You bought a WiFi thermostat so the heating could run itself, not so you’d argue with it at 11 pm. The unit on your wall will hold a temperature all winter if you let it — but a static set-point is the most expensive way to run electric underfloor heating. Programming a WiFi thermostat through the Tuya app is what turns a dumb-on switch into a heating schedule that matches your actual day: warm when you are there, quiet when you are not. This guide walks through the onboarding, the weekly schedule, the floor-versus-air sensor choice, and the set-back habits that keep comfort without paying to heat an empty room.
Why Programming Your WiFi Thermostat Matters
An electric underfloor heating film, mat or cable is a resistive load: when the relay closes, it draws close to its rated wattage continuously until the room reaches set-point and the relay opens. A thermostat left on a fixed 21 °C around the clock will close that relay whenever the floor or room drops even a fraction below set-point, including the seven or eight hours you are asleep and the eight or nine hours you are at work. The heat output during those hours is comfort you are not using.
Programming works by cutting full-load hours, not by making the heating weaker. When you drop the set-point overnight (set-back) or pause it while the house is empty (away / holiday mode), the relay simply stays open for long blocks of the day. Industry guidance and field experience consistently report that scheduled set-back reduces underfloor heating runtime compared with an always-on comfort temperature, because the heating only calls for heat when the room needs it. Your actual saving depends on the insulation of the floor build-up, the outside temperature, the floor covering and your occupancy pattern — a well-insulated modern flat on a night tariff will behave very differently from a drafty tiled extension — so treat any headline percentage you see elsewhere as a rough expectation, not a guarantee. The mechanism, however, is unambiguous: fewer relay-on hours equals fewer kilowatt-hours.
The other benefit is comfort quality. A scheduled floor warms up to a gentle level by the time you get out of bed, rather than blasting on at full power after you remember the thermostat exists. Because thermal mass in a screed or tile floor takes time to respond, starting the heat before you need it — rather than after you are cold — is the single biggest comfort lever the app gives you.
What You Need Before You Start
Programming is faster when the wiring and sensor work is done first. Before you open the Tuya app, confirm the following, whether you are commissioning a K2M WiFi thermostat, a K9 colour-touch WiFi thermostat, or another model in the WiFi smart thermostat range:
- The thermostat is powered (AC 95–240 V for the K2M, AC 90–240 V for the K9) and the backlit LCD wakes up.
- The external NTC floor probe is connected and routed under the heating element, not left dangling at the wall box. The K2M ships with a 3 m floor probe; the K9 also ships with an external NTC floor probe used for floor-temperature limiting.
- You are on a 2.4 GHz WiFi network. Tuya-compatible thermostats do not join 5 GHz networks, so during pairing keep the phone on the 2.4 GHz band and temporarily move close to the router if pairing stalls.
- You have installed the Tuya Smart (or Smart Life) app and registered an account. The same Tuya account later links to Alexa or Google Home for voice control.
- You know your floor covering. Wood, laminate and LVT floors need a floor-temperature cap; tile and stone can run warmer. This decides which sensor mode you use (more below).
Tuya App Onboarding: Pairing Your K2M or K9
Both the K2M and K9 join your home network through the same Tuya pairing flow, so the steps below apply to either once the unit is wired and powered.
- Open the Tuya Smart app, sign in, and tap the + icon in the top right. Choose Add Device, then Climate / Heating Thermostat (the thermostat appears under small-home or climate categories depending on app version).
- Confirm the WiFi indicator on the thermostat is blinking rapidly. If it is not, hold the relevant network/pairing key on the faceplate until the WiFi icon flashes quickly (this is the fast-pair / EZ mode). The K2M uses its five touch keys (power, mode, timer, up, down); the K9 uses its on-screen MODE and TIME controls.
- Enter your 2.4 GHz WiFi password in the app. The thermostat joins the network, registers with the Tuya cloud, and appears as a tile in your device list.
