Summary: Learn how to replace an element, replace a single or twin element and set a thermostat.
Immersion heaters are designed to heat water. They are made up of a cylindrical copper tank with either a single or twin element inside and are fitted with a thermostat control.
Single elements are available in lengths ranging from 280mm (11in) to 800mm (2ft 7 ½ in). The longer elements screw into the top of the cylinder (top-entry) while the shorter elements are fitted as a pair through the side of the cylinder (side-entry). Both elements will have their own thermostat.
Twin elements have a short element at the top for heating small volumes of water quickly and a long element for heating the whole cylinder. Twin elements are controlled by a single thermostat.
If you notice a lack of hot water or that the water is slow to heat up, this could indicate a burnt out element or a build-up of limescale around the element.
Unscrew the immersion heater cover.
Make a note of which cores are connected to which terminals and use a screwdriver to disconnect them.
To control the temperature generated by the immersion heater use a screwdriver to turn the thermostat dial to the desired setting. In an area with hard water, the maximum temperature should be 60°C or up to 70°C in a soft water area.
If you have two thermostats, the one controlling the daytime temperature should be set between 50°C and 55°C.
Immersion heaters with two elements are sometimes fitted with a switch on the thermostat with two settings ‘sink' and ‘bath', but this type of unit does not allow for any variation of temperature for the two settings.
Use a screwdriver to turn the thermostat dial to the desired setting.
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