So what are the main types of air conditioners and the differences between them? Below is a list of the most common forms of HVAC systems with a little information about each type. So before you purchase your air conditioner, make sure you have a read to determine which type you are after.
Ducted Reverse Cycle / Refrigerative:
Ducted reverse cycle (or refrigerative) units are the best units available on the market. They can both heat and cool and you can get quite an accurate temperature with them. They are closed systems (that is you keep the doors and windows of your home closed).
They basically work by compressing and decompressing a gas which then either heats or cools the air. The air is blown out by a series of diffusers (or grilles). This airflow then circulates the house and then is sucked back up by a return air filter where it is either re cooled or heated and sent out again.
The main benefit of reverse cycle ducted systems are that you can have the ability to cool or heat all rooms in your house (although not usually all rooms at the same time). You will often break the house into a series of zones whereby you can run about half the zones at any one time. Reverse cycle systems provide superior comfort and performance over many years.
The disadvantages of reverse cycle ducted systems are that they are expensive upfront to purchase. A basic reverse cycle ducted system will cost around $7,000 (US) or $10,000 (AUS) for a basic single storey 4 bed 2 bath home (supplied and installed). They are also more costly to run than the other type of air conditioners available. Another drawback is that some people find the air that is recirculated can become stale. To overcome this a fresh air inlet can be added that brings in a percentage of fresh air when the system is running. Commercial projects must have this fresh air system included in all ducted reverse cycle systems.
Ductless Air conditioning / Reverse Cycle Ductless / Wall Split air conditioners:
Ductless air conditioners (or wall splits) are based on the same principles as ducted reverse cycle but they only occupy a single room. Ductless air conditioners consist of a head unit that sits in a room. A series of pipes and cables connect this unit to a compressor that sits outside.
The benefits of ductless air conditioners is that they can both heat and cool and provide good temperature control. They are quick and easy to install and are readably available. These ductless air conditioners are also cheap although once you start installing more than 3 or 4 it becomes more economical to purchase a ducted system. A ductless system can start at around $1,200 (US) $1,500 (AUS) for a small bedroom supplied and installed.
The disadvantages of having a ductless (wall split) unit is that they can only cool/heat the room that they are in. These units cannot be relied upon to transfer the air conditioned air to rooms adjoining the room the air conditioner is located in. Like the ducted reverse cycle units they can also make the air stale. The blow of the unit also often blows directly on people which can be uncomfortable.
Be careful to purchase a heating and cooling unit. Some ductless units are sold with cooling only features.
Box Units:
Box units are cheap to buy but a little nasty. A box unit is basically a box that sits either in the window frame or in the wall. Half of the unit sits outside the room whilst the other half sits inside the room. This compressor that sits outside is the mechanics behind the cooling and heating.
The indoor section is basically half a box with buttons where the air flows from. These units can only cool/heat the room they are located in.
The advantage of these units are they are cheap and suited to locations that only need air conditioning for a few days of the year.
The disadvantage of these units are they can be noisy and not very powerful. They also look quite ugly sticking out of the wall both from the inside and the outside. They will also only work in the room they are located in.
Evaporative Coolers:
Evaporative coolers are the big boxes you see on people roofs. They work by drawing in air to run over a series of wet sheets that look like hay bails. It works in the same way that wind over an ocean causes a cooling effect. The air is sucked in by a big fan located inside the box unit on the roof. Once the air goes into your house it rushes through your house and out any open doors or windows.
Many commercial properties, shops and factories have evaporative air conditioners due to their cheap price and ease of use. You can often here a whistling noise when opening the door of a shop caused by the pressure built up by one of these systems.
Evaporative air conditioners are one of the cheapest forms of air conditioners available. For a few cents an hour they can cool an entire home at once.
The disadvantages of evaporative air conditioning units are that they will not work in humid weather. Once the air is saturated with moisture, the evaporative unit cannot add any moisture so the system will stop cooling. They can also bring a lot of dampness into your home which can cause mould build up. They also have no temperature control so the unit runs either on or off.
You also have to have doors and windows open to use the system which can be a security concern. If the system is not used for an extended period of time, professionals need to be called to flush the system as evaporative coolers can easily transmit legionnaires disease.
Portable Units:
Portable units are the cheapest of all units however can be quite expensive to run. These are the units offered at retail stores for a few hundred dollars.
These units will only provide minimal heating/cooling and are best avoided.
Fans:
Fans are the cheapest form of cooling. Fans are readably available in almost every store. They can be a simple pedestal fan or a fancy roof fan.
They will provide adequate airflow with minimum cooling and are cheap to run. However, do not rely on a fan on a hot day or a long humid night.
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