About Indirect Unvented Cylinders
Unvented cylinders store water that is supplied directly from the mains water supply. The water is then heated within the cylinder using either electrical elements or through a boiler. Because the water is coming directly from the mains, it is of a high pressure and can be used to heat large buildings, offices or houses that have a heavy level of hot water usage.
In reference to an unvented heating cylinder, indirect and direct refers to how the water is heated within the cylinder itself. When considering a direct system, an electric immersion heater is used, but if it's indirect then a heat exchanger is supplied using a boiler. Unvented cylinders are often made from stainless steel, copper, or in some cases, glass lined steel.
The unvented water cylinder takes water directly from the mains water supply. Unlike a vented supply the pressure coming from the mains is strong, meaning you don't have to add a pump to your water system. Because of the high pressure you can get the hot water to high up positions within a building too, such as the attic. The indirect unvented cylinder allows for longer hot showers that are at a higher pressure. The coil within the indirect storage tank acts as a heat exchanger this heat exchanger is connected to a boiler that produces water for the central heating system. Put simply, the water needed for the central heating first passes through the indirect unvented cylinder in order to reach the required temperature.