Heating controls

A timer or programmer allows you to control when your heating and hot water comes on and when it goes off.

This is useful because it means you can programme your central heating to fit around the way your home is used. If you’re not at home or don’t require heating at night, then you can programme the heating system to switch off during these times.

Older programmers are simple timers that only operate once a day, but modern programmers offer options to control multiple on and off periods. More sophisticated programmers now exist that are usually referred to as smart heating controls, which could offer more convenience and energy savings.

Depending on how your central heating system was installed, programmers are either:

• Single channel – for combi boilers. This only controls central heating as hot water is provided on demand.
• Two channel – for system or regular boilers, controlling heating in a single zone and hot water, or combi boilers controlling two separate heating zones (eg upstairs / downstairs).
• Three channel – for system or regular boilers, controlling hot water and two separate heating zones.

How to set your programmer to save energy

The programme you set will be unique to your heating needs, but here are a few tips if you’re looking to save energy.

1. Plan ahead

The less often you have the heating and hot water on, the more money you will save. Think carefully about when you need the heating, and any periods in the day when you don’t need it – for example, if everyone in the home is out at work or school, the heating can be off. Some programmers allow you to set different programmes for different days, so you can match it to your schedule.

2. Include warm-up and cool-down times in your programme

It takes time for a house to heat up after the heating switches on and will take a while to cool down after the heating is switched off. Generally, the average house will take about 30 minutes to heat up or cool down, but every home is different.

To find out your home’s ‘warm-up’ and ‘cool-down’ times, you could 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 programmer, 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, saving you money on heating.

3. Don’t forget hot water

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

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 should not be blocked by curtains or furniture, or placed near heat sources that could give them false readings.

Your room thermostat should be set to the lowest comfortable temperature, which for most is between 18°C and 21°C. If you only have a single room thermostat for the whole house, for every degree you increase the temperature, it will increase the heating bill by about 10%.

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 in a single unit and allows you to set different temperatures for different times of the day. Some heating systems may use two programmable thermostats (upstairs and downstairs) rather than a single programmer for the whole house.

Thermostatic radiator valves (TRVs) do not control the boiler; they control the flow of hot water through the radiator they are fitted to. They work by sensing the air temperature around them. If the room is warmer than the setting on the TRV, the valve will close a little, reducing the volume of hot water flowing into the radiator. If the room temperature is lower than the TRV setting, the valve opens, increasing the flow of hot water into the radiator.

A radiator cover can prevent the TRV getting an accurate temperature reading. Warm air, heated by the radiator, can get trapped under the cover, and the TRV can read this thinking the room is warmer than it is. We do not recommend having radiator covers, if possible.

TRVs can be adjusted to different settings by twisting them clockwise or anti-clockwise. They are usually marked with a scale from 0 – 6, where zero (0) is off and six (6) is fully open. Aim for the lowest setting that keeps the room to your desired temperature. A lower setting reduces the volume of hot water, using less energy and saving you money. If you’re not using a room, TRVs can also be used to either turn the radiator off completely or maintain a minimum temperature to keep the room just warm enough to prevent damp.

Many companies offer more advanced control systems for central heating, known as smart heating controls. They do everything that conventional controls do, with a programmer (timer) to control when the heating is on or off and using thermostats to control the heat in your home. However, smart controls are connected to the internet and offer more functionality.

Some of the more sophisticated features they can offer include:

• Simple and easy to use time and temperature controls with user friendly interfaces, making it easier to check and change the on/off periods for heating and hot water.
• Allowing you to turn the system on or off and change the temperature using your smartphone when you’re not at home.
• Learning your habits and adjusting controls to match, for example turning up the thermostat in the evening when you’re relaxing, detecting an open window (by a sudden drop in temperature) and turning the thermostat down or heating off, or heating the hot water ready for when you’re most likely to take a shower or bath.
• Track where you are using your smartphone location, known as ‘geo-fencing’. When you’re returning home from work, the heating system will turn on and heat the house or hot water in time for your return.
• Other advance control functions such as load compensation and weather compensation.

Even if you don’t think you would use features such as geo-fencing, having a system that can learn your habits and adjust times to minimise energy use requires very little input from you once the system has been set up.