- Rename the device to match the room, for example “Bedroom UFH” or “Kitchen Floor”. This name is what you will later use with voice assistants, so make it unambiguous.
- From the device tile you can now change set temperature, switch between manual and automatic mode, view the current room (and floor, if the probe is fitted) reading, and open the weekly schedule editor. Settings such as child lock, antifreeze mode and temperature calibration are in the device’s settings menu.
Pairing is a one-time step. After the unit is on your network, the schedule and mode live in the cloud and on the thermostat itself; if your internet drops, the K2M and K9 keep running their last weekly programme because settings are held in non-volatile memory with power-off memory, so a Wi-Fi or cloud outage does not leave you heating by accident — or unheated.
Building Your Weekly Schedule Step by Step
The K2M and K9 both use a 7-day programme with up to six time periods per day. In practice most people only need four to six blocks, and the app lets you copy a finished day’s schedule onto other days, which is where the time savings happen.
A sensible starting schedule for a typical working household:
| Period | Time | Target temperature | Why |
|---|---|---|---|
| Morning warm-up | 06:30 – 08:00 | Comfort (e.g. 21–22 °C) | Warm floor underfoot as you get up; starts before you need it because the floor has thermal mass. |
| Day set-back | 08:00 – 16:00 | Set-back (e.g. 16–18 °C) or off | House empty; maintain frost protection rather than comfort. |
| Evening comfort | 16:00 – 22:30 | Comfort (e.g. 21–22 °C) | Everyone home; floor at a usable temperature. |
| Night set-back | 22:30 – 06:30 | Night / eco (e.g. 16–18 °C) | Bedrooms rely on bedding; the bathroom or hallway can stay warmer if it gets cold. |
To set this in the app: open the device, enter the weekly-programme / timer screen, pick the day (or the weekday group), and add each time block with its start time and target temperature. On the K2M you can copy one day’s programme to other days; on the K9 you can define separate weekday and weekend programmes, so the late start on Saturday and Sunday is automatic. Save the programme, then switch the thermostat from Manual to Automatic (the MODE / M key on the unit, or the app mode switch). The clock on the thermostat must be correct for the schedule to fire at the right hour — check it after any power cut, although power-off memory normally preserves it.
Resist the temptation to over-programme. Four well-chosen blocks beat six fiddly ones you will never adjust. Revisit the schedule after the first two weeks: if a room is cold when you use it, start that block earlier; if a room is warm when empty, drop the set-back temperature further.
Floor Sensor vs Air Sensor: Which Mode to Choose
This is the setting that most often gets left on the wrong value, and it matters for both floor safety and comfort. The K2M and K9 each carry an internal air sensor and accept an external NTC floor probe. The control mode decides which reading the thermostat acts on:
- Floor sensor control (floor probe as the primary sensor): the thermostat cycles the heating to hold a target floor temperature. This is the correct mode under tile, stone and concrete, where you want the radiant floor to sit at a gentle skin temperature and the room warms by radiation. It is also the required safety mode under wood, laminate and LVT, where a maximum floor limit (the K9 commonly uses a 27–35 °C floor cap) protects the flooring from overheating and drying out.
- Air sensor control (internal room sensor): the thermostat holds the air temperature where the wall unit is mounted. Use this when comfort is judged by room air temperature and the floor build-up is robust (tile over screed), or when the NTC floor probe is fitted purely as a limiting device rather than the primary control.
- Air control with floor limiting: the common best-of-both setup — the thermostat holds the room comfort temperature using the internal air sensor, but cuts out if the external NTC floor probe exceeds the configured maximum. This is how you protect a wooden floor while still heating to a room set-point. The K2M’s “optional external NTC floor temperature-limiting probe” and the K9’s configurable floor cap are exactly this function.
Match the mode to the finish, not to habit. If you are unsure, fit the floor probe, set a conservative floor maximum, and let the room sensor run comfort mode; you can always lower the floor cap further. A floor probe that was disconnected or never connected leaves the thermostat guessing from air temperature only, which is the usual cause of either an over-warm wooden floor or an under-heated room.
