Heat-pump components and their jobs

Core idea

Component questions become easier when each part is linked to energy flow. The evaporator absorbs heat from outdoor air into the refrigerant. The compressor raises vapour pressure and temperature. The condenser transfers heat into heating water, and the expansion device reduces refrigerant pressure before the evaporator. A reversing valve changes the refrigerant path where reverse-cycle operation is provided.

What to recognise

• The outdoor fan moves source air across the evaporator; restricted airflow reduces heat transfer.
• A plate heat exchanger or internal condenser separates refrigerant and heating-water circuits while transferring heat.
• A buffer vessel adds water volume or hydraulic separation only when the design calls for it.
• A heat-pump cylinder normally needs a coil selected for the available flow temperature and required transfer rate.
• Sensors, pumps and controls coordinate demand, flow, defrost and any backup heat.

Apply it

Diagnose by asking which circuit is affected. Poor airflow points first to source-side conditions; low heating-water flow points to pumps, strainers, air, valves or balancing; a sensor error can make sound hardware behave incorrectly. Name the measured symptom before replacing a component.

Keep the boundary clear

A buffer vessel is not automatically required, and it does not correct undersized emitters or bad control logic. Refrigerant components must be handled only by people with the appropriate competence for the refrigerant and task. Always use the appliance hydraulic schematic and manufacturer limits.