Centralised Systems – Chilled Water
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Fan coil units serving each apartment and connected to a central air cooled chilled water (CHW) generation and distribution system is generally installed into apartment developments in South East Queensland in the following situations:
- Where the building height and subsequent vertical separation between indoor and outdoor units exceeds the refrigerant piping capabilities of VRF systems with condensing units located on the roof.
- Where the available roof plant area is too small to install individual VRF (or similar) systems.
- Where louvred plant areas for individual VRF (or similar) systems on each level of the building is not suitable.
- Where requested by the Developer.
Generally two (2) air cooled CHW generation machines, or chillers, and three (3) CHW pumps are installed for each building to provide the associated building’s cooling capacity whilst providing an agreed level of redundancy if one chiller fails. Chiller/s are generally located on the building roof.
Depending on the chiller/s cooling capacity and compressor type, refrigerant R410a or R134a is currently utilised by all reputable air cooled chiller manufacturers.
Heating is generally provided through electric heating elements at the indoor fan coil units.
The system arrangement includes:-
- Air cooled chiller/s consisting of compressor/s, condenser coils, evaporator, discharge fan/s and associated electronics, with optional drive (motor) technologies available for each component for increase energy efficiency.
Air cooled chiller (image courtesy AHI Carrier).
- Multiple indoor fan coil units, each consisting of a cooling coil, modulating CHW valve, electric heating element, supply fan/s, and associated electronics. In-ceiling ducted fan coil units are widely available, however other types such as wall mounted are limited in availability.
CHW indoor in-ceiling fan coil unit (image courtesy GJ Walker).
- Pumps, insulated CHW piping, valves, an expansion tank, a buffer tank and water treatment system for distributing CHW between the chiller/s and the fan coil units throughout the building.
- A CHW thermal energy meter for each apartment.
- A building management and control system (BMCS)
Unlike VRF systems, a CHW distribution system can be designed and installed to suit any building height or configuration.
Similar to VRF systems, apartment air conditioning control functionalities are managed at a control panel associated with each fan coil unit. However each control panel is also connected to a BMCS which operates the chiller/s, CHW distribution and/or electric heating elements based on cooling or heating demand from each fan coil unit.
The BMCS is required to collect data from the CHW thermal energy meters installed at each apartment and apportion the central CHW generation and distribution system’s power consumption based upon each apartment’s air conditioning usage. The BMCS automatically generates air conditioning CHW energy bills for distribution to each apartment owner / investor / occupier.
The air cooled central CHW generation and distribution system requires ownership, operation, maintenance and ultimately replacement to be managed as a common property facility by the body corporate. This includes entering into an air conditioning CHW energy supply agreement with each apartment owner / investor / occupier, with the bills as described above distributed and associated monies collected.
Each individual fan coil unit is connected to the associated apartment’s metered electrical distribution board, with the electrical energy consumed by the fan coil unit included in the apartment’s overall electrical energy consumption. Therefore for fan coil unit energy consumption, the apartment owner / investor / occupier is required to enter into a negotiated energy supply and billing arrangement directly with the apartment owner’s / investor’s / occupier’s electrical energy distributor of choice, and not with the body corporate.
An air cooled central chilled water generation and distribution system can be utilised to serve common area air conditioning systems through connection to associated fan coil or air handling units.