Now that we’re clear what a combi boiler is, some combi boiler systems have two separate heating zones, controlled by two thermostats. CHARACTERISTICS OF COMBI BOILERS (two heating zones)

HubR: User: Push Button/LED; I/O: Mains Relays (1-3), Digital Boiler Interface; Room thermostat: User: TFT display, touch buttons; I/O: None; Radiator thermostat: User: Twist Cap, LED; I/O: None Combi boilers only allow for one hot tap, bath or shower to be running at a time, by running more than one it will significantly reduce the pressure to each, which can be a problem for larger households with high demand for hot water. A system that was originally fully gravity-fed that has been upgraded/retrofitted with motorised valves, such that the central heating is now fully pumped - a recommended upgrade if full replacement of an older gravity-fed system is not possible.That’s clever, as you can have a spare room that’s set to keep it just warmed (to prevent condensation) using one schedule; when a guest comes, you can apply a different schedule. It’s slightly more work to do that here than with custom modes on Honeywell Evohome, but I still appreciate the flexibility on offer. Consists of a central heating boiler and a separate, pressurised hot water tank fed directly by the cold water mains feed, so the tank heats and stores hot water at mains pressure. These smart radiator thermostats replace the TRVs (thermostatic radiator valves) on your radiator, the type that let you adjust the temperature of the radiator manually. If you don’t have TRVs then you’ll need to bear the cost of changing your current valves to TRVs on top of the cost of the smart heating system. There’s no denying the radiator thermostats are bulkier than TRVs, but we found we didn’t notice them as much as we expected to. The Heat Hub is a rectangular box with two buttons. One button activates the set-up process, while the other starts the whole system heating. LEDs above the buttons glow green when these options are active. The Heat Hub should be screwed to the wall next to your boiler. The square smart thermostat has a two-inch screen that shows the current temperature of the room it’s in, as well as the desired temperature. It also displays the relative humidity and battery level, and features a flame icon to indicate if the heating is switched on. Honeywell Evohome gives more flexibility, with its custom actions and IFTTT channel. Its radiator thermostats are also more fully featured, letting you set the temperature you want from the room. If you want the most powerful and flexible multiroom heating system, then, we’d recommend Evohome.

With the standard kit, you get two TRVs and one room thermostat. If you start with this, you can put the TRVs into your most heavily used rooms for individual control, and the room thermostat elsewhere in the house to control everything else. Wiser thermostat and multi-zone kits 2 and 3 may be compatible with gravity-fed systems that have been retro-fitted or upgraded with pumps and cylinder thermostats - Please speak to our Technical Support Helpline on 0333 6000 622 for further advice on your system’s compatibility. Requires a three-channel Wiser kit ( Wiser Thermostat Kit 3) – note that you won’t require the third channel, because the hot water control in a combi system is not separate. A two-channel kit is not suitable for a combi system with two heating zones as the second channel in the two-channel kits is only suitable for hot water control in a conventional boiler system (with a separate hot water tank). You can tap on a room and edit the schedule or access the room settings, where you can view the battery level for the thermostat, rename it and turn Open Window Detection on or off. Editing a schedule was made super-easy as a result of the ‘copy’ feature, which lets you duplicate a schedule with just one tap, rather than having to input it all for each day and on each device.Comfort Mode is there to make sure that your home hits the target temperature at the set point rather than turning the heating on at that point. In other words, if you get up at 7:30am and set a schedule to have your heating at 18°C at this time, your house will be warm when you wake up. Away Mode overrides your existing schedules with a lower set temperature of your choosing, ensuring your home doesn’t get too cold while you’re away. You can turn off appliances in Away Mode, too. You can also set up geofencing using IFTTT so your system will automatically switch to Away Mode when you’re out of the house. Hot water is available on demand independently of the central heating, without having to wait for a water cylinder to heat up. In addition, each room can have Open Window Detection turned on. This uses an algorithm to detect when a draft is detected, suggesting an open window or door. The heating is then turned off to conserve energy. That’s neat, as you can start with the cheap kit and then upgrade as you see fit to add TRVs to every radiator in the house. Once you’ve done that, the room thermostat can be used to control a room and all TRVs in it, as Wiser supports rooms with multiple radiators.