Wolseley STREAMLINE 10L 3kW OVERSINK COMP OFFER

Electric water heaters provide hot water close to where it is used, without relying on a boiler or central cylinder. This category covers under-sink and over-sink storage heaters, instantaneous heaters, and larger vented and unvented heaters of up to about 120 litres, rated from 1 kW to over 10 kW.

Types

• Vented or open-outlet heaters: the outlet acts as the vent, so use only the vented taps or spouts made for them and never block the outlet. Some water may drip from the spout as it heats and expands.
• Unvented heaters: run at mains pressure and feed ordinary taps. They need safety devices such as a pressure relief valve; if the mains pressure is above the maker's range, a pressure reducing valve is needed, and sometimes an expansion vessel.
• Instantaneous heaters: heat water as it flows, with no store; small ones serve a hand basin and multi-point units feed several outlets.

Regulations

In England, a heater storing 15 litres or less with suitable temperature and pressure safety devices will generally meet Part G, and fitting it is not notifiable if the electrical work is not notifiable either. An unvented system storing more than 15 litres is notifiable building work and must be installed by a competent person (G3); an installer registered with a competent person scheme can self-certify it, otherwise building control must be told before work starts. Heaters and fittings on the water supply must be suitable under the Water Supply (Water Fittings) Regulations 1999.

Electrical supply

In England, some electrical work in homes, such as a new circuit, is notifiable under Part P of the Building Regulations, so use a registered competent person or notify building control.

For cylinders and other hot water options, see cylinders and water heaters; for isolating valves, see valves.