Types of system

Air conditioning is to control the temperature in the main, control the humidity and clean the atmosphere that we live in. To control the temperature we have to add heat (energy) when cold and remove heat (energy) when warm. This energy has to be transported from outside to inside (Heating) and from inside to outside (Cooling).

There are three main methods to transfer this energy:

Air Systems

This is where we use the air to carry the energy from inside to outside and vice versa. The use of Air Handling Units (AHU), or Roof Top Packages (RTP), to condition the air (temperature, humidity sometimes), filter and refresh the air and send it through ductwork to the occupied space where the conditioned air will heat or cool the space as required and return via return air ducts back to the AHU or RTP.

Air Handling Units contain a cooling coil (connected to a chiller or condensing unit) a heating coil (connected to boilers or electric heaters) filters and circulating fan(s). Roof Top Packages contain refrigerant cooling cycle, heating coils (connected to boilers or electric heaters), filters and circulating fan(s).

Water Systems

In these systems water is used to carry the energy from inside to outside and vice versa.

The use of a chiller (on roofs or plant rooms) to cool the water which would be circulated via circulating pumps to the occupied space where it will be passed through fan coils (terminal units) which circulate room air over the coil, hence absorbing unwanted heat. The use of boilers (in plant rooms) to heat the water (separate circuit from cooling) which would be circulated via circulating pumps to and back from the occupied space where it will be passed through the same fan coil which circulate room air hence adding heat to the space.

Water Systems only control the temperature. Filtering of the air is normally carried out through the indoor fan coils (terminal units).

Ventilation is normally carried out through a separate system with a range of AHU and ductwork distribution system (smaller than air systems) which can be localised to the air-conditioned space.

Refrigerant Systems (known as Extended Direct Expansion or DX Systems)

In these systems refrigerant is used to carry the energy from inside to outside or vice versa. The use of outdoor condensing units (can be reverse cycle heat pump for heating) cool the refrigerant and sends it through refrigeration small bore pipe work to indoor fan coils (terminal units) where it will expand to lower the temperature of the refrigerant in the pipe, hence room air when circulated over the coil will lose its unwanted heat. Heating is achieved via the same outdoor unit by reversing the cycle or utilising a third pipe to carry hot refrigerant to the indoor unit to provide heating. Filtering of the air is normally carried out through the indoor fan coils (terminal units). Ventilation is normally carried out through a separate system with a range of AHU and ductwork distribution system (smaller than air systems) which can be localised to the air-conditioned space.