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Is it a good idea to fit a timer to my electric boiler?


In general boilers are on all the time, so that you have warm water day and night. With the help of a timer, you decide when the water is to be heated, for instance only at night.

The timer is the most economical method provided that:

  • you have opted for a dual hourly rate meter with your electricity supplier and your meter has been adapted to this rate;
  • the boiler is big enough to supply you with warm water during the day.

An ideal solution…in certain cases

Choose the night rate.

Set the timer so that it produces hot water only during the night. This will enable you to use the cheaper night rate as recommended by your energy supplier.
To do this, you need a meter with a dual hourly tariff.
This does not apply to gas boilers, since there is no night rate for gas.

What about buying a timer? Take account of the capacity of your boiler.

A boiler often requires a high capacity. Reckon on about 2000 to 3000 watts.
But take care, because your timer has to be equipped for this. Otherwise, there’s a risk of fire!

Look at the timer packaging to see if it allows for the capacity of your boiler.  This is usually expressed in terms of a ‘permissible capacity’, e.g. 10 amps.
A quick calculation tells you immediately if this is sufficient.  Suppose that you have a 3000W boiler with 230V.

Boiler capacity / Number of volts = number of amps that your timer must tolerate as a minimum.
3000W / 230V = 13 amps.

The permissible capacity of your timer in this case must be more than 13 amps.

What about a three-phase boiler? Call upon the services of an electrician.

Does your boiler have a plug? If so, there’s no problem. You probably have a two-phase boiler. It is very easy to connect a timer to this type of boiler.
With a three-phase boiler there is no plug. The boiler is connected directly to your electricity circuit. To fit a timer on to this circuit requires professional expertise. You will therefore need an electrician in this case.

Does the water stay warm all day? Definitely!

Let us give you an example of a family where this system is possible. This family of four is out during the day and they use water mainly in the morning and evening.

In the morning the water, which has heated up over night, will be at a temperature of around 65 °C (the standard temperature set on most appliances). However, this is far too hot for a shower! In reality, you only use a small proportion of the warm water available, mixed with a large quantity of cold water, for a pleasant shower.

Tip: use a thermostatic valve so as to waste as little water as possible.

The warm water used for showers is replaced in the boiler tank by cold water. This will bring down the temperature in the boiler slightly. However, that’s not a problem, because the total quantity of water stays warm (hot) enough.

Boilers are very well insulated. When the family comes home again in the late afternoon, the temperature of the water will have dropped again somewhat, but the residual temperature (e.g. 40 °C) and the quantity of water is still enough to enjoy a relaxing bath in the evening.

Case by case

Of course, using a timer for your boiler depends on the quantity of warm water that you need and the size of the boiler.
Ask yourself the following questions to get a clearer picture:

  • Do you have a small 50-litre boiler or a far bigger one?
  • Do you live alone or are there six of you at home?
  • Is anyone at home during the day?

If you need a large quantity of water during the day, it may be that the volume of water heated at night is insufficient. But even then a timer can be advantageous! In that case, set the timer so that the boiler can also warm up for a while during the day. You then switch to the day rate to heat the additional quantity of water.

Be careful, because the day rate in the dual hourly rate is higher than the standard rate. So make sure that the water heated during the day is only used as a top-up.

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