Heat pump and air conditioning components
A practical reference accordion for the major components found across air source, ground source, water source, exhaust air, air-to-air, air-to-water, hybrid, monobloc, split, VRF/VRV and conventional air conditioning systems.
The electrically driven heart of the refrigeration circuit.
Almost all vapour-compression heat pumps and air conditioners: ASHP, GSHP, WSHP, air-to-air, air-to-water, split, monobloc, VRF/VRV and chillers.
It draws in low-pressure refrigerant vapour and compresses it into a hotter, higher-pressure vapour so heat can be rejected at the condenser.
The heat exchanger where refrigerant boils and absorbs heat.
All heat pump and air conditioning systems. In heating mode it is normally the outdoor/source-side exchanger; in cooling mode it is often the indoor coil.
Low-pressure liquid/mixed refrigerant absorbs heat from air, ground loop or water and evaporates into vapour.
The heat exchanger where refrigerant condenses and releases useful heat.
All heat pumps and air conditioners. In air-to-water heating it is often a plate heat exchanger transferring heat into heating water.
Hot high-pressure vapour gives up heat, changes back into liquid and sends that heat into air, water or a process circuit.
A controlled restriction that drops refrigerant pressure before the evaporator.
All modern heat pumps and air conditioners, usually as an electronic expansion valve; simpler systems may use TXV/TEV or capillary tubes.
It meters liquid refrigerant into the evaporator, creating a low-pressure cold mixture ready to absorb heat.
A valve that changes the direction of refrigerant flow.
Reversible air conditioners, air-to-air heat pumps, many air-to-water heat pumps and systems with active cooling or defrost.
It swaps which coil acts as the evaporator and which acts as the condenser, allowing heating, cooling or defrost operation.
A refrigerant-line component containing desiccant and filtration material.
Many split, commercial, refrigeration, chiller and serviceable heat pump systems.
It traps moisture, acids and debris to protect the expansion valve and compressor.
A small viewing window in the refrigerant line.
Common on larger commercial systems, chillers, refrigeration plant and some split systems.
It helps engineers inspect liquid condition and sometimes indicates moisture contamination through a colour-changing element.
A vessel in the suction line before the compressor.
Common in heat pumps, refrigeration systems and systems where liquid return risk exists.
It separates liquid refrigerant from vapour so the compressor mainly receives vapour, preventing liquid slugging.
A storage vessel for liquid refrigerant.
Many commercial refrigeration systems, chillers and some heat pumps, especially where charge volume varies.
It holds surplus liquid refrigerant and helps maintain a stable supply to the expansion device.
A valve or access point used for commissioning, service and diagnostics.
Split systems, monobloc factory circuits, VRF, chillers and most serviceable refrigeration circuits.
Engineers connect gauges, vacuum pumps or recovery equipment to measure pressure, evacuate, charge or recover refrigerant.
A separator that removes compressor oil from hot discharge gas.
Larger commercial heat pumps, VRF/VRV, chillers and refrigeration systems.
It captures oil carried by the refrigerant and returns it to the compressor to maintain lubrication.
A rotating air mover, usually axial in outdoor units and axial or centrifugal in indoor units.
ASHP outdoor units, air conditioners, air-to-air heat pumps, fan coils, air handlers, exhaust air heat pumps and ducted systems.
It moves air across a heat exchanger so heat can be absorbed or rejected efficiently.
A tube-and-fin heat exchanger for transferring heat between air and refrigerant or water.
Outdoor ASHP units, air conditioners, fan coils, air handlers, chillers and dry coolers.
Air passes over thin fins connected to tubes, increasing surface area for heat transfer.
A removable filter that catches airborne particles before they reach the coil or fan.
Air-to-air heat pumps, wall splits, ducted AC, fan coils, air handlers and exhaust air systems.
It traps dust and debris to protect heat exchangers, maintain airflow and improve indoor air cleanliness.
A tray and drain path that collect water forming on a cold coil.
Air conditioners, fan coils, ducted cooling systems and heat pumps operating in cooling or dehumidification.
Moisture condenses on the cold coil, drips into the tray and drains by gravity or via a condensate pump.
The outlet or inlet fitting that shapes and directs airflow.
