How to choose a multi-zone system

Picture of a Honeywell controller and a smart TRV
Honeywell evohome multi-zone

Multi-zone heating control is the best smart heating you can choose for you home. You don’t need to make any plumbing changes to your boiler or central heating system and end up with a heating system that can be controlled room by room.

What is multi-zone heating?

A typical UK home has a single thermostat that sets a target temperature for the whole house. It’s usually positioned somewhere that you never live in, like the hall. When your hall gets to the target temperature your boiler is switched off. No matter how cold you are in the living room and how much you turn the radiators up, the boiler won’t kick-in again until the thermostat target increases or the hall drops in temperature.

Hand altering a traditional (analogue) central heating thermostat
A single thermostat for the whole home is not energy efficient

The downside of this system is that it wastes a lot of energy and you often end up heating parts of the house you don’t need to or turning the thermostat up in order to get just one room warm enough.

Newer homes have 2 or more thermostats, maybe one for upstairs and one for downstairs. If you have 2 or more thermostats already – it’s because you have separate plumbed in heating circuits which means that one can be on while the other is off.

Multi-zone smart heating controls like the Honeywell Evohome system makes each zone independent by giving it a smart thermostat that controls the boiler. Each radiator valve is upgraded to a smart themostatic valve that will tell the boiler to fire up when that room needs it. By the boiler a wireless relay box replaced any manual controls you have and the whole system if controlled by an intelligent controller hub which can sit anywhere in your house.

Now, f you want to have the living room at 23C and study at 19C, you can. (see diagram below) And most importantly without effecting other zones/rooms in the house.

Illustration of temperature control for different rooms using Honeywell evohome multi-zone smart heating (c) homesm.art 2019, 2020
Honeywell Evohome enables you to set temperature room by room
Image of Honeywell evohome controller showing touch screen control of individual room temperatures - (c) homesm.art 2019, 2020
evohome controller

How does the evohome system work?

Basic Components of Honeywell Evohome

Controller Hub – (see pic above) This is the brains of your system.

Smart radiators valves – control the temperature of your room/zones.

Relays – wired to you boiler/hot water /under floor heating to control when they turn on or off.

Smart App – phone app to control your heating remotely

Zones or Rooms

You can effectively have as many zones as you want with Evohome.

There is no limit to the number of radiators that you can have in a zone but if it gets too big we might need to look at your set-up again.

The Honeywell Evohome controller supports up to 12 zones. That means you can normally create a zone per room but sometimes you may need to group 2 rooms together to create a zone. If your house is larger than this we simply add another Evohome controller etc.

Smart Radiator Valve

What is a smart radiator valve?

A smart radiator valve is a radiator valve that can be controlled wirelessly. It allows a smart heating system to control the radiator remotely, turning it on or off as required. This means that rooms or zones can be heated separately for cost efficient heating. Smart radiator valves are also known as smart thermostatic radiator valves or smart TRVsHoneywell HR92

Each radiator can be upgraded to a new smart thermostatic radiator valve. (see pic above). There is a battery powered motor and thermostat in each valve. When the valve gets a wireless signal to heat a room it opens the valve until the correct temperature is reached.  It then closes automatically and sends a signal back to the the controller.

If you have 2 or more radiators in a zone they will both need to be upgraded. One will become the master and they will be linked to work in unison.

Often radiators are “boxed in” behind radiator covers. In this case you still need to upgrade your valves but you will also need a separate wall thermostat to gauge the room temperature rather than the box temperature!

One important point is that your radiator valves need to be the TRV type not manual. If not, they can be upgraded quite simply. If you are unsure, I explain that a bit further down this article.

Evohome Controller

The Evohome controller is a wireless hub that you can plug in anywhere and is the brains of your system. With it you can set the required temperature for each zone. It does many clever things, but the most important are telling the boiler to start, telling the valves to turn on and off, showing you the temperature and managing your heating schedules.

It connects to your internet via wi-fi but it connects to all the Honeywell components via its own wireless system. So, if your internet goes down your heating keeps working!

If your home wi-fi is bit dodgy (technical term for a weak signal!) it doesn’t matter because Evohome operates on its own frequency of 866mhz. This is better for longer distances and also has less interference than your home wi-fi.

Honeywell Home app showing room temperatures controlled by evohome multi-zone smart heating
Control from the Honeywell app

You can also control your heating from the very smart Honeywell Total Connect app on your mobile phone (pictured above) or a smart speaker such as Amazon Alexa or Google Home.

Other communications devices

Evohome includes install smart ”relays” connected to your boiler. The relays send and receive signals from your evohome controller to the boiler but are hard wired to your boiler.

If you have a hot water tank we also wire in another relay and thermostat to that. If your water gets cold it triggers a signal to the evohome controller and boiler relay that it needs heat. With this system you can choose the temperature of your hot water and obviously the times it should be on.

Should I include all radiators?

Many people do not add every radiator to their multi zone system. The main reasons being cost or that is simply unnecessary.

What happens if you leave a radiator off your multi-zone system?

Any radiator left with traditional manual or TRV valves will still work. However, what does change is control. Because you no longer have a central thermostat the boiler is now triggered by the individual commands from your zones or hot water. Every time the boiler is triggered it will provide heat to your system. Any radiators with traditional valves left open will heat up. Of course, you can manually turn these off just as you today.

Should I leave rooms out from a multi-zone system?

This can make good sense for rooms that you either want heated most of the time (bathrooms) or not heated most of the time (spare room in the attic maybe?).

The most common is a bathroom or utility. Many people have 2 or even 3 types of heating in their bathrooms. For instance, radiator, heated towel rail and electric UFH. It doesn’t make much sense to automate a radiator when its not really controlling the room temperature.

Another big factor in bathrooms is that showers and baths create a lot of heat and tend to confuse thermostats. That’s why many bathrooms just have manual valves which is fine.

The same can be true for little used rooms. Keeping a traditional valve there may be a choice as you generally have it turned off. The thing to bear in mind is when you do need to use the room, heat will only be provided when the boiler is on.

What type of valves have you got?

Typical TRV Valve
Close Up Of Hand Adjusting Heating Thermostat

You need TRV valves to fit smart thermostatic valves. We simply unscrew them and put on the automatic smart ones. Then connect up wirelessly to the system.

If you have manual valves you need to change the physical valve to a TRV type. You can tell them apart by the TRV having numbers while the manual do not. The difference is that TRV valves work by pushing down a plunger valve to vary the flow of hot water whereas a manual valve turns a screw tap on and off.

Manual Radiator Valve
Typical Manual Valve

Replacing a manual valve is straightforward but not one a plumber likes doing as they generally have to drain the heating system first. This takes a long time and becomes an expensive job for such a small item.

If you’re going to do this please consider our service which we can do while we’re installing your multi-zone system which helps keep the costs down.

Multi-zone heating systems from homesmart

Homesmart Solutions provides multi-zone heating systems from Honeywell Evohome. As well as installation, we also provide service and support with our unique service plans.

Find out more on our multi-zone heating page

Installation of multi-zone heating

You can find out what to expect in having a multi-zone heating installed by Homesmart Solutions please read here.