Five-minute Guide to… Heating Controls
The technology for controlling the heating in our homes is advancing rapidly, says energy efficiency expert Tim Pullen
109 The technology for controlling central heating in our homes is advancing rapidly. Energy-efficiency expert Tim Pullen explains what’s new and the potential cost savings to be made
For had fairly as heating long crude, as controls. essentially we have had Admittedly dealing central with heating these the used tempera- we to have be ture of the whole house from a single thermostat. The last few years has seen a rapid development in control technology, which can make a significant difference to accuracy, efficiency and, ultimately, to the heating bill. And as is so often the case, there is now a plethora of choice and it is difficult to know what is best.
Setting the Parameters
A combi boiler, much loved by the property developer, will use just a single timer or programmer, as water is heated as required. There are serious question marks over whether this is a good idea for the homeowner as it offers the bare minimum level of control.
Similarly, a simple indirect hot water cylinder will have a thermostat fixed to the cylinder to measure the temperature implication all will the be of water at the the water of in same this the in cylinder temper- is it. that The ature to heat and it the until boiler the will desired run temperature is reached. A thermal store offers far more control as it will store water at a range of temperatures. If we have underfloor heating we want water at around 40°C but we also want domestic hot water at 64°C to kill legionella bacteria. The controls inherent in a thermal store allow us to do that without wasting energy.
The Fall of TRVS
The old-style analogue room thermostat is still being installed, usually one to each floor. At best, these are accurate to +/-2°C — poorer quality ones can double that inaccuracy. Together with a programmer that allows the heating to be switched on and off multiple times each day, and to deal with hot water separately, this is a better option than
“The last few years have seen a rapid development in control technology”
“Estimates on the savings that zone control can give vary — some put it as high as 20%”
a combi boiler, but by not much. More common now are thermostatic radiator valves (TRVS). These are, as the name suggests, fitted to the radiator, with graduation typically from one to six. They give no indication of the actual temperature in the room, beyond comfortable or uncomfortable. These were de rigueur for a few years but have, thankfully, fallen out of favour.
The big change in the past few years has been the realisation that different rooms need different temperatures at different times, often referred to as zone control.
The Rise of Zone Control
Zone control actually means controlling the heating in each room, and it can be done in one of two ways: centrally or individually.
An underfloor heating system will be controlled centrally, with a thermostat in each room reporting back to the central programmer where the homeowner sets the time and temperature for each room.
For radiator systems a similar level of control comes via programmable radiator thermostats. These are battery powered and allow for precise control of the time and temperature in each room. They are fitted like TRVS and some simply replace the body of a pre-existing TRV so that the heating system does not have to be drained down. There are also wireless options that can be programmed from a central point, otherwise each thermostat has to be programmed individually.
Remote Heating Controls
The emergence of remote heating controls has been gaining a lot of press coverage in the last couple of years. A phone app allows the user to change the temperature or timing of the heating and/or hot water system from wherever they happen to be.
The one we have all heard of is the Hive Active Heating control, marketed by British Gas, but there are many others: Heatmiser, Tado, Nest, to name a few. Some, like the Nest and Tado, are said to be intelligent in that they learn the user’s habits and automatically change their settings to meet prevailing conditions — they can apparently detect that the homeowner is not in the house and will delay switching the heating on, or turn it off.
These systems have a device in the house that connects to the existing control system, which is accessed via a phone app. The thinking is that if the user has a ‘ busy’ lifestyle (that is, a propensity to go somewhere other than home after work) then the app will allow them to adjust the heating accordingly. There are significant claims made there trolling are for the these applications heating devices, in where a like holiday ‘savings this home. could of £150 So be far true, per the year’ like Energy con- and Saving Trust has been unable to confirm how accurate those claims are. The Hive device has so far proved the most popular with more than 100,000 units sold. This sounds like a lot, but there are around 22 million homes in the UK so there is still a large market to work on.
British Gas recently conducted a survey of 2,000 users and more than 70% said they had saved money after having the gadget installed. To put it another way, up to 30% (or 30,000 people from the total 100,000 units sold) may have wasted their money.
Cost and Potential Savings
The cost of a zone control system for an underfloor heating system will, of course, vary with the size of the house and the manufacturer. Budget £1,000 to £2,000 for an installed system. Programmable radiator thermostats will cost £20 to £30 each, plus installation. The wireless option will add £200 to £300 to the bill. The remote control system will cost from zero (the Nest device is free to Npower customers) to around £300, including installation. The Hive device is £199.
Estimates on the savings that zone control can give vary — some put it as high as 20%. When you think that a bedroom will probably only need heating for one to two hours per day, while the living room and kitchen may need heating for eight hours or more, you can see where those estimates come from.
Being in control of your heating system is a good thing, and more control is undoubtedly a better thing. Well-insulated homes allow the system to bring the house to the desired temperature, within less than 1°C, and keep it there. Controls also allow rooms not currently being used to be treated differently. But bear in mind that whichever control system you use, it needs the home to be well-insulated to be really effective.