Heating controls was the subject of half my Cosy Cambridge workshop on Monday. With the help of some friends we managed to cover all the basics and had a good discussion on whether 'smart' controls were a good idea, or rather under what circumstances you would benefit. You can download the slides from my website here.
You need controls for when, where and how much you heat, and to run the boiler efficiently.
The point of heating controls is two-fold. Firstly, controlling when, where and how much you heat your home (or other building) and secondly doing this in a way that allows your boiler to run efficiently. Gas boilers have their limitations. Frequent switching on and off is wasteful and for condensing boilers to condense properly the temperature of the water returning to the boiler needs to be no more than 55C. Modern boilers can run at partial load to reduce cycling - the technical term for this is 'modulation'. They can do this by themselves, by sensing the return temperature and adjusting the flame level to keep this within an optimal range. However it will take a little while for them to adapt when conditions change. If this is controlled by the thermostat they can respond more quickly.
Basic controls are timer, central thermostat and TRVs
Basic controls are just a programmer/timer, central thermostat and TRVs on the radiators. A programmer will allow you to set different temperatures at different times of the day. The boiler will come on whenever the you are in a heating period and the thermostat detects that the temperature is below the required level. The TRVs control heat through each radiator, but they don't turn interact with the central thermostat to turn the boiler on or off.
If you have regular habits and a small and/or very efficient home so that you want to heat either none of it or all of it at any one time then this is for you. Otherwise you might need some finer control. This can be manually configured, so you are in complete control, or it can be an 'intelligent' system by which I mean something that configures itself by learning or watching what you are doing.
Here are some of the features of smart heating controls that you might find helpful. Different systems have different functionality and some are not really intelligent, though anything that comes with a smart phone app will doubtless call itself smart.
Zoning
What is it? You divide the house into zones and each has its own heating circuit with thermostat and schedule. The boiler comes on if any zone needs heat. This allows you to have different schedules in different parts of the house. For example, you could heat the bedrooms first thing in the morning and in the late evening and the study during the day. Or if you have a lodger you could give them a zone for their room(s) so they can be independent of the rest of the heating.
Why would I want it? If your house is large enough that you don't use all of it all the time but different bits at different times. However, installing this might mean a lot of disruptive plumbing.
Am I in control? Yes.
Weather compensation
What is it? The boiler adjusts the temperature of water flowing to the radiators depending on the outside temperature. This keeps the return temperature below 55C at all times. If the boiler can do modulation as well this reduces cycling. See IsoEnergy for more detail.
Why would I want it? Possibly not. An intelligent boiler that modulates based on sensing the return temperature could do almost as well though it will take time to react.
Am I in control? With some systems you will have to configure it by selecting a heating curve. 'Smart' systems will work it out for themselves by learning how long it takes to heat your building.
Optimum start/delayed start
What is it? Rather than telling the timer when you want the heating on you tell it when you want to be warm. The system knows how long it takes to heat your house depending on the temperature outside.
Why would I want it? Most homes will benefit by not running the heating longer than necessary. Presumably you have set your heating schedule so that your house does normally come up to temperature when you want it to even in cold weather. Then when it is not quite so cold it comes up to heat earlier than necessary and you waste energy keeping it at that temperature. If it is a very well insulated house it may not need much heating to keep it up to temperature so this won't save you much.
Basic controls are timer, central thermostat and TRVs
Basic controls are just a programmer/timer, central thermostat and TRVs on the radiators. A programmer will allow you to set different temperatures at different times of the day. The boiler will come on whenever the you are in a heating period and the thermostat detects that the temperature is below the required level. The TRVs control heat through each radiator, but they don't turn interact with the central thermostat to turn the boiler on or off.
If you have regular habits and a small and/or very efficient home so that you want to heat either none of it or all of it at any one time then this is for you. Otherwise you might need some finer control. This can be manually configured, so you are in complete control, or it can be an 'intelligent' system by which I mean something that configures itself by learning or watching what you are doing.
Here are some of the features of smart heating controls that you might find helpful. Different systems have different functionality and some are not really intelligent, though anything that comes with a smart phone app will doubtless call itself smart.
Zoning
What is it? You divide the house into zones and each has its own heating circuit with thermostat and schedule. The boiler comes on if any zone needs heat. This allows you to have different schedules in different parts of the house. For example, you could heat the bedrooms first thing in the morning and in the late evening and the study during the day. Or if you have a lodger you could give them a zone for their room(s) so they can be independent of the rest of the heating.
Why would I want it? If your house is large enough that you don't use all of it all the time but different bits at different times. However, installing this might mean a lot of disruptive plumbing.
