Thermostats and Programmers
A thermostat sets the desired room temperature whilst a programmer gives the user great control of the times the heating is on. A programmable room thermostat is a combined unit that does both. There are two main types of programmer: 1 day and 7 day (although some with a 5/2 day options). Most programmers will allow you set 2-6 time periods per day and also set different temperatures for each time period. If you only have a thermostat then your boiler will fire on and off all day unless 1) you turn the thermostat down when you out or 2) you switch the boiler off when you go out.
Single Channel and Twin Channel Programmers
A ‘channel’, like a radio channel, is the means by which the thermostat communicates with the systems it controls.
A programmable room stat will have commonly have one (single) or two (twin) channels, although some have three. The first channel will control the boiler. The second channel will control the hot water.
Single channel programmers
These are used with combi boilers, as it is not necessary to control the hot water separately (this is done by the boiler).
Twin channel programmers
These are used with regular and system boilers where the programmer needs to control the heating and the hot water timing. (They can also be used with combi boilers where there are two separate heating circuits or a mix of radiators and underfloor heating).
Three channel programmers
hese work with regular and system boilers to control two separate heating circuits plus the hot water. These are only used in larger properties where the ground and first floors are separately piped to create two radiator circuits (called zones) or where there is a mix of radiators and underfloor heating.
Load and Weather Compensation
‘Compensation’ controls are a form of advanced control that operate the boiler more efficiently.
Load compensation takes the difference between the lower internal room temperature and the desired room temperature and adjusts the boiler’s output to close the gap as efficiently as possible.
Weather compensation works in the same way but uses the external temperature. This traditionally involved a temperature sensor on the outside of a property linked to the internal programmer/thermostat. The sensor is able to forewarn the boiler of a change in outside air temperature which will eventually lead to a decrease or increase of inside temperature.
Some weather compensation systems use data from the local weather station to inform your heating system of a change in temperature. This is less accurate but makes for a more straightforward installation with fewer parts to go wrong.
For both weather and load compensation controls, the boiler can respond by increasing or reducing its output slowly to meet the predicted change in temperature. This leads to less ‘cycling’ (the boiler coming on and off) and more efficient periods of operation. NB for a control of this type to work it must speak the same ‘language’ as the boiler - for more go to our Guide to Advanced Heating Controls or try our Guide to Opentherm products and compatibility.
Smart controls with automation and optimisation functions
Smart controls (NB this is not necessarily an internet control) for the purposes of Boiler Plus automate the time and temperature settings based on occupancy detection, geolocation and/or stored data from user patterns over time. Smart controls work on a learned schedule of use and how quickly your home loses or gains heat. Over time the control will know how early the boiler will need to come on to meet the set temperature operating in its most efficient condensing mode. Smart controls of this kind work with all boilers. For more go to our Guide to Advanced Heating Controls.
All modern boilers are ‘modulating’. This means that they can adjust their output up and down. For example, an 18kW rated boiler can adjust its output to fire between 3kW and 18kW. Why is this important in a section on heating controls? Well in order for a modulating boiler to modulate, and thereby achieve its maximum efficiency, it must 1) work with a compatible ‘modulating’ heating control and 2) spend as much time as possible in ‘condensing’ mode, which can be achieved with the right heating control. For a boiler to modulate it needs to work with a compensation control that can speak the same language as the boiler. For more go to our Guide to Advanced Heating Controls or try our Guide to Opentherm products and compatibility.
Smart – internet - heating controls
Smart heating controls are all programmable thermostats that are connected to the internet and operable via a smart phone app. Most use some form of advanced heating control (i.e. weather compensation, load compensation and/or automation/optimisation features). Many are now compatible with Alexa, Apple, IFTTT and other smart home devices. This can provide additional functionality, for example you can turn your heating on and off via the voice activated smart home device or active geofencing sensors (the heating will come on as you near home via a GPS signal from your phone). NB some smart controls such as Nest and Tado come with geofencing as part of the device. For more on smart controls try our Guide to Smart Heating Controls or Guide to Home Automation Systems.