A copper hot water cylinder works by storing water under mains pressure, heating it, and then using the incoming pressure to push the hot water out when a tap is opened. This provides a supply of hot water at mains pressure.
Here's a breakdown of the process:
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Filling: The cylinder is connected directly to the mains water supply. As such, it is constantly filled with water at the same pressure as the mains.
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Heating: The water inside the cylinder is heated using one of several methods:
- Immersion Heater: An electrical element (immersion heater) located inside the cylinder heats the water directly.
- Indirect Heating (Central Heating System): Hot water from a central heating boiler (e.g., gas boiler) circulates through a coil inside the cylinder, transferring heat to the surrounding water. This coil is often referred to as a heat exchanger.
- Solar Heating: Solar thermal panels on the roof collect heat from the sun. This heat is then transferred to the water in the cylinder via a heat exchanger.
- Heat Pump: An air source or ground source heat pump may also be used to indirectly heat the water within the cylinder.
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Storage: The cylinder is insulated to minimize heat loss and maintain the water at a desired temperature.
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Hot Water Delivery: When you open a hot water tap, the incoming mains pressure forces the stored hot water out of the cylinder and through the pipes to the tap. The cold water entering the cylinder from the mains pushes the heated water out from the top of the tank.
Key Components and Functionality:
- Pressure Relief Valve: This valve is a crucial safety feature. If the pressure inside the cylinder exceeds a safe limit (due to overheating, for example), the valve will automatically release pressure to prevent the cylinder from bursting.
- Thermostat: This regulates the water temperature. It switches the heating element (or heating input from another system) on and off to maintain the desired temperature.
- Insulation: Thick insulation around the cylinder minimizes heat loss, improving energy efficiency.
- Sacrificial Anode: This protects the cylinder from corrosion. The anode is made of a more reactive metal than copper, so it corrodes instead of the cylinder itself. It requires periodic replacement.
In essence, a copper hot water cylinder acts as a storage tank for heated water, relying on mains pressure to deliver that water on demand.