Am I in control? Yes.
Weather compensation
What is it? The boiler adjusts the temperature of water flowing to the radiators depending on the outside temperature. This keeps the return temperature below 55C at all times. If the boiler can do modulation as well this reduces cycling. See IsoEnergy for more detail.
Why would I want it? Possibly not. An intelligent boiler that modulates based on sensing the return temperature could do almost as well though it will take time to react.
Am I in control? With some systems you will have to configure it by selecting a heating curve. 'Smart' systems will work it out for themselves by learning how long it takes to heat your building.
Optimum start/delayed start
What is it? Rather than telling the timer when you want the heating on you tell it when you want to be warm. The system knows how long it takes to heat your house depending on the temperature outside.
Why would I want it? Most homes will benefit by not running the heating longer than necessary. Presumably you have set your heating schedule so that your house does normally come up to temperature when you want it to even in cold weather. Then when it is not quite so cold it comes up to heat earlier than necessary and you waste energy keeping it at that temperature. If it is a very well insulated house it may not need much heating to keep it up to temperature so this won't save you much.
Am I in control? Most systems will configure themselves by 'learning' how long it takes to heat up the house.
Holiday Mode
What is it? If you are going to be away for a few days you can tell the boiler when you are coming back. It will run the house at a low thermostat setting and not heat any hot water until you are about to return.
Why would I want it? If you are away a lot in winter you will save heating while you are away but still come back to a warm house. Even in summer you will save on hot water heating if you have a system boiler. But you can also do this by remote control (see below).
Am I in control? Yes
Instant temperature boost (heating or hot water)
What is it? You can temporarily override the heating schedule to make it heat the hot water tank now, or turn the thermostat up a bit for a short time.
Why would I want it? It can be useful if your hot water tank isn't big enough for an influx of guests, or if you sometimes want a quick warm up.
Am I in control? Yes
Remote control
What is it? Instead of having a programmer on the wall, you control your heating from a smart phone app. You still need a thermostat somewhere on the wall. Also it needs an internet gateway.
Why would I want it? If you have irregular habits and want to be able to turn the heating off and on manually, possibly while travelling, then this is the only way to do it. You might also prefer the phone app interface as it is more like what you are used to, rather than strange knobs and buttons. Of course you do need a smart phone.
Am I in control? Yes.
Motion sensing/presence sensing.
What is it? The system uses sensors around the house to see if you are home and where.
Why would I want it? If you have irregular habits and don't want to have to turn the system on and off manually. It can save energy by turning the heating off if you are not at home. If you have smart TRVs then the room sensor can communicate with them and turn down the heating in the rooms you are not using. It can also learn your habits.
Am I in control? No.
Geolocation
What is it? The system knows where you are based on the location of your smart phone. If there is more than one of you then you all have to carry a smart phone and run the app. When you are close to home the system gets ready so that it can make your house warm before you get home.
Why would I want it? If you have irregular habits and don't want to have to turn the system on and off manually. It can save energy by turning the heating off if you are not at home. But if you spend a lot of time out of the house but close by it could end up heating your house unnecessarily in case you go home.
Am I in control? No.
Smart TRVs
What is it? These TRVs talk wirelessly to the central thermostat so they can tell the system whether or not heat is needed. This avoids the problem where you are cold but the central thermostat is warm or vice versa: either you aren't getting heat when you want it or you are warming the house more than necessary. In most cases you can program a schedule into each TRV as well, so that effectively each room is its own zone. They can also communicate with presence sensors in each room.
Why would I want it? If you have a large/leaky house and the central thermostat is not a good guide to the temperature in other rooms, then this will help. Or if you want to install multiple zones without a lot of disruptive plumbing and wiring this is a way to do it. However, this will not necessarily be cheaper as the TRVs are expensive. Also they run on batteries which you will need to replace regularly.
Am I in control? Yes.
Table mounted wireless thermostats
What is it? This is a battery powered thermostat that communicates wirelessly with the rest of the system and you can carry it around with you from room to room wherever you are. (Not to be confused with wireless thermostats that are designed to mount on the wall and you can't carry them around with you).
Why would I want it? If there is only one of you, or you are usually together, then you can keep the thermostat with you and optimise the heating for where you are. If you are prepared to twiddle TRVs off and on as you move around then you can have very fine control of exactly where heat goes at all times.
Am I in control? Yes.
Learning thermostat
What is it? With these thermostats (such as Nest) you don't have to select a temperature or set a schedule. It learns from you, with presence sensing to tell it when you are at home and you telling it when you are too warm or too hot.
