerant into a low-pressure liquid-vapor mixture before it enters the evaporator?
- ACondenser
- BExpansion Device
- CCompressor
- DEvaporator
Show answer & explanationAnswer & explanation
Correct answer: B. Expansion Device
The expansion device (e.g., TXV or capillary tube) is located between the condenser and the evaporator. Its primary function is to meter the flow of high-pressure liquid refrigerant, reducing its pressure and temperature as it enters the evaporator, creating a low-pressure liquid-vapor mixture.
Why the other options are wrong
- A. The condenser rejects heat and changes high-pressure vapor into high-pressure liquid.
- C. The compressor increases the pressure and temperature of the refrigerant vapor.
- D. The evaporator absorbs heat and converts low-pressure liquid-vapor into low-pressure vapor.
Expansion Device Function
The expansion device (metering device) in a refrigeration system controls the flow of liquid refrigerant into the evaporator, reducing its pressure and temperature.
- Located between the condenser and evaporator.
- Reduces the pressure of the liquid refrigerant.
- Causes a drop in refrigerant temperature.
- Creates a mixture of liquid and vapor (flash gas) entering the evaporator.
Memory trick: Expansion device: like a gate, it drops the pressure and sets the evaporator's fate.