Honeywell evohome ‘Smart’ Central Heating Control System
The evohome system allows you to divide a building up into up to 12 separate ‘Zones’.
Each zone would have at least one controller, but zones with multiple radiators would invariably have one controller per radiator, with one designated as the master controller for that zone.
Each zone (controller) can then be set to change temperature (over the full comfort range) at up to 6 distinct switching points per day (summer settings are shown here, hence most of the switching points have the same ‘arbitrary’ temperature):
Note: The evohome system is designed in such a way that the entire central heating system is configured as being ‘always on’, with the Zone Controllers (Radiator Controllers, Single Zone, Underfloor Heating Controllers etc.) switching the heating on and off for individual zones as required.
For this reason, it is essential that every radiator in the system has either an evohome Radiator Controller (optimal), or at the very least a traditional TRV (thermostatic radiator valve) fitted. The householder may decide to keep using TRVs on some radiators whilst gradually upgrading an existing system, or if an evohome Radiator Controller would simply not fit in the space available (they are a little larger), or if their white finish would not be appropriate (on a chrome radiator, for example).
If a TRV is used, the radiator it controls will heat up to the level set on the TRV whenever any evohome Controller in the building is demanding heat, so limiting the amount of control possible in this area.
Once the zones have been set-
Once all the Radiator Controllers, wall-
Once all the zones have been set up, then the ‘switching points’ (times at which a change in temperature is required) need to be set-
As should by now be clear, this does mean that programming an evohome system does involve a lot more time / effort than for a normal single zone system. However, the use of a ‘Copy and Paste’ function between both days of the week and zones can make this significantly easier / quicker than it may first appear.
Once all the zones have been programmed, it should only be necessary to make minor adjustments to the programming to ‘tweak’ the desired temperatures etc.
The controller (and associated ‘App’) also allows the use of simple ‘Quick Action’ commands to set the whole system up. ‘Away’, for example, lowers the temperature of all zone settings and switches the Hot Water off and ‘Day Off’ sets the temperatures / timings as if for a weekend (see the ‘App’ section for more information).
A number of more advanced settings are also available in the ‘Advanced’ menu, accessed by holding down the ‘Settings’ icon for a few seconds. Many of these settings are designed more for the installer than the homeowner and should only be changed if fully understood (for example, setting the maximum Hot Water temperature, type of boiler / motorised valve).
Once the initial programming has been set-