Utilisation of Ambient Air and Shallow Geothermal Energy - Renewable Energy: Technology, Economics and Environment - page 417

Some split system air conditioners can reverse the refrigeration flow by using a
four-way valve near the compressor (reversible systems). Such units can also
serve as space heating devices with air as heat source and air as heat sink. The in-
door unit becomes the condenser and the outdoor unit the evaporator (including
compressor). For the heating mode another expansion device is used. This means
that such machines have also two magnetic valves around the expansion unit that
allow the use of different expansion devices for heating and cooling. For the heat-
ing mode a water drain has to be placed on the outdoor unit that is led into the
room in order to prevent ice formation in the drain in winter. Additionally a de-
frosting mode for the outdoor unit is necessary.
Modern systems have remote control with programmable timer, variable speed
compressor and fans with inverter technology, adjustable louvers and are there-
fore very easy to use for the consumer. A typical split air-conditioning system for
cooling only application is shown in Fig. 9.17. The main advantages of such sys-
tems are outlined below.
− Low investment cost and moderate operating costs.
− Cheap, flexible and easy mounting (only two holes in the wall for the cooling
mode and an additional hole for the drainage of the outdoor unit for the heating
mode).
− Easy to use for the consumer.
− High reliability.
− Decentralised application.
− SPF of about 2.5 for the cooling mode /9-17/.
− Low space demand.

Indoor unit

Outdoor unit

15 - 18 °C

Evaporator

Compressor

24 - 26 °C

approx.
40 °C

Water
drain

Condenser

30 - 35 °C

Filter
dryer

Capillary
tube

Fig. 9.17 Typical split system air conditioner (cooling-only mode)

The disadvantages of split systems may be as discussed below.