A-Z of Air Conditioning Terminology

Meet the A-Z list of all the terminology you need to know about Air Conditioning.

Whether you work with air conditioners, or have one that you want to get to know a little better, this list will give you all you need to know about what is what in the air conditioning world.

❖ Accumulator

The accumulator temporarily collects refrigerant to prevent any backflow into the compressor.

❖ Air Handling Unit

In a ducted system, the central AHU contains the heating and cooling elements, as well as the blower, filters, humidifier, dampers and all the other regulating equipment that helps the unit run. On a roof, this unit is called an RTU, or rooftop unit.

❖ Chiller

The chiller part of the unit contains the primary cooling medium, which is the refrigerant, this removes heat from the secondary medium, which is often the water, as it goes through cycles of compression and evaporation. The secondary medium then later cools the air as it passes through the coils in other units around the building. Chillers are then cooled by fan-driven external air, or occasionally by water that circulates through a cooling tower.

❖ Compressor

The compression pushes the refrigerant through its closed cooling loop, there are variations of this that include screw or scroll compressors.

❖ Condenser.

Opposing the evaporator, the condenser is the hot side of an air-conditioning unit. This is where the refrigerant will condense and heat is then extracted in order to either disperse it into the environment, as is the case in a cooling tower. Or to recycle it for other purposes.

❖ CAV + VAV.

CAV systems supply ‘Constant Air Volume’, but they vary its temperature. On the other hand, ‘Variable Air Volume’ systems control the temperature by varying airflow and saving energy by running much slower when demand is lower.

❖ Damper.

At various points in the ducts to control the air, you will find dampers. These can be manual, but they are often auto-controlled to assure that the most efficient and economical flow of air is achieved, When composed of angles slats these are called louvres. In Similarity, devices may be placed where ducts branch, they’re called turning vanes.

❖ Diffuser.

Diffusers split air streams in a variety of directions in order to produce a balanced airflow. These are often located at outlet points. Outlet grilles can also be crafted to direct air in any direction.

❖ Economizer.

The comparison of heat content in air outside and inside, allows economizers to vary the intake of environmental air to maximize energy efficiency.

❖ Enhanced Capital Allowance.

Enhanced Capital Allowance is a government scheme rewarding businesses for investing in energy-saving equipment.

❖ European Seasonal Energy Efficiency Ratio.

A performance rating for products such as chillers. If you capture and reuse energy, the EER is amended by the ERE.

❖ Evaporator.

A component of the air conditioner, or heat pump where the cooling takes place.

❖ Fan Coil Unit.

A small indoor terminal unit that controls the temperature of a single room. They contain a fan, valve and cooling coil that is linked to a chilled water supply.

❖ Filters and Purifiers.

Remove particles from the airflow, keeping ducts clear and air safe to breathe. Charcoal filters can remove gaseous pollutants too. They trap particles and bacteria to ensure safe air quality.

❖ Heat Exchanger.

A heat exchanger transfers heat from hot to cold. They recycle waste energy to power other parts of the system.

❖ Heat Pump.

A compressor that moves heat from one area to another. They can heat one space while cooling another space.

❖ Monoblock Air Conditioners.

Self-contained devices that expel air outside through a pipe. These are easy to install but are not as efficient as split and ducted systems

❖ Outdoor Unit

In non-ducted air conditions, the outdoor condenser contains a compressor, fan, circuit board, and heat exchange coil. It pumps refrigerant from one or more indoor units.

❖ Refrigerants

These are chemicals that readily evaporate and condense in a useful temperature range. These can often be ammonia and carbon dioxide, or Hydrofluorocarbons. Most common refrigerants used for air conditioning include R12, R22, R32, R410A, R134, etc.

❖ Split System

Split ac systems use an outdoor condenser and an indoor terminal unit. They void the need for any ductwork. A single outdoor condenser links to a plethora of indoor units in different rooms, or even different apartments.

❖ Thermostats

Sensors that report the temperature of the air to the main unit where it’s used to switch on the supply of heating or cooling.

❖ Zoning

The independent control of areas with different goal temperatures of conditions to save energy. Each zone has a ‘unitary controller’. Regulations often require zoning of large commercial buildings.



Author: Gareth Whalley
Sharing my vast knowledge in the Air Conditioning and Mechanical services field especially in HVAC installation, service and maintenance across a broad range of sectors, including Healthcare, Education, Transport, Banking, Retail and Commercial developments.