The most economical settings for immersion heaters
Many homes in the UK, especially those with electric storage heaters have their hot water supplied by the main central heating boiler. But more often than not there will also be an electric immersion heater in the hot water cylinder.
In fact some homes are totally reliant on having their water heated by an immersion heater.
Some hot water cylinders may also contain two immersion heaters; one located in the top of the cylinder and one at the bottom. Commonly, the bottom heater comes on late at night and heats the whole system using cheaper off-peak electricity. The top heater is often used to provide additional hot water during the day when it is required, using the more expensive peak rate electricity.
Thermostats and Controls
Immersion heaters may also have different thermostats and controls to manage the central heating radiators.
These immersion heaters are likely to have two controls, one input and one output. The output setting controls how much heat is given out whilst the input control determines the amount of electricity the heater will use during the night, and how much stored heat will be available the following day.
You should set the output dial according to how much heat you require immediately, and the input dial according to how much heat you predict you will need tomorrow.
If the hot water runs out whilst you still need it, or if the weather turns chilly, you will need to turn the input dial up. If the weather turns hotter, or you find that your heater doesn’t run out of heat in the evening, you will be able to turn the input dial down, saving you money.
On the topic of saving money, if you turn the output dial to zero prior to going to bed or leaving your house, you will avoid wasting energy through heating empty rooms. As it takes a while for the heating to cool down, you can do this up to an hour before you leave your house or go to bed.
When the warmer weathers comes (if it does) turn the heater off at the wall. But always remember you will need to turn it on the day before you want them to come back on though, as they will need time to heat up.
Controls for Immersion heaters and how to use them most efficiently
- Cylinder Thermostat - Your hot water is stored in a cylinder; the thermostat prevents that water from reaching a higher temperature than you want it to. Once the water has reached the desired temperature, the immersion heater will switch off. These thermostats should be set between 60-65 Celsius. This is hot enough to kill off bacteria, but cool enough not to scald.
- Time Switch - A separate hot water time switch will allow you to heat the right amount of water at the right time, allowing you to take full advantage of the off-peak economy tariffs. Set your water to heat up when you need it. Keeping it constantly on will use more energy. Also, the better the insulation on your water tank, the less heat that will escape.
- Boost Switch - Most systems have a second, smaller heater at the top of the cylinder. This heater is activated by a boost switch. Use the boost switch to heat a small amount of water at peak times during the day.
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Written on behalf of 'Heat and Plumb' by Martin Lynas