Un-vented hot water heating systems




Un-vented hot water heating systems

		When an un-vented hot water system is installed both the hot and the cold water supplies within the dwelling, deliver water at the taps or shower outlet at mains water pressure. Cold water from the mains is delivered to the base of the cylinder, the water is heated, then when a tap or shower is turned on the mains water pressure pushes the hot water out.


	To allow the water that is heated in the cylinder to expand as it is heated, an internal or external expansion vessel is used; a pressure relief valve is also fitted should the vessel fail. An un-vented hot water storage cylinder can be heated directly via an immersion heater or indirectly by most heating systems providing it is not a solid fuel burning appliance They are ideal where high performance is required or in multi story properties where it would be difficult to gain the necessary head of water via a cold water storage tank to feed taps on the upper floors.

Advantages

Balanced pressures at hot and cold taps.

High performance showering throughout the house.

High pressure and hence flow rate of hot water.

Fast filling baths.

Potable (drinking) water at all taps.

No cold water storage therefore no contamination.

Quicker to install Quiet running Fast recovery (typical 15-20 mins for 125L)

No fear of frozen loft pipes

Disadvantages

No storage back up if mains water fails.

Poor mains water pressure will cause poor performance.

Need for discharge pipe (overflow) Requires high level of maintenance





		Up until now, installers and specifiers have had two choices when it came to unvented hot water cylinders. The first is the 'standard' system, where an external expansion vessel needs to be connected by the installer. The second uses an internal air bubble, which removes the need for the vessel, but introduces the disadvantage of regular servicing to maintain the air bubble. Now there is a third choice - the DPS Amazon unvented hot water cylinder Click here for details