Heating control analysis

What do we mean by heating control?

Heating control refers to the settings used to heat the school effectively while it is fully occupied. Getting the heating control right for your school can save money and carbon very quickly as well as improve the learning environment for students. 

There are a number of things to consider when it comes to heating control:
  • Central heating operating times - the settings which tell a school’s heating to come on in the morning and go off in the evening.
  • Seasonal control - the settings which ensure that the school’s heating doesn’t come on in warmer weather.
  • Heating set temperatures - the temperatures that are suitable for various areas around the school
  • Frost protection - the settings which protect the school’s pipes from freezing during very cold weather, without the need to fully heat the school.

More advanced users can also review the advanced thermostatic control of their boiler, which is how well a heating system is managed so that the amount of heating directly follows the outside temperature.

What are central heating operating times?

Central heating operating times are the settings used to make a school’s central heating come on in the morning and go off in the evening.

One of the easiest ways to save your school money and reduce its carbon footprint is to make sure you're only heating the school when it needs to be warm.  Heating needs to come on at a suitable time for the school to be up to temperature when school starts, and be switched off again about half an hour before school closes. 

Many schools have their heating coming on too early in the morning. Generally heating boilers shouldn’t be turning on before 5am in cold weather and 7am in milder weather. If your school heating comes on before this, you should be able to make changes to the heating controls to save energy and lots of money.

If your school has underfloor heating, it may take a few hours longer to warm up. However, many schools with underfloor heating keep it running 24 hours a day, which is unnecessary.

Heating set temperatures

A 1°C decrease in temperature on the thermostat leads to about a 10% decrease in gas consumption. 

The best temperatures for schools are: 
  • Normal classrooms: 18°C
  • Corridors: 15°C
  • Areas with high levels of activity (e.g. sports halls): 15°C
  • Areas with low levels of activity: 21°C
  • Special needs schools or areas with very young children: 21°C

Frost protection

'Frost Protection' is a feature built into most school boiler controllers which turns the heating on when it is cold outside in order to prevent frost damage to hot and cold water pipework.

A well-programmed control will turn the boiler on if a number of conditions are met, typically:

  • The outside temperature is below 4°C (the point at which water starts to freeze and expand)
  • And, the internal temperature is below 8°C
  • And, for some controllers if the temperature of the water in the central heating system is below 2°C

Typically, this means the 'frost protection' only turns the heating on if it is cold outside, AND the heating has been off for at least 24 hours - as it normally takes this long for a school to cool down and the internal temperature of the school to drop below 8°C. So, in general, in very cold weather the heating would probably not come on on a Saturday, but on a Sunday when the school has cooled down sufficiently.

Although 'frost protection' uses energy and therefore it costs money to run, it is cheaper than the damage which might be caused by burst pipes. Some schools don't have frost protection configured for their boilers and it is common for these schools to leave their heating on during winter holidays, which is significantly more expensive than if frost protection is allowed to provide the protection automatically. If your school heating system does not have a 'frost protection' option, set the heating thermostat to 8°C during the winter school holidays to minimise energy waste.

Common causes of central heating coming on too early in the morning

Many schools have ‘optimum start control’ configured which looks at the outside and inside temperatures and automatically schedules the heating to start earlier in colder weather and later in milder weather. Unfortunately, this does not work properly at most schools and is the cause of the heating coming on before 4am. This can be caused by:

  • Boiler thermostats being positioned in hard-to-heat areas of the school, such as the school hall or corridors. As a result, the corridors or hall might come up to temperature by the time the school opens but the classrooms have wastefully been up to temperature since the middle of the night! We generally recommend, if this is the case, to turn ‘optimum start control’ off and try switching to fixed times e.g. 6:30 am to 3:30 pm and see how it goes. 
  • Incorrect time settings. The time you set in the boiler controller is the ‘Occupancy time’ and not when you want the boiler to turn on. So, you should typically set it to 8:15 am, on the basis that you want the school up to temperature for 8:15 am and not, for example, 5:30 am in the mistaken belief that this is when the boiler will come on. If you set it to 5:30 am, all that will happen is that the ‘optimum start control’ will start the boiler earlier to get the school up to temperature for 5:30 am

What you should do

  • Set your heating to come on later in the morning and switch off about half an hour before school closes. Experiment with timings to see what time works best and saves the most.
  • If you have optimum start time settings on your boiler, check the time set is for ‘Occupancy time’ rather than the time you want the boiler to switch on. 
  • Experiment with moving the boiler thermostat to another area of the school or set the thermostat to a lower temperature. 
  • If you are reliant on your boiler service engineers to configure these settings, you need to be quite forceful with them and make sure that they understand that incorrect settings are costing the school money. If they make any changes, you can then review your gas or storage heater data on Energy Sparks a few days later to check the heating is now coming on at the correct time.
  • Keep an eye on the weather forecast, particularly in the Spring, and try to remember to turn your heating off when it is warm outside. Energy Sparks automatically emails you if it is going to be warm in the following week - keep an eye on your weekly alert email.
  • Don’t forget to set your heating to go off over the weekends and holidays:
    • Generally the only justifiable reason for using gas when it is unoccupied is for frost protection, which should only come on when the outside temperature drops below about 4°C, when there is a risk of water pipes bursting. 
    • If the school is to be occupied during the holidays by a few members of staff only, it is better to provide those staff with electric fan heaters, rather than heating the whole school, or if the school’s heating is zoned just leave the occupied zone on.
    • Hot water systems can be turned off to save energy during the holidays and weekends. After longer holidays, please remember to flush the system before the school is occupied again to reduce Legionella risk – you need to do this whether or not you have turned the heating off over a holiday.
    • You do not need to run hot water 24 hours a day, 7 days a week for legionella protection. You can switch off systems overnight and at weekends and should switch them on again in time to heat the water sufficiently before use. For more information on managing legionella risk, read the Health and Safety Executive (HSE) guidance Legionnaires’ disease: hot and cold water systems.