Wall splits, cassette units, ducted air conditioning, MVHR-linked systems and fan coils.
It guides supply or return air, controlling throw, direction, mixing and comfort.
Sheet metal or flexible air passages distributing air around a building.
Ducted air-to-air heat pumps, central air conditioning, air handlers and some exhaust air systems.
Fans push supply air through ducts and pull return air back, creating a controlled air circuit.
A compact heat exchanger made from stacked plates.
Air-to-water and water-to-water heat pumps, hydroboxes, chillers, HIUs and hydraulic separation arrangements.
Two fluids pass through alternate channels, transferring heat through thin metal plates without mixing.
A small pump that moves heating water through circuits.
Air-to-water, ground source, hybrid, buffer tank, UFH, radiator and DHW primary systems.
An electric motor turns an impeller, creating pressure difference to circulate water through pipework and emitters.
A water vessel that adds volume or hydraulic separation to the heating circuit.
Many air-to-water and ground source systems, especially with low system volume, zoning or variable flow.
It stabilises flow, reduces short cycling and can separate heat pump flow from heating distribution flow.
A hydraulic component that separates primary and secondary water circuits.
Hybrid boiler/heat pump systems, larger heat pumps, cascades and complex multi-zone systems.
It allows different pumps and circuits to operate without fighting each other, while still transferring heat through mixed water flow.
A valve that opens when circuit pressure rises above a set point.
Some radiator systems, legacy systems, boiler hybrids and installations with closing valves or TRVs.
It provides a minimum flow path when emitters close, protecting pumps and maintaining circulation.
A filter that removes sludge, magnetite and debris from heating water.
Most hydronic heat pump systems and boiler/heat pump hybrids.
Water slows inside the body; magnets and separation surfaces capture particles before they damage pumps, valves or heat exchangers.
A device for removing trapped air or microbubbles from water circuits.
Hydronic heat pumps, boiler hybrids, UFH manifolds, cylinders and high points in pipework.
It separates bubbles from flowing water and vents them automatically or manually to prevent noise, corrosion and poor circulation.
A wall-mounted heat emitter containing heating water.
Air-to-water, ground source, hybrid and conventional wet heating systems.
Hot water flows through internal waterways; heat is emitted into the room by convection and radiation.
Pipework embedded in or beneath the floor to create a large low-temperature emitter.
Air-to-water, ground source and hybrid systems, especially new-build and retrofit floor zones.
Warm water circulates through floor loops and spreads heat over a large surface area, allowing lower flow temperatures.
A terminal unit with a coil and fan for heating or cooling rooms.
Air-to-water systems with cooling, chillers, commercial heat pumps and some domestic installations.
Water passes through a coil while a fan blows room air across it, transferring heat quickly.
A room unit containing a refrigerant coil, fan, filter and air outlet.
Split air conditioners and air-to-air heat pumps.
It moves room air across a refrigerant coil to heat, cool or dehumidify the space.
A ceiling-mounted indoor air unit with multi-directional airflow.
Commercial split, multi-split and VRF/VRV air conditioning and heat pump systems.
It draws room air through the centre, passes it over a coil and supplies conditioned air through outlet vanes.
A storage tank for domestic hot water.
Air-to-water, ground source, exhaust air and hybrid heat pump systems that provide DHW.
Potable water is stored in the tank and heated by a coil, external heat exchanger or direct refrigerant/water arrangement.
A coiled heat exchanger inside a hot water cylinder.
Indirect hot water cylinders, heat pump cylinders, solar thermal cylinders and twin-coil cylinders.
Primary heating water flows through the coil and transfers heat through the coil wall into stored potable water.
An electric resistance heater fitted into a cylinder.
Most heat pump hot water cylinders and many thermal stores.
Electric current heats an element directly, providing backup, boost or high-temperature pasteurisation cycles.
A valve that blends hot and cold water to a safe outlet temperature.
DHW systems, cylinders, bathrooms, healthcare settings and some heat pump cylinder packages.
A thermostatic element adjusts the hot/cold mix to maintain a target outlet temperature and reduce scald risk.
A recirculation loop that keeps hot water close to outlets.
