CSLB C-20 HVAC ContractorCooling and RefrigerationEasy
What is the primary function of the evaporator coil in a residential split-system air conditioner?
- AReject heat from the refrigerant to the outdoor air
- BReduce refrigerant pressure through a fixed orifice before the condenser
- CCompress refrigerant vapor to raise its pressure and temperature
- DAbsorb heat from indoor air by boiling low-pressure refrigerant
Show answer & explanationAnswer & explanation
Correct answer: D. Absorb heat from indoor air by boiling low-pressure refrigerant
The evaporator coil is where liquid refrigerant boils off at low pressure/temperature, absorbing heat from the return air passing over the coil and cooling the space. Heat rejection happens at the condenser, compression at the compressor, and pressure reduction at the metering device—not the evaporator itself.
Why the other options are wrong
- A. This describes the condenser's job, not the evaporator's.
- B. This describes the metering device, which is located before the evaporator, not the evaporator itself.
- C. This describes the compressor's function.
Evaporator Function
The evaporator coil absorbs heat from indoor air by boiling low-pressure liquid refrigerant into vapor.
- Located on the indoor (or low-pressure) side of the system
- Refrigerant enters as a low-pressure liquid/vapor mix and leaves as superheated vapor
- Heat absorption here is the actual 'cooling' effect felt indoors
Memory trick: Evaporator = Absorbs heat, like a sponge soaking up warmth