Whether smart heating controls will save you money will depend on your lifestyle and how you currently control your heating. Studies suggest that while they can save money, it may take some time to pay for their upfront cost as they can be quite expensive.

Traditionally, hot water cylinders were heated whenever the heating was on, with no time or temperature control. If you don’t already have one, adding a hot water cylinder thermostat could significantly reduce the amount of energy you use to heat hot water.

The thermostat prevents the cylinder becoming hotter than it needs to be. Once the water has reached the set temperature, the heat supply from the boiler will be turned off. Turning the thermostat higher will not make the water heat up any faster.

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 60°C and 65°C. This is hot enough to kill harmful bacteria in the water, but be careful, as it’s also hot enough to scald.

Your boiler is fitted with its own thermostat, which sets the flow temperature of the water that is pumped from the boiler to the radiators.

The water cools as it flows through the radiators before returning to the boiler. The temperature at this point is known as the return temperature.

Turning down the flow temperature also reduces the return temperature. This makes the boiler more efficient, which will save you energy and money. But you need to make sure that this won’t impact your comfort levels or put anyone vulnerable living in your home at risk.   

Another important thing to know is that the higher the flow temperature is set, the quicker your home will heat up. So, if it’s not set high enough then your home may not warm up quickly enough to the temperature you want when it’s cold outside.

The boiler thermostat is on the boiler unit. It might be a dial that’s marked in numbers or marked on a scale from minimum (min) to maximum (max). It might also be controlled by a couple of buttons with the temperature shown on a digital display.

If you have a combi boiler, there’ll be two controls: one for the radiator flow and one for the hot water that goes to your taps. On a combi boiler you can turn the flow temperature down as much as you like as long as your home stays warm enough.

If you have a regular boiler with a separate hot water cylinder, there’s only one control for both your radiator flow and hot water taps. You need to make sure the temperature is set high enough so that you have hot water. This should be no lower than 65 degrees so that it can heat your cylinder to 60 degrees. This is very important to prevent the growth of harmful bacteria.

You can read more about turning down your boiler’s flow temperature in our blog.

A lower boiler thermostat temperature reduces the amount of energy used, which could save you money and lower your carbon emissions. When the weather is mild, you could turn the boiler thermostat down and still be warm enough. However, when it gets colder, the boiler thermostat may need to be increased again to make sure your home can get warm enough. A weather compensator does this for you automatically by measuring the outside temperature and adjusting the boiler thermostat temperature as required.

Before your heating turns on, the house may be very cold. To heat your home quickly, the boiler thermostat can be set high, so the water temperature sent to your radiators is higher. A hotter radiator heats the room more quickly than a cooler radiator.

Later in the day, your home may already be warm, and you may only need to raise the temperature by a couple of degrees. With the boiler thermostat still set high, the radiators will still be very hot, and you could risk overheating the home as you heat the room too quickly. A load compensator measures the difference between the internal air temperature and what has been set on your room thermostat, adjusting the boiler thermostat to prevent overheating.

If you have a system or regular boiler with hot water cylinder, then you should have a programmer, room thermostat and cylinder thermostat. These controls should be connected to create a ‘boiler interlock’, which means the boiler switches off if the heating and hot water thermostats have reached their set temperatures. Without an interlock, the boiler can continue to run even if the heat is not required. Building regulations require all new and replacement systems to be interlocked.

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

Zone control does this for you automatically by having separate heating circuits, each with their own time programme, for different parts of the house. Commonly, this includes one zone upstairs and another downstairs, but you could have more zones. For example, homes with underfloor heating sometimes have a room thermostat for each room, effectively meaning each room has its own zone.

If you’re fitting a new heating system, then you may want to consider zone control to help you keep heating costs down by avoiding heating rooms you’re not using. If your home is large enough, zone control may be required to meet building regulations.

If you’re not fitting a new system, it may be impractical to convert your existing pipework. In this case, you may want to consider programmable TRVs.

These are temperature controls for individual radiators, just like standard TRVs, but with timing control as well. They allow you to set each radiator to come on at different times and heat each room only when you want to. Some models can be connected via Wi-Fi to smart heating controls, allowing you to create a new zone for each room.