Helpful video reference. We use this UK installation tutorial as the video reference for this guide. It covers the relay box wiring and app pairing steps that matter for UK boiler setups.
1. Check compatibility
The Netatmo Smart Thermostat works with most UK gas combi and system boilers, as well as oil boilers and heat pumps with a standard on/off switching input. Check the Netatmo compatibility list before you buy. You will need your boiler make and model.
The standard Netatmo thermostat (NTH01) uses simple on/off control: it switches the boiler on and off based on the room temperature. If your boiler supports OpenTherm modulation and you want load-compensating control, Netatmo also makes an OpenTherm-compatible modulating thermostat (the OTH-PRO), which works differently and needs a different wiring approach.
This guide covers the standard NTH01 on/off version, which is the most common choice for UK homes.
2. Understand the relay and thermostat
The Netatmo system has two parts:
- Relay box (the boiler switch unit): mounts near the boiler or in the airing cupboard. It connects to the mains supply and to the boiler switching terminals. It also connects to your home WiFi so you can control heating remotely via the app.
- Thermostat unit (the round chrome unit): battery-powered, no wiring needed. Place it on an internal wall in the room you want to control. It pairs wirelessly with the relay.
The relay box replaces the old wired programmer. The thermostat unit replaces the old room thermostat.
3. Isolate the boiler supply
Switch off the boiler at its fused spur or at the Heating MCB in the consumer unit. Switch off the programmer too if it is on a separate circuit.
Test with a voltage tester at the programmer terminals and at the existing thermostat location. Dead on everything before you remove a single wire.
Take clear photos of the programmer wiring and any wiring centre. You will refer to these photos when connecting the relay box.
4. Wire the relay box
The relay box has five key terminals:
- L, N, E - mains supply terminals. Connect the L, N and E conductors from the existing programmer supply.
- NO and COM - the boiler switching terminals. Connect these to the same pair of terminals that the old programmer's switching output used to control the boiler (or to the wired room thermostat terminals if you had a wired thermostat rather than a programmer).
On a combi boiler, the NO and COM terminals typically go to two terminals on the boiler labelled TA (thermostat input) or similar. On a system or regular boiler with a separate wiring centre, they go to the heating call-for-heat terminals. The existing programmer's wiring diagram or the boiler manual will identify the correct pair.
Mount the relay box on the wall using the included bracket. Restore power briefly to confirm the WiFi LED is active on the relay, then isolate again.
5. Place the thermostat unit
Choose a position on an internal wall about 1.5 m from the floor, away from radiators, direct sunlight and draughts. The thermostat reads room temperature, so placement matters.
The thermostat unit is battery-powered (two AA batteries, typically lasting 12 to 18 months). It communicates wirelessly with the relay box via your home WiFi. No wiring required at the thermostat location.
If you want a permanent mount, the thermostat clips onto a small bracket that screws to the wall. Otherwise it can sit freely on a shelf.
6. Commission via the Netatmo app
Download the Netatmo Energy app (iOS or Android) and create a Netatmo account. The setup sequence is:
- Restore power to the relay box. Its WiFi LED should flash.
- Add the relay box in the app by scanning the QR code on its underside or entering the serial number.
- Connect the relay to your home WiFi when the app prompts.
- Add the thermostat unit by pressing the button on its front when prompted.
- Enter your boiler type, home name and postcode.
The Netatmo app gives you remote control, a weekly schedule, and energy-saving suggestions based on your heating patterns.
7. Set a schedule and test
In the app, raise the target temperature above the current room reading. The relay should click on within a few seconds and you should hear the boiler fire. Check the app confirms the system is heating.
Create a weekly schedule. Netatmo's auto-adapting feature watches how long your home takes to reach the target temperature and adjusts the start times automatically over the first few days, so you do not need to allow for warm-up time manually.
If you have a system boiler, check that hot water control is still working correctly. The Netatmo standard thermostat controls heating only. Hot water on a system boiler is normally handled by a separate timer, which the Netatmo does not replace.
When to call us
A combi boiler install is the simplest case and most homeowners handle it without help. If you have a system boiler with a wiring centre in the airing cupboard and separate zone valves for heating and hot water, call Richard first. The Netatmo can still work, but the wiring is a little more complex and it is easy to leave the hot water on an unintended circuit.
Need a Netatmo thermostat fitted in east Kent?
Richard installs smart thermostats and heating controls across Sandwich, Deal, Dover and the surrounding area.
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