How to install a Wi-Fi room thermostat
Updated: October 2026
How to install a Wi-Fi room thermostat, in a UK house, starts with a fork rather than a drill. You already own a stat you believe matches the boiler, and you want the order of checks plus the point where you stop. A five-minute review is someone else's wiring. Confirm the interface, isolate the circuit, and put the tools down before you open a boiler case or invent a joint for an unlabelled core. The [Wi-Fi room thermostat comparison](/hub/thermostats/wifi-room-thermostat) is the product table, not a wiring diagram. Products Compared used public UK sources and notes on these listings. This is not a Gas Safe ruling and not a personal test. A qualifying purchase can earn a commission at no extra cost to you.
How to install a Wi-Fi room thermostat, in a UK house, starts with a fork rather than a drill. You already own a stat you believe matches the boiler, and you want the order of checks plus the point where you stop.
How to install a Wi-Fi room thermostat, in a UK house, starts with a fork rather than a drill. You already own a stat you believe matches the boiler, and you want the order of checks plus the point where you stop. A five-minute review is someone else's wiring. Confirm the interface, isolate the circuit, and put the tools down before you open a boiler case or invent a joint for an unlabelled core. The Wi-Fi room thermostat comparison is the product table, not a wiring diagram. Products Compared used public UK sources and notes on these listings. This is not a Gas Safe ruling and not a personal test. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Power | Receiver | Boiler interface | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  tado tado X wireless starter | 3 AAA included | Wireless Receiver X listed | OpenTherm or relay | 8.8 | about £129.99 | View offer |
 tado tado X wired add-on | 6 AAA included | Bridge X not included | OpenTherm or relay | 8.4 | about £79.99 | View offer | |
| Preis-Tipp |  KETOTEK KETOTEK boiler stat | Mains. Title says 220 V | No separate receiver listed | Dry contact, no voltage. Title says 3 A and 220 V | 8.2 | about £44.99 | View offer |
On this page
Decide if this is still a consumer control
Gas work and a room-stat swap are not the same job, and they meet when the case comes off. Gas Safe Register tells householders not to fit or move a gas appliance, and not to disturb gas-carrying parts or the combustion case. A later sign-off does not make unregistered gas work legal. The Health and Safety Executive's approved code L56 treats work on a consumer control, such as an electric thermostat or timer, as outside the gas-safety regulations when no gasway is broken. Competence still applies to the electrical side of what you touch. If you are changing a room head or a receiver on an existing circuit, and you are not breaking into the gas path, you are in that consumer-control description. If the job needs the boiler case open, you are in Gas Safe territory. A wireless sensor does not remove the wired receiver at the boiler. One installer site says that replacing a room thermostat on an existing circuit outside a bathroom is not itself notifiable under Part P, and that the boiler job is the gas work. That is their statement, not a ruling from this site. New cable or a new circuit is a different electrical job from reusing two labelled cores. Who may do the work is set out in who can fit a thermostat in the UK.
Identify the terminals before you loosen a screw
Volt-free and switched live must not be guessed from wire colour. Flameport's combi notes put it plainly: volt-free terminals must not see mains, switched-live terminals are a different two-wire or three-wire job, and you never join the two sets. Mains on a volt-free pair can damage the boiler board. That is why it looks like the old stat is not an identification. Read the boiler manual's external-controls page and the diagram in the stat's box together. A dry-contact output closes a call for heat and does not present 230 V on that pair. A switched-live stat expects a live feed and returns a live when the room is calling. If the old cores are unlabelled, or you cannot tell which pair is which, stop. Photograph the terminals before you disconnect anything, including any link that was already parked. The OpenTherm or relay page explains modulation. It does not give you terminal numbers, and neither does this one.
The sequence if the diagram matches
When the diagram matches, keep the order dull and short. Isolate the circuit at the fused spur or the breaker that feeds the controls, and prove it is dead before you separate a core. Photograph the old head, label each core with the terminal name from the old plate, and only then remove it. Fit the receiver or the wall plate to the same points the diagram names. Restore power only after the covers are back and no bare copper is proud of a terminal. Place the room sensor where it measures the room you actually live in. Common UK guidance, not a measurement from these listings, is about 1.5 m on an internal wall, out of sun and draughts, and not hidden behind curtains. Do not site it in a fight with a thermostatic radiator valve in the same room. Then join the app. Several tado reviews needed the 2.4 GHz network, with 5 GHz turned off for pairing. The tado X add-on still needs a Thread border router before the app can finish, which is a setup step, not a new cable in the wall. If the boiler does not fire, go back to the diagram rather than adding a link you cannot name.