Larger homes, commercial buildings, apartments, hotels and systems with long pipe runs.
A small pump circulates hot water around a loop so taps receive hot water faster, at the cost of extra heat loss if poorly controlled.
An electrically actuated on/off valve.
Zoned heating systems, DHW priority circuits, UFH manifolds and hybrid installations.
A motor opens or closes the valve to allow or stop water flow to a zone or cylinder coil.
A valve that directs flow between two outlets or blends two paths.
Heat pump systems switching between space heating and hot water, boiler hybrids and older Y-plan style systems.
An actuator moves the internal port to send water to heating, DHW or sometimes a mixed position.
A one-way valve that prevents reverse flow.
Water circuits, DHW mains supplies, secondary returns, hydraulic layouts and some refrigerant circuits.
Forward pressure opens the valve; reverse pressure closes it to stop backflow or unwanted circulation.
A safety valve that opens at excessive pressure.
Sealed heating systems, unvented cylinders, refrigerant systems and heat pump packages.
When pressure exceeds the rated value, the valve lifts and discharges fluid to a safe route.
A pressure vessel with a gas side and water side separated by a diaphragm.
Sealed heating systems, chilled water systems and unvented DHW systems.
It absorbs expansion as water heats up, helping keep system pressure within safe limits.
A temporary or built-in connection used to fill or top up a sealed heating system.
Sealed heat pump, boiler and hybrid heating systems.
It connects mains water to the heating circuit through valves and backflow protection, allowing pressure to be restored.
The external unit that exchanges heat with outdoor air.
Air-to-water monoblocs, split heat pumps, air-to-air heat pumps and air conditioners.
A fan moves outdoor air across a coil while the refrigerant circuit absorbs or rejects heat depending on mode.
An indoor unit containing hydraulic and control components.
Split air-to-water heat pumps and some packaged systems.
It transfers heat from the refrigerant circuit to water, often housing pumps, valves, sensors, controller and backup heater.
Buried pipework that collects low-grade heat from the ground.
Horizontal ground source heat pump systems.
A water/glycol mixture circulates through buried pipe, absorbing heat from the ground before returning to the heat pump.
A deep vertical ground heat exchanger.
Ground source heat pumps where land area is limited or larger loads are required.
Fluid circulates down and up a vertical loop, exchanging heat with stable ground temperatures.
A source-side heat exchanger or intake arrangement using water as the heat source/sink.
Water source heat pumps using lakes, rivers, aquifers, wells or shared ambient loops.
Heat is exchanged with source water either directly through an exchanger or indirectly through an intermediate loop.
A secondary heat source used alongside the heat pump.
Hybrid heat pump systems, bivalent systems and some commercial plants.
It provides heat during peak loads, high-temperature demand, faults or control strategies where the boiler is temporarily more suitable.
The electronic control board or control system for the unit.
All modern heat pumps and air conditioners.
It reads sensors, runs safety logic and controls compressor speed, pumps, fans, valves, defrost and heating schedules.
Power electronics that vary motor speed.
Most modern heat pumps, air conditioners, VRF systems and variable-speed chillers.
It converts incoming power into a controlled frequency and voltage, allowing compressors or fans to modulate output.
A sensor that reports temperature to the controller.
Outdoor air, flow, return, cylinder, evaporator, condenser, discharge, suction and room locations.
Its electrical resistance or signal changes with temperature, allowing the controller to make decisions.
A device that measures or reacts to pressure.
Refrigerant circuits, water circuits, safety systems and control systems.
It sends pressure data or opens/closes a contact so the controller can protect the compressor and manage operation.
A sensor or switch confirming that water is moving.
Air-to-water, ground source, chillers, DHW circuits and hydraulic modules.
It measures flow rate or proves minimum flow, preventing operation when circulation is inadequate.
The user-facing device for temperature settings and schedules.
Most heating and cooling systems, from domestic heat pumps to commercial air conditioning.
It requests heating or cooling based on temperature, schedule and sometimes smart optimisation logic.
An electric resistance heater in the water path or unit.
Hydroboxes, monoblocs, cylinders and some exhaust air heat pumps.
It converts electricity directly into heat for backup, boost, commissioning, frost protection or exceptional demand.