Voice Control: Alexa, Google Home and Beyond
Once the thermostat is bound in the Tuya app, voice control is an extra on top of — not a replacement for — the schedule. The K9 page explicitly supports Alexa, Google Home and Yandex Alice through the Tuya skill; the K2M page confirms Alexa and Google Home voice control after the Tuya link. To enable it, open your Alexa or Google Home app, add the Tuya / Smart Life skill, sign in with the same Tuya account, and discover devices. The room names you set during pairing become the voice commands, for example “Alexa, set Kitchen Floor to 21 degrees.”
Voice control is genuinely convenient for ad-hoc overrides — turning the bedroom warmer when you are already in bed, or knocking the heating down when you leave for the weekend — but treat it as a manual override. The weekly programme still runs underneath, so a voice change holds until the next scheduled block, unless you hold it in the app. Child lock on the wall keys does not disable the app, so voice control remains available even when the physical keys are locked against small hands.
Set-Back, Eco and Away Tips That Cut Runtime
Programming lays the schedule, but the real energy savings come from how aggressively you use the lower set-points and the holiday/away functions:
- Night set-back, not night off. Dropping to 16–18 °C overnight keeps frost at bay and avoids a cold morning warm-up load; switching fully off on a poorly insulated floor means a much bigger, longer reheat the next morning, which can cost more than it saved.
- Use the holiday / away mode. Both the K9 (explicit holiday mode) and the antifreeze mode on the K2M hold a low frost-protection temperature while you are travelling, rather than either a comfort set-point or a cold-down-to-zero risk. Set it from the app before you leave.
- Zone room by room. Each thermostat controls one circuit. There is no need to hold the guest bedroom at 21 °C for three weeks a year; give it a lower set-back or switch it off in the app while the living room stays comfortable. Per-room control is why multi-zone electric systems scale with how you actually use the house, not with the floor area.
- Pre-heat, don’t overshoot. Because a tiled or screeded floor has thermal mass, start the comfort block 30–60 minutes before you arrive rather than cranking the temperature up at the door. A longer, gentler call for heat beats a short high-demand spike.
- Calibrate the display. The K9 offers a −9 to +9 °C calibration offset and the K2M supports display recalibration against a reference thermometer. If the screen reads 21 but a known-good thermometer says 19, every schedule you programme is quietly off by two degrees. Calibrate once and forget it.
Off-Peak Tariffs and Timer Programming
If you are on a time-of-use or Economy-7 style tariff, the weekly timer is where you turn cheaper overnight electricity into lower bills. The idea is to let the floor mass absorb heat during the cheap overnight window and ride through the expensive daytime period on stored heat, then only top up during another cheap window. With a Tuya thermostat you simply schedule the comfort/warm-up blocks to coincide with the off-peak tariff periods and set a set-back — not full off — through the peak-rate hours, sized to how long your specific floor build-up holds temperature.
Because the right set-point depends on slab type, insulation and the tariff rate, work from measured runtime rather than a guess: run one week as programmed, read the kWh on your meter, and nudge the peak-time set-point down until the room stays comfortable. For more on how electric underfloor heating interacts with off-peak pricing, see our guide to off-peak electric underfloor heating. If you are still sizing the load that each 16 A circuit can switch, the underfloor heating calculator helps match the wattage to the room and the relay rating.
Compatibility: Film, Mat and Cable Heating
Programming is only useful if the thermostat can actually switch the load you have. The K2M relay is rated 16 A resistive, suitable for up to roughly 3600 W of electric underfloor heating; the K9 is offered in 16 A (typical film and mats), 25 A (K9H25A backplate, higher electric loads) and 3 A dry-contact versions for water underfloor loops or a wall-hung gas boiler. For larger multi-zone projects you switch the heating through an external contactor and let the thermostat drive the contactor. On the heating side, the same controls are equally at home with electric heating film (graphene/PET film for tile, laminate and wall panels), with heating mats (encapsulated cable on a mesh for tiled wet areas), and with loose heating cable laid in screed — the relay does not care which element it switches, as long as the total resistive load is within the rating and the NTC floor probe is fitted.
