A system for controlling the humidity, ventilation, and temperature in a building, typically to maintain a cool atmosphere in warm conditions.
How does air conditioning work?
Air conditioners use chemicals (refrigerants) that easily convert from a gas to a liquid and back again. This chemical is used to transfer heat from the air inside of a building to the outside air.
The machine has three main parts. They are a compressor, a condenser and an evaporator. The compressor and condenser are usually located on the outside. The evaporator is located inside the building.
The working fluid arrives at the compressor as a cool, low-pressure gas. The compressor squeezes the fluid. This packs the molecule of the fluid closer together. The closer the molecules are together, the higher its energy and its temperature.
The working fluid leaves the compressor as a hot, high pressure gas and flows into the condenser.
When the working fluid leaves the condenser, its temperature is much cooler, and it has changed from a gas to a liquid under high pressure. The liquid goes into the evaporator through an orifice (a very tiny, narrow hole). On the other side, the liquid’s pressure drops. When it does it begins to evaporate into a gas.
As the liquid changes to gas and evaporates, it extracts heat from the air around it.
By the time the working fluid leaves the evaporator, it is a cool, low pressure gas. It then returns to the compressor to begin its trip all over again.
This continues over and over and over until the room reaches the temperature you want the room cooled to. The thermostat senses that the temperature has reached the right setting and turns off the air conditioner. As the room warms up, the thermostat turns the air conditioner back on until the room reaches the temperature.
What types of air conditioning systems are there?
Split AC Systems only have two units, one inside the building and the other outside. The units are joined together by interconnecting pipework and cables. These systems are usually used to condition the air in a single room.
Twin split systems contain two indoor units connected to a singular outdoor unit. A branching kit is used in the pipework to connect all units together. This type of system can be used in a large single room to distribute air flow better.
Multi split systems, again have a singular outdoor unit but can have up to five indoor units connected to it. Each indoor unit has its own pipework connected directly to the outdoor unit. These systems are used to condition the air in different rooms in a building, giving individual control of room temperature settings. Though only either heating or cooling can be used at any one time.
In packaged systems, all the main components are encased in one unit and are used for bigger applications than the split systems. The unit is usually located on flat roof tops and ducting is used to supply large rooms/whole buildings with conditioned air.
Heat Recovery VRF Systems
These systems are usually used in large buildings with many rooms and many occupants. They can simultaneously provide heating and cooling to different rooms when required. These systems are complex with sophisticated technology. A large condensing unit (or many linked together) is installed outside, with many indoor units connected to the pipework.
What is a Heat Pump?
Heat pumps are integral to an air-conditioning system, transferring heat from one environment to another via a refrigerant. Heat pumps also offer a cost-effective heating solution – and air source heat pumps are recognised as a renewable heat technology.
In cooling mode, heat pumps work by transferring the heat from a room or internal space to the outside air, thus cooling the inside area. In reverse, heat pumps can extract latent heat from the outside air (even when the temperature outside is down to -20°C) and pump it inside to heat indoor spaces.
How energy efficient are air conditioning systems?
An air conditioner’s efficiency is measured by the energy efficiency ratio (EER). The EER is the ratio of the cooling capacity (in kW) to the power input (in Kw). The higher the EER rating, the more efficient the air conditioner.
Air conditioning systems can be very energy efficient. Most new systems are given an EER rating of ‘A’, some can even be given an ‘A+++’ rating in both heating and cooling.
A systems efficiency also greatly depends on the installation. Correct equipment selection is vital, so a survey is strongly recommended before any installation work is carried out.
Once installed, regular maintenance will keep the system running as efficiently as possible.
Do I need my air conditioning system serviced?
It is recommended that an air conditioning system is serviced at least once a year, in many other instances, maintenance may be required two, three or four times annually.
In residential properties where a system may only be used for half a year, a service once a year may be sufficient. In commercial properties, such as office buildings, it may require two visits annually. In other instances, such as hotels and hairdressers for example, systems may require four visits annually to keep them running efficiently.
After a new installation, for warranty purposes, the manufacturer of the equipment may insist on regular servicing for up to three years.
The amount of refrigerant inside a system may also dictate how many maintenance visits are required annually. If a system contains over a certain amount of refrigerant, then it may need an annual leak test under the 2014 EU F-Gas Regulation. Larger systems may require six-monthly or three-monthly leak tests.
What is the 2014 EU F-Gas Regulation?
Fluorinated gases (‘F-gases’) are a family of man-made gases used in a range of applications. In this case, refrigerants in air conditioning systems. Because they do not damage the atmospheric ozone layer, they are often used as substitutes for ozone-depleting substances. However, F-gases are powerful greenhouse gases, with a global warming effect up to 23 000 times greater than carbon dioxide (CO2), and their emissions are rising strongly.
The European Union is therefore taking regulatory action to control F-gases as part of its policy to combat climate change.
F-Gas tests are therefore a mandatory requirement on systems that fall into the threshold for leak testing. Records of the leak test results must be kept.
My air conditioning system isn’t working – what should I do next?
If this unfortunate circumstance occurs, it is best to call in the experts. An engineer will need to attend to check on the system, but time and money can be saved by taking a few notes before making the call. Note the make, model and serial number of the faulty unit. Also, check on the controller, a fault code may be visible, make a note of this too. With any extra information, the attending engineer can be prepared to find the fault quickly or even fix the problem first time of asking.