Where people in these reviews had to stop
One KETOTEK buyer added a 3 A fused spur because that stat is mains-powered. If you do not already have a suitable supply at the wall, that spur is new electrical work, not a five-minute faceplate swap. A MincoHome review needed a deep back box and four wires. Forcing a mains head into a shallow two-wire box is how you crack the plate or leave cores crushed. A tado review only got the boiler to fire after normally open and normally closed were swapped, against the first instructions. tado's own relay note says the hardware terminal is normally open, that the app can change relay behaviour, and that normally closed is wrong if the stat sits on the boiler directly, while some underfloor systems need it. If heat stays on after a straight copy of the first screen, stop and use the maker's support rather than cycling every terminal. Another review ended with the app calling the boiler incompatible. That is the moment for the boiler maker or a registered engineer, not a second protocol you invent on the day. Also stop when an S-plan or Y-plan must keep stored hot water timed, because that is more than a single room call. The Wi-Fi room thermostat on a combi page is only for on-demand hot water.
Common questions
Can I install a Wi-Fi room thermostat myself in the UK?
You can change a consumer control on an existing circuit when no gasway is broken, which is the HSE line for an electric thermostat or timer. You still need to understand the terminals and isolate the supply. If the work opens the boiler, adds a circuit, or leaves you guessing at the volts, it is no longer that simple swap.
When is the job gas work?
It is gas work when you fit or move the gas appliance, disturb gas-carrying parts, or open the combustion case. Gas Safe says a later sign-off does not legalise unregistered gas work. Changing a room stat without breaking the gas path is the consumer-control side of the fork, not a licence to work inside the boiler.
What is a volt-free terminal?
A volt-free, or dry-contact, pair is a switch. The stat closes it to call for heat and does not put mains voltage on those two terminals. Flameport warns that putting mains on a volt-free combi pair can damage the board. Switched live is the other family, and the two must not be linked.
Where should the room sensor sit?
Use an internal wall at about 1.5 m, clear of sunlight, draughts, and curtains, so the sensor sees the room rather than a window or a fireplace. Avoid the same room as a thermostatic radiator valve that is also trying to control that space. That height is common UK guidance, not a figure measured on these products.
What do I photograph before I disconnect the old stat?
Photograph the terminals with the cores still in place, and note any link or spare core. Label each wire with the old terminal name before you lift it. Those pictures are what you compare with the new diagram if the boiler does not fire after the swap.
Why will the app not join my Wi-Fi?
On several of these listings the phone must see a 2.4 GHz network. A 5 GHz-only name will fail the join even when the wiring is correct. For the tado X add-on, the app also cannot finish until a Thread border router, such as Bridge X, is already on the account.
What if the boiler does not fire after the swap?
Isolate again, compare your labels with the diagram, and do not add an unlabelled core to make it go. A review only succeeded after normally open and normally closed were corrected, which is a maker's relay setting, not a cue to experiment. If the app then says the boiler is incompatible, contact the boiler manufacturer or a registered engineer.
Related pages
Sources
Public UK sources for Part L in England, Boiler Plus, and Gas Safe. Listings are the amazon.co.uk captures for these seven ASINs, not a live reload on 17 October 2026. Prices on amazon.co.uk move.
- Approved Document L (retrieved 17 October 2026)
- BEAMA heating-controls note (retrieved 17 October 2026)
- MHCLG circular, 3 April 2018 (retrieved 17 October 2026)
- HSE gas work (retrieved 17 October 2026)
- Gas Safe Register, home improvements (retrieved 17 October 2026)
- Which? smart thermostat buying guide (retrieved 17 October 2026)
- tado UK compatibility (retrieved 17 October 2026)
- Flameport combi thermostat terminals (retrieved 17 October 2026)