Why you would want it? If you find programming a thermostat difficult (which many people do).
Am I in control? No
Is it OK to rely on internet services?
Obviously if you have a phone app you need access to the internet to run your system. Also geolocation relies on mobile networks and the internet to tell the system where you are. For optimum start and weather compensation they need external temperature data which they can either get from a sensor you install or they will need to get weather forecasts from the internet. However even systems that could be self contained may use services that are based in the cloud to do the intelligent bit. Nest is one example.
We discussed if this was a security issue and came to the conclusion this was probably OK, as long as there is no way to link your location data with your address. You don't want people checking if you are home and burgling your house while you are away. Another potential problem was if you have a flaky internet connection. If you are temporarily offline what does that mean for your heating? And more disastrous though hopefully less likely, what if the company supplying the services goes bust? That could mean your heating system stops working altogether, at least until another provider takes on your contract. It might be risky to install a product that relies on a cloud based system from a small startup company. I have friends who lost a solar panel monitoring system that way, because the company serving the data went out of business. The panels still work but they have reverted to recording the generation meter readings manually.
Should I rent or buy?
Some companies allow you to rent the system rather than buy which substantially reduces up front cost. But you still need to pay to have it installed and if you decide to cancel the contract you have to pay to have it replaced and send it back.
Should you take care to avoid proprietary lock-in?
We have Vaillant controls at home which suit us very well for functionality but it locks us into that manufacturer. We can't change to another brand of heating system (or heat pump) without changing the controls and we can't switch controls on our current boiler without losing functionality. If you don't want to be locked in but you do want smarts, look for a boiler and controls that support OpenTherm, an open standard widely supported by 'smart' controllers that allows them to control a modulating boiler. See Modulating 'A' rated boilers (myboiler).
Will smart heating systems save you money?
Between us we had no good examples of smart controls reducing heating bills. Usually we had made other changes to our houses at the same time as the new heating system, and we very rarely had good data on consumption prior to the change, even if we had been monitoring carefully since. So it was impossible to tell what savings were due to the controls.
It seems logical that there must be savings but the extravagant claims from manufacturers tend to be relative to a system with very limited controls if any. You won't save much money if you are already reasonably in control of your heating. If you have a large house with different bits used at different times then zoning should help, or possibly a wireless thermostat. If you have a leaky house then delayed start would help, but insulating and draught proofing it would be even better. Also you probably won't make savings if you were cold to start with and now you are warm.
On the other hand, if you aren't in control because you are not confident in programming the thermostat you might want an easy to use system like Nest. If you have irregular habits but you like to be in control then remote control through a smart phone app is probably best for you. Or maybe you just like to have a smart app for your heating because it is convenient and cool to show to your friends.
 |
| This is a system without optimum start. The heating comes on 4am which is just early enough to bring the house to 20C by 7am if it is 0C outside. If it is warmer, then it comes up to temperature quicker and wastes energy keeping the house warm until 7am. |
Holiday Mode
What is it? If you are going to be away for a few days you can tell the boiler when you are coming back. It will run the house at a low thermostat setting and not heat any hot water until you are about to return.
Why would I want it? If you are away a lot in winter you will save heating while you are away but still come back to a warm house. Even in summer you will save on hot water heating if you have a system boiler. But you can also do this by remote control (see below).
Am I in control? Yes
Instant temperature boost (heating or hot water)
What is it? You can temporarily override the heating schedule to make it heat the hot water tank now, or turn the thermostat up a bit for a short time.
Why would I want it? It can be useful if your hot water tank isn't big enough for an influx of guests, or if you sometimes want a quick warm up.
Am I in control? Yes
Remote control
What is it? Instead of having a programmer on the wall, you control your heating from a smart phone app. You still need a thermostat somewhere on the wall. Also it needs an internet gateway.
Why would I want it? If you have irregular habits and want to be able to turn the heating off and on manually, possibly while travelling, then this is the only way to do it. You might also prefer the phone app interface as it is more like what you are used to, rather than strange knobs and buttons. Of course you do need a smart phone.
Am I in control? Yes.
Motion sensing/presence sensing.
What is it? The system uses sensors around the house to see if you are home and where.
Why would I want it? If you have irregular habits and don't want to have to turn the system on and off manually. It can save energy by turning the heating off if you are not at home. If you have smart TRVs then the room sensor can communicate with them and turn down the heating in the rooms you are not using. It can also learn your habits.
Am I in control? No.
