Information Sheet


Every radiator heating system, whatever the heat sources gas, diesel, heat-pump etc, your full set of controls should ideally include a boiler thermostat, a timer or programmer, a room thermostat and thermostatic radiator valves (TRVs).

With underfloor heating systems you won’t have TRV’s in each room but room thermostats instead.

Controls can take many forms from 230v to 12v to wireless, from standard dial thermostats to smart stats to weather compensation.

The more advanced control systems for domestic central heating, generally known as smart heating controls allow you to manage your heating controls remotely from a computer, tablet or smart phone, and many incorporate other advanced features to control your heating in more sophisticated way. Some can learn from your previous choices and make adjustments for you, while others use automation and optimisation features to help determine exactly when to turn the heating on.

One clear advantage of a smart heating control system is that you can make changes remotely if your plans change – for example, you can change the time that your heating comes on if it turns out you will be home sooner or later than you thought.

Whether a smart controller will save you money, and whether it is right for you, will depend on your lifestyle, how you currently control your heating and whether you prefer using an app to using a traditional controller.

Whichever type of control system you use they have the benefits of:

Reducing your carbon dioxide emissions.

Save money on your heating bills by installing and using your controls efficiently.

Allow you to schedule your heating and hot water to go on and off when needed.

Control areas of your home to heat and the required temperature for each room, rather than heating a whole house at the same temperature.

Room thermostats

These prevent your home from getting warmer than necessary. They 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 and 21 degrees.

You don’t need to turn your thermostat up when it is colder outside; the house will heat up to the set temperature regardless. 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 or in the case of Underfloor heating (ufh) you would have a programmable thermostat in each room.

Thermostatic radiator valves (TRVs)

Thermostatic radiator valves do not control the boiler; they reduce the flow of water through the radiator which 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.

We do not recommend using radiator covers because 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 the TRV is enclosed, which is likely to make it think that the room temperature is higher than it actually is.

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. If you feel the radiator is not hot enough at a particular setting, you can turn up the TRV.

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’ and waste 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. The higher this is set, the quicker it will heat your home. In fact, if it is not set high enough, when it is very cold outside your home may not reach the desired temperature. However, condensing boilers work more efficiently when the water returning to the boiler is below 55 degrees, so it can be better not to set the temperature too high.

If you have a regular boiler with separate hot water cylinder, your boiler thermostat should always be set to a higher temperature than the cylinder thermostat, otherwise the hot water cylinder will never get up to temperature. If you have a combi boiler you will probably have two dials – the one with a radiator symbol controls the output to the radiators and you can set this at the best point for your heating without it affecting the hot water temperature.

In the case of heatpumps the running temperature will be a lot lower normally in the region of 40 degrees to ensure the heatpump is working at its most efficient level which is way heat pumps are not usually used for radiator heating system but can be a good choice for ufh.

Weather compensation

When the weather is cold you need your boiler stat to be set to a high level to make sure your house can get warm enough. If the weather is milder you could turn the boiler stat down and still be warm enough. This will make the system more efficient, especially if you have a condensing boiler. A weather compensator does this for you automatically by measuring the outside temperature and adjusting the boiler thermostat temperature as required.

Programmer or time control

This will automatically switch your heating off when you’re not at home, or when you don’t need 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 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. 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 faster and cool down more slowly and hold the heat more efficiently, so you’ll save money on heating.

In the case of ufh within a concrete floor the heating is not turned off but will be operated with a comfort and set back level of temperature to ensure the concrete slab retains its heat at all times.

Zone control

Most households want to heat different rooms at different times of the day. You can do this by turning individual radiators on and off at different times, but lots of people don’t get round to these.

Zone control does this for you automatically by having separate heating circuits for different parts of the house, with a separate programmer for each circuit. If you’re fitting a new heating system, then you may want to consider zone control to help you keep heating costs down. And if you’re fitting it in a large house, you may be required to have two separate zones to meet  your lifestyle.

Programmable TRVs

These are temperature controls for individual radiators, just like standard TRVs, but with timing control as well. So you can set each radiator to come on at different times, and heat each room only when you want to. However remember that TRV’s are not wired and therefore don’t directly control the boiler and only work whilst the heating is control by a wired time control or thermostat.


An optimiser works out how long it takes your house to heat up and turns the heating on at the right time so your house will be up to temperature just in time for when you need it. For example, if you get up at 7:30 in the morning you can set your programmer to 7:30am, and your thermostat to whatever you choose, and the optimiser will work out when to fire up the boiler so the house is up to the temperature you set by 7:30am. In colder weather, it will fire up earlier and in milder weather it will wait a bit, saving you energy and money.

Optimisation is one of many features that may be available if you fit a smart heating control system.


An automated heating control system works out whether and when to turn the heating on based on whether there is anyone in the building, or whether you are approaching the building. It may use sensors in the home or it may track your phone’s location to decide when to turn the heating on. Automation is available as part of some smart heating controls, and generally includes an optimisation function to help decide when to turn the heating on.