Honeywell Evohome

At its most basic, Evohome is just like Nest. If you want to, you can buy a single zone connected thermostat pack (Y87RF2024/ RFG100 ) for under £140, install it yourself and it will work almost exactly as Nest and Netatmo’s (page 70) thermostats do.

This isn’t Evohome, though. It’s merely one of the components used in an Evohome system. It comprises a T87RF wireless room thermostat, a BDR91 wireless relay and an RFG100 ‘mobile access kit’ which connect to your router and makes the system controllable via the internet and Honeywell’s Total Connect Comfort app.

Such systems measure the temperature at one location (typically in the hall, just like your old thermostat) and heat the whole house until the thermostat reaches the set temperature, called the set point in heating jargon.

To avoid any one room becoming too hot, these systems rely on you already having thermostatic radiator valves (TRVs) installed. These shut off the radiator when the desired room temperature is reached, although you only have a dial that runs from 1 to 5, so you have to figure out which setting is best by trial and error. Your radiators may not have TRVs, of course. They could have a simple knob that you set manually to fully open, fully closed or somewhere in between.

Where smart heating systems really get smart is when you replace these knobs or TRVs with smart TRVs. Like ‘dumb’ TRVs they have built-in thermostats but can be controlled remotely. This is a huge advantage as it means you can have control over the temperature of each room without having to walk around your home turning individual radiators up or down manually.

The bad news is that smart TRVs are expensive. If you have 10 radiators you want to control, that’s £500 before you’ve added the cost of the controller, relay and installation.

This is why it makes sense to only control those radiators in rooms you spend the most time in. TRVs can also be grouped into ‘zones’, so you could have an upstairs zone and downstairs zone, and set each to different temperatures at different times of day. You might want to group all bedrooms as a zone, for example, and set it so they’re only heated first thing in the morning and just before everyone goes to bed.

While such a setup can save money in the long run, it takes a big initial investment.

Test system

We had an Evohome system installed into a large house in order to test out its full capabilities, controlling both radiators and underfloor heating (UFH). Honeywell has a system builder tool that helps you work out which components you need for your home. You tell it how many rooms you want to control, the type of heating in those rooms and whether you have a combi boiler, water tank or other heat source.

In our test home, the system builder advised three room thermostats, 10 smart TRVs, a UFH controller, hot water kit, mobile access kit and a base pack (the touchscreen controller).

The UFH controller can handle five zones, but is upgradeable to support eight zones if necessary. To save money, you can group UFH actuators into one zone: you don’t need to have each one on a separate zone. The UFH controller works with the T87RF wireless room thermostats to maintain a constant temperature in those rooms or zones.

Such a system needs professional installation, which took a full day. Not all our radiators had compatible valves for the TRVs, so some had to be changed over using pipe-freezing packs. The existing UFH controller had to be swapped out for the Honeywell one, and the sensor and relays installed for the boiler and hot water tank.

Despite thick stone walls and long distances from the Evohome controller to the furthest TRVs, there were no wireless connectivity problems. We did have to move the RFG100 as the controller couldn’t connect to it where we originally placed it next to the broadband router. However, using a pair of existing powerline adaptors we were able to relocate it to a more central position in the house.

How it works

The Evohome controller does the bulk of the work and lets you program a schedule as well as adjusting zone temperatures whenever you want to make a change. It can also act as a room thermostat on its own. The controller can be wall mounted, but since it requires mains power most people will prefer to leave it on its tabletop stand.

There’s an internal battery so you can slide it off its stand and use it completely wirelessly, but it’s more convenient to use the iOS or Android app. Unfortunately there are only unofficial apps for Windows Phone and BlackBerry, which lack the full set of features.

Using the controller or app, you can create zones by grouping TRVs and thermostats. This allows you complete freedom to set up the system as you like. The controller