Geolocation
What is it? The system knows where you are based on the location of your smart phone. If there is more than one of you then you all have to carry a smart phone and run the app. When you are close to home the system gets ready so that it can make your house warm before you get home.
Why would I want it? If you have irregular habits and don't want to have to turn the system on and off manually. It can save energy by turning the heating off if you are not at home. But if you spend a lot of time out of the house but close by it could end up heating your house unnecessarily in case you go home.
Am I in control? No.
Smart TRVs
What is it? These TRVs talk wirelessly to the central thermostat so they can tell the system whether or not heat is needed. This avoids the problem where you are cold but the central thermostat is warm or vice versa: either you aren't getting heat when you want it or you are warming the house more than necessary. In most cases you can program a schedule into each TRV as well, so that effectively each room is its own zone. They can also communicate with presence sensors in each room.
Why would I want it? If you have a large/leaky house and the central thermostat is not a good guide to the temperature in other rooms, then this will help. Or if you want to install multiple zones without a lot of disruptive plumbing and wiring this is a way to do it. However, this will not necessarily be cheaper as the TRVs are expensive. Also they run on batteries which you will need to replace regularly.
Am I in control? Yes.
Table mounted wireless thermostats
What is it? This is a battery powered thermostat that communicates wirelessly with the rest of the system and you can carry it around with you from room to room wherever you are. (Not to be confused with wireless thermostats that are designed to mount on the wall and you can't carry them around with you).
Why would I want it? If there is only one of you, or you are usually together, then you can keep the thermostat with you and optimise the heating for where you are. If you are prepared to twiddle TRVs off and on as you move around then you can have very fine control of exactly where heat goes at all times.
Am I in control? Yes.
Learning thermostat
What is it? With these thermostats (such as Nest) you don't have to select a temperature or set a schedule. It learns from you, with presence sensing to tell it when you are at home and you telling it when you are too warm or too hot.
Why you would want it? If you find programming a thermostat difficult (which many people do).
Am I in control? No
Is it OK to rely on internet services?
Obviously if you have a phone app you need access to the internet to run your system. Also geolocation relies on mobile networks and the internet to tell the system where you are. For optimum start and weather compensation they need external temperature data which they can either get from a sensor you install or they will need to get weather forecasts from the internet. However even systems that could be self contained may use services that are based in the cloud to do the intelligent bit. Nest is one example.
We discussed if this was a security issue and came to the conclusion this was probably OK, as long as there is no way to link your location data with your address. You don't want people checking if you are home and burgling your house while you are away. Another potential problem was if you have a flaky internet connection. If you are temporarily offline what does that mean for your heating? And more disastrous though hopefully less likely, what if the company supplying the services goes bust? That could mean your heating system stops working altogether, at least until another provider takes on your contract. It might be risky to install a product that relies on a cloud based system from a small startup company. I have friends who lost a solar panel monitoring system that way, because the company serving the data went out of business. The panels still work but they have reverted to recording the generation meter readings manually.
Should I rent or buy?
Some companies allow you to rent the system rather than buy which substantially reduces up front cost. But you still need to pay to have it installed and if you decide to cancel the contract you have to pay to have it replaced and send it back.
Should you take care to avoid proprietary lock-in?
We have Vaillant controls at home which suit us very well for functionality but it locks us into that manufacturer. We can't change to another brand of heating system (or heat pump) without changing the controls and we can't switch controls on our current boiler without losing functionality. If you don't want to be locked in but you do want smarts, look for a boiler and controls that support OpenTherm, an open standard widely supported by 'smart' controllers that allows them to control a modulating boiler. See Modulating 'A' rated boilers (myboiler).
Will smart heating systems save you money?
Between us we had no good examples of smart controls reducing heating bills. Usually we had made other changes to our houses at the same time as the new heating system, and we very rarely had good data on consumption prior to the change, even if we had been monitoring carefully since. So it was impossible to tell what savings were due to the controls.
It seems logical that there must be savings but the extravagant claims from manufacturers tend to be relative to a system with very limited controls if any. You won't save much money if you are already reasonably in control of your heating. If you have a large house with different bits used at different times then zoning should help, or possibly a wireless thermostat. If you have a leaky house then delayed start would help, but insulating and draught proofing it would be even better. Also you probably won't make savings if you were cold to start with and now you are warm.
On the other hand, if you aren't in control because you are not confident in programming the thermostat you might want an easy to use system like Nest. If you have irregular habits but you like to be in control then remote control through a smart phone app is probably best for you. Or maybe you just like to have a smart app for your heating because it is convenient and cool to show to your friends.
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