TechReport (UK)

Product Reviews:

Honeywell evohome ‘Smart’ Central Heating Control System


Warning:   Although most components in the evohome system can be installed by any keen DIY enthusiast, this is certainly not the case for the mains powered components, which are designed to directly control critical central heating elements such as the boiler or powered valves – these should only be installed by suitably qualified personnel (typically those with a ‘Gas Safe’ certificate). This would include Wireless Relay Boxes, Mixing Valve Controllers, Underfloor Heating Controllers and OpenTherm Bridges.

The most basic version of an evohome system can be had by purchasing a ‘Starter Kit’ (~£200) consisting of the  evohome Controller and a Wireless Relay Box.

Once the Wireless Relay Box has been correctly wired to control the boiler or motorised valve by a competent professional and the controller has been suitably programmed (see Programming the System), this gives the user the same degree of control as a standard room thermostat / central heating programmer combination, with the building represented as a single zone.

In addition, by using the FOC App (Apple and Android stores), you can change all settings remotely from anywhere in the world with a mobile phone or WiFi signal.

Although this could be a good starting point for setting up an evohome system, it does rather miss the main point – although the control flexibility increases, only limited efficiencies can be achieved with this configuration as the entire building is still being treated as one unit.

To really utilise the system to the max, most will also purchase a number of the Radiator Controllers (available for just under £50 each if several are purchased at once).

This is where the evohome system really comes into its own.  If you currently have a traditional central heating system with just one room thermostat (typically situated in the main living area) and a separate programmer, you may well already have questioned why it should be necessary to heat the whole house up to the same temperature in order to be comfortable in just the room you are occupying.

Yes, you can use thermostatic valves to give some degree of localised control, but you would have no way of telling a valve that you want a bedroom to be warm early in the morning and late in the evening, but not to waste energy heating it when you are downstairs, for example.

In order to fully benefit from the evohome system functionality, it is now necessary to break the control of the central heating system down further using a concept known as zoning.

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