Thermostats and controls.

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Thermostats and controls

The right heating controls will let you keep your home at a comfortable temperature without wasting fuel or heat – so you’ll reduce your carbon dioxide emissions and spend less on heating bills.

If your home is heated by a system of water-filled pipes and radiators running from a boiler, you have a ‘wet’ central heating system, whether it is gas, LPG or oil-fired. Your full set of controls should ideally include a boiler thermostat, a timer or programmer, a room thermostat and thermostatic radiator valves (TRVs).

 How much can you save?

Whatever the age of your boiler, the right controls will let you set your heating and hot water to come on and off when you need them, heat just the areas of your home you want, and decide how warm you want each area to be. Here are the average savings you could make in a typical three-bedroom semi-detached home, heated by gas:

  • Install a room thermostat if you didn’t have one before: £70 and 280kg carbon dioxide a year.
  • Fit a hot water tank thermostat: £30 and 130kg carbon dioxide a year.
  • Fit a hot water tank insulation jacket: £45 and 170kg carbon dioxide a year.

You can also make savings by using your controls more effectively:

  • Turn down your room thermostat by one degree: save around £65 and 260kg carbon dioxide a year.

You can upgrade or install heating controls without replacing your boiler, and it’s a particularly good idea to think about this if your controls are over 12 years old. Room thermostats, for example, are much more accurate than they used to be.


 Temperature controls


Room thermostats

These prevent your home getting warmer than it needs to be: they will turn the heating on until the room reaches the temperature you have set, and then off until the temperature drops.

Room thermostats need a free flow of air to sense the temperature, so they must not be blocked by curtains or furniture, or put near heat sources.

Your room thermostat should be set to the lowest comfortable temperature – typically between 18°C and 21°C. Try turning your thermostat down a degree or two and seeing if you still feel comfortable. You don’t need to turn your thermostat up when it is colder outside: the house will heat up to the set temperature whatever the weather. It may take a little longer on colder days, so you might want to set your heating to come on earlier in the winter.

A programmable room thermostat combines time and temperature controls and allows you to set different temperatures for different times of the day. You can have different temperatures in individual rooms by installing thermostatic radiator valves (TRVs) on individual radiators.


Thermostatic radiator valves (TRVs)

Thermostatic radiator valves do not control the boiler: they just reduce the flow of water through the radiator they are fitted to when the temperature goes above a certain setting. Set them to the level you want for the room: a lower setting uses less energy and so will save you money.

Please note: We would not recommend using radiator covers because thermostatic radiator valves (TRVs) sense the air temperature around them and control the flow rate depending on what level they’re set at. Having a cover over the radiator means that the TRV is enclosed, which is likely to make it think that the room temperature is higher than it actually is – because heat will be trapped between the radiator and the cover.

If you already have a radiator cover that cannot be removed, then it is still worth using TRVs to control the temperature as much as possible, although the radiator will be more effective at heating the room space without the cover. If you feel the radiator is not hot enough at a particular setting, turn up the TRV.


Zone control

Save money by not overheating parts of your home that are unoccupied or need lower temperatures – bedrooms or rooms with lots of glazing, for example. You can have separate heating circuits with their own programmer and room thermostat (or programmable room thermostat) or set zones by using thermostatic radiator valves (TRVs).


Cylinder thermostat

If your hot water is stored in a cylinder, the thermostat will prevent it being hotter than it needs to be. Once the water has reached the temperature you have set, the heat supply from the boiler will be turned off.

Turning the thermostat higher will not make the water heat up any faster, and the water heating will not come on if a time switch or programmer has switched it off.

Cylinder thermostats are usually fitted between one quarter and one third of the way up the cylinder. They have temperature scales marked: you should set them at between 60ºC and 65ºC. This is hot enough to kill off harmful bacteria in the water, but it s also hot enough to scald. For extra safety consider installing a thermostatic mixing valve which will automatically ensure that hot water is at a safe temperature.


Boiler interlock

This is not a control but a system of wiring that turns the boiler off when neither the room thermostat nor the cylinder thermostat needs it. Without this the boiler can continue to ‘cycle’, wasting energy.


Boiler thermostat

Your boiler will usually have a dial on it, marked in numbers or from Min to Max. This sets the temperature of the water that will be pumped from the boiler through the radiators to heat your home. The higher this is set, the quicker and more effectively the system will heat your home. In fact, if this is not set high enough, when it is very cold outside your home may not reach your desired temperature.

If you have a room thermostat and a boiler interlock, you can set the boiler thermostat quite high, letting the room controls do their job. But set it lower if there is anyone vulnerable in the household who might hurt themselves by coming into contact with very hot radiators or pipes.

Your boiler control thermostat should always be set to a higher temperature than the cylinder thermostat. In most boilers, a single boiler thermostat controls the temperature of water sent to both the cylinder and radiators, although in some they are separate.


 Timing controls


Programmer or time control

This will automatically switch your heating off when you’re not at home, or when you can do without it, such as when you’re in bed.

Programmers allow you to set ‘on’ and ‘off’ time periods. Most models will let you set the central heating and domestic hot water to go on and off at different times. There may also be manual overrides. Check that the timer on the programmer is correct before you set your programmes. You may also need to adjust it when the clocks change.

Choose a cold evening and time how long it takes for your house to warm up from cold to a comfortable temperature – this is the warm-up time. Then turn the heating off completely and time how long it takes for the house to start to get uncomfortably cold – this is the cool-down time.

You can now set your timers including the warm up and cool down time. So, for example,  you can make sure that the  heating goes on with a warm-up time before you wake up and turns off before you leave the house. If you insulate your home, it will warm up more quickly and cool down more slowly, so you’ll save money on heating.

If you insulate your home, it will warm up more quickly and cool down more slowly, so you’ll save money on heating.

Set your water to heat up only when you need it: keeping it constantly hot uses energy. If your hot water cylinder or tank is well enough insulated, you may even find that the morning’s hot water stays hot enough to use in the evenings.