Search all WA Government Sites Print this page	Refrigerative air conditioners use the same operating principle as refrigerators, they "pump" heat from one place to another. Like refrigerators, they have two connected coils - an inside coil and outside coil. The coils are connected by pipes filled with refrigerant which is pumped around the circuit by a compressor. As warm air passes over the indoor coil, heat is transferred to the refrigerant passing through the coil and pumped to the outdoor coil where it is dissipated into the atmosphere. This is the reason why air conditioners are also called heat pumps. Some refrigerative air conditioners also work in reverse to provide heat in winter. Rather than making their own heat from electricity, they use the electricity to pump heat from outside the building to inside. Even on fairly cold days, energy can still be extracted from the outside air and pumped inside. However, reverse-cycle air conditioners may perform poorly when the temperature is less than about 4ºC (unless optimised for these conditions). Refrigerative systems dehumidify as well as cool the air. This feature makes them highly suitable for hot, humid climates like the coastal regions of the Kimberley. Appropriate system size is particularly important with refrigerative air conditioners as choosing a system that's too small won't provide effective cooling and choosing one that's too large will result in frequent cycling (turning on and off), wasting energy and money and increasing the system's wear and tear. An oversized system may also be less effective at dehumidifying the air. Refrigerative air conditioners should be sized based on output capacity. The output is normally expressed in kilowatts (kW). If you're considering purchasing a room unit, an approximate guide is to allow 0.125 kW per square metre of floor area to be cooled in living areas and 0.08 kW per square metre of floor area in bedrooms. This guide applies to standard 2.4 m high ceilings with insulation. For example, a living room with an area of 30m2 will require an air conditioner with an output of around 3.75 kW, while a bedroom with the same floor area will require an air conditioner with an output of around 2.4 kW. As appropriate sizing depends on a number of other factors besides the area of room to be cooled, make sure you consult an air-conditioning specialist before purchasing your system. Your specialist will be able to give you a precise calculation of size based on your own specifications. When sizing your system it is important not to confuse the output capacity with the input capacity or coefficient of performance (COP). The COP of an air conditioner indicates how many units of heat are removed by the air conditioner per unit of electricity consumed. For example, an air conditioner with a COP of 2.5 will pump 2.5 kWh of heat outside for every unit (kWh) of electricity used. Typically, COPs vary from a low of about 1.7 to a high of about 3.3 for domestic air conditioners. For air conditioners capable of heating, different COPs apply for the heating mode and are usually between 2.0 and 3.2. Air conditioners with a high COP for cooling do not necessarily have a high COP for heating, although this is often the case. Portable units Small, portable units cool one room at a time and can be wheeled from room to room. A connection to the outside is required to remove the hot air. Some units can be placed in an open window so the hot coil is outside while other types have an internal hot coil and a flexible air hose which can be placed out a window or door. Fixed or fascia units Fixed units can cool larger areas and come in two main types - single units and split systems. Single units are mounted through a wall or window with the hot coil on the outside and can only really cool the room in which they are situated. As the pumps and fans are all in one location, they can be quite noisy. Most can be adjusted to either fully recirculate air or to incorporate a portion of fresh air from outside. Split systems have the cool coil inside a room and all the other equipment located outdoors up to 15 metres away. This makes them much quieter indoors than single units. Some split systems can cool more than one area but these are more expensive. Split systems generally do not enable fresh air to be incorporated in the air flow, instead relying on 100% recirculated air. Ducted systems These systems can cool a whole house by supplying cool air to multiple outlets. A good system will have a zone arrangement so that cool air can be supplied to only those areas required (for example, living areas during the day and bedrooms at night). This can significantly reduce the amount of energy consumed. Ducted systems can be roof or ground-mounted and are usually split type systems with the hot coil and fluid pumps outdoors and a cold coil situated inside the ducting. Typically air is drawn from inside the house and then cooled and recirculated. Some systems allow fresh air to be mixed with the recirculated air. Take care to plan the layout of ducts, thermostats, sensors, timers and other devices to get the best performance and efficiency from your system. Operating tips When operating a refrigerative air conditioner, always ensure windows and doors are closed so the cool air does not escape. Ensure that the outside coils, pumps and other equipment are in a cool place and well ventilated . This helps improve the unit's performance as it does not have to pump heat up such a high "temperature hill". Refrigerative air conditioners should also be kept clean and protected from the weather, as dirt will decrease their effectiveness and efficiency. If not used for extended periods, covers should be placed over the compressors, air intakes, cooling coils etc. to keep dirt and bugs out. With cooling only systems, ducts should be closed during winter to prevent warm air from leaking out of the house. Creating air movement through the house can make temperatures of 24-27ºC quite comfortable, so set the thermostat to ensure that no active cooling occurs below this level and circulate air with the air conditioner's fans or other fans. This will lower the operating cost - each degree you lower the thermostat, energy consumption increases by about 10%.
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