Centralised Systems:
(Chiller units, Air Handling Units and Fan Coil Units)

Centralised systems: in which refrigeration equipment delivers cooling through air handling unit(s) and/or pumped water circuits. These may include constant volume (CV) systems, variable air volume (VAV) systems, systems using fan coil units (FCUs) or induction units, and systems using active or passive chilled beams.

Centralised air systems: cooled air is produced by a cooling heat exchanger in an air handling unit (AHU) and distributed to conditioned spaces through ductwork to grilles or diffusers, or to other terminal units, in the conditioned spaces.
The cooled air distribution systems may also include floor or ceiling plena. This category includes systems where air distributed through a centralised ducted system may also be cooled at active or passive terminal devices in the conditioned spaces. This cooling may be provided by the indoor units of split packaged and VRF systems where these are installed within the air distribution ducts.

Centralised cooled water systems: Cooled water is produced centrally and distributed to active or passive terminal devices in the conditioned spaces.
Active terminal units would include fan coil units, and fan assisted chilled beams. Passive units would include chilled beams (without fans) and chilled ceiling panels. Terminal units may transfer cooling to recirculated room air, to fresh air drawn locally from outdoors, or to air supplied through centralised ducted systems.

Water loop/reversible heat pump systems: systems with individual reversible water to air heat pumps in the treated space that draw or return heat from or to a common temperature controlled water loop (sometimes known as ‘versatemp-type’). Excess heat in the water loop is dissipated as necessary by a cooling tower (often a dry cooler), and an overall requirement for heat in the loop similarly provided by a central heat generator (fossil fuel boiler, electric flow boiler, or other central hat exchanger).

These types of systems are categorised generally as Level 4 and a full procedure that would be appropriate usually where systems are centralised and make use of plant rooms, air handlers, water circuits and more complex controls.

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