CSLB C-20 HVAC ContractorHeating SystemsMedium
In a heat pump system, what component allows the unit to switch between heating and cooling modes by redirecting refrigerant flow?
- AThermostatic expansion valve
- BBi-flow filter drier
- CSuction line accumulator
- DReversing valve
Show answer & explanationAnswer & explanation
Correct answer: D. Reversing valve
The reversing valve, controlled by a solenoid, changes the direction of refrigerant flow between the indoor and outdoor coils, allowing the same coils to function as either evaporator or condenser depending on whether the system is in heating or cooling mode.
Why the other options are wrong
- A. The expansion valve meters refrigerant flow but doesn't reverse cycle direction.
- B. A bi-flow filter drier allows filtration in either direction but does not control mode switching.
- C. An accumulator protects the compressor from liquid refrigerant, unrelated to mode switching.
Reversing Valve
A four-way solenoid valve in a heat pump that redirects refrigerant flow, allowing the system to switch between heating and cooling modes.
- Also called a four-way valve
- Energized position typically corresponds to cooling mode in most designs
- Failure can leave unit stuck in one mode
Memory trick: Flip the valve, flip the season.