If you are specifying thermostats as part of an OEM or private-label heating project, the K2M and K9 are both available with custom fascia colour, logo on the display, multilingual firmware and private-label packaging through our OEM/ODM thermostat service.
Troubleshooting Common Programming Issues
- The schedule does not fire at the right time. The thermostat clock is wrong or the unit is still in Manual mode. Check the clock in 24-hour format and press MODE to Automatic. After a power cut, confirm the clock restored correctly.
- The room is cold even though the schedule says heating. Check which sensor is active. If you are on air control with the probe disconnected, or the floor limit has been set too low, the relay may be cutting out early. Confirm the floor-probe mode and the floor maximum in the installer/settings menu.
- The thermostat keeps dropping offline in the app. Tuya thermostats need a stable 2.4 GHz network. Move the router or add a 2.4 GHz range extender; avoid placing the unit inside a metal wall box behind a foil-backed insulation board, which attenuates the Wi-Fi signal.
- Voice control works only sometimes. The Tuya skill link expired after a password or app update. Re-link the Tuya skill in Alexa/Google Home and re-discover devices.
- A wooden floor feels too hot. Lower the configurable floor-temperature limit (the K9 caps are typically set in the 27–35 °C range) and keep the NTC probe fitted; this is a floor-safety setting, not a comfort set-point.
Frequently Asked Questions
How do I program a WiFi thermostat in the Tuya app?
Pair the thermostat over 2.4 GHz WiFi in the Tuya Smart or Smart Life app, open the device tile, enter the weekly-programme / timer screen, and add time blocks with a start time and target temperature for each period. Both the K2M and K9 support up to six periods per day, with weekday and weekend programmes, and you can copy one day’s schedule onto others. Save the programme, then switch the unit from Manual to Automatic mode.
What is a good weekly schedule for electric underfloor heating?
A common starting point is a morning comfort block (around 06:30–08:00), a daytime set-back or off block while the house is empty (08:00–16:00), an evening comfort block (16:00–22:30), and a night set-back to around 16–18 °C. Because a tiled or screeded floor has thermal mass, start the comfort block 30–60 minutes before you actually need the warmth.
Should I use the floor sensor or the air sensor?
Under tile or stone you can control on the floor probe directly; under wood, laminate or LVT you should use the air sensor for room comfort with the external NTC floor probe as a temperature limiter (commonly capped at 27–35 °C on the K9). The K2M ships with an external NTC floor-limiting probe for exactly this protection.
Does the K2M or K9 work with Alexa and Google Home?
Yes. Both thermostats connect through the Tuya Smart / Smart Life app over 2.4 GHz WiFi; the K2M supports Alexa and Google Home voice control after the Tuya link, and the K9 additionally works with Yandex Alice. The voice commands use the room names you give each device during pairing.
Will a WiFi thermostat save me money on underfloor heating?
Programming and set-back reduce the number of hours the heating runs at full load compared with an always-on comfort temperature, and scheduling is widely reported to cut electric underfloor heating runtime. Your actual saving depends on insulation, floor build-up, outside temperature and occupancy, so treat any specific percentage as a rough expectation rather than a guaranteed figure. The measurable mechanism is fewer relay-on hours.
What happens if the WiFi or power goes out?
The thermostat keeps running. The K2M and K9 store their schedule, calibration and mode in non-volatile memory with power-off memory, so after a power cut they resume the last programme automatically. If the WiFi drops, the unit continues following its weekly schedule locally; you simply cannot adjust it from the app until the network returns.
Related Products & OEM Inquiries
Looking for a Wi-Fi thermostat you can program confidently or a factory-direct OEM/ODM partner? Explore our smart thermostats and floor-sensing controls, then request a quote for your project — we supply distributors, installers and brands in 50+ countries.