A centralised hot water system is a setup where water is heated and stored in one central location before being distributed throughout a building to various taps and outlets.
Understanding Centralised Systems
Unlike systems that heat water on demand at each outlet (like tankless heaters), a centralised system typically involves a large hot water storage tank. This tank holds a significant volume of pre-heated water ready for use.
Key Characteristics:
- Central Location: The heating source (like a boiler or immersion heater) and storage tank are located in one place, often a utility room or basement.
- Storage Capacity: These systems are known for storing water in large quantities. As referenced, centralised hot water storage systems store water in large quantities (e.g. 150 litres or more).
- Distribution Network: Hot water is pumped or flows via pressure through a network of pipes to different points of use within the building.
Storage vs. Usage
A notable aspect of centralised storage systems is the potential difference between the stored volume and the amount of hot water typically used for individual tasks. The reference points out that water is stored in large quantities without being used in full. In fact, much smaller quantities are required for typical hot water situations: for example, as a rule, only 10 litres of water or less are required for flushing in the kitchen.
This highlights that while the system can handle high peak demand by having a large reserve, it often holds far more hot water than is needed for frequent, small uses.
How They Work (Basic Concept)
- Heating: Cold water enters the system and is heated by a central source (e.g., gas boiler, electric heater, heat pump).
- Storage: The heated water is held in an insulated storage tank.
- Distribution: When a hot water tap is opened, the pressure pushes hot water from the tank through pipes to the outlet.
- Replenishment: As hot water is drawn out, cold water enters the tank to be heated, maintaining the supply (depending on the system's recovery rate).
Components of a Centralised System
While specific components can vary, typical elements include:
- Water Heater (Boiler, Immersion Heater, etc.)
- Insulated Storage Tank (Cylinder)
- Pipework
- Pumps (in some systems)
- Thermostats and Controls
- Expansion Vessel (in sealed systems)
Advantages & Considerations
Centralised systems can provide a reliable supply of hot water, especially useful for buildings with high, simultaneous demand. However, the large storage volume means energy is used to keep the water hot, even when not being used, as mentioned in the reference.
| Aspect | Description |
|---|---|
| Storage | Large volumes (e.g., 150+ litres) stored centrally |
| Distribution | Via pipe network to multiple points of use |
| Usage Pattern | Caters to high peak demand; stores more than typically used for small tasks (e.g., 10 litres for a kitchen flush) |
Understanding the volume of water stored versus the amount used for typical tasks, as highlighted in the reference, is key to appreciating the nature of these systems.
