Short answer: Control most underfloor heating rooms on air temperature, and add a floor probe as a limit when the floor finish has a maximum temperature. Wood flooring makers commonly set 27°C at the board surface, and vinyl makers 27°C at the adhesive line, which is lower than the 29°C design limit in BS EN 1264 for occupied areas. Electric mats should always have a floor probe. On a Heatmiser neoStat V3 the floor limit can be set from 20 to 45°C and is 28°C out of the box.
A floor probe is a £8 to £13 part, but it decides whether a wood floor stays flat and whether a room gets the heat it needs. Set the limit too high and you risk the finish. Set it too low and you cap the output of the whole floor.
This guide covers the sensing modes, the right limit for each finish, how to fit and test a probe, and where the air sensor should go. For how thermostats and wiring centres work in general, see Underfloor heating thermostats explained.
What sensing modes can a UFH thermostat use?
A floor-sensing thermostat can usually read the air, the floor, or both, and you choose the mode in its setup menu. On the Heatmiser neoStat V3, the sensor selection setting has five options:
| Setting | Controls on | Floor limit |
|---|---|---|
| 00 Built-in (default) | Room air at thermostat | No |
| 01 Remote air | Room air at remote sensor | No |
| 02 Floor only | Floor temperature | Floor is the target |
| 03 Built-in + floor | Room air at thermostat | Yes |
| 04 Remote air + floor | Room air at remote sensor | Yes |
In modes 03 and 04, the thermostat heats to the room setpoint but stops calling for heat if the floor reaches the limit, even if the room is still cold. That is the mode to use under wood and vinyl.
When should I use air sensing, floor sensing or both?
Use air sensing for comfort, floor sensing where a warm floor is the point, and both where the finish needs protecting.
| Room or finish | Mode | Why |
|---|---|---|
| Tiled living room, kitchen | Air | Room comfort |
| Engineered or solid wood | Air + floor limit | Protect boards |
| LVT or sheet vinyl | Air + floor limit | Protect adhesive |
| Tiled bathroom or en-suite | Floor or air + limit | Warm floor wanted |
| Conservatory | Floor | Sun fools air sensor |
| Electric mat or cable | Floor or air + limit | Probe always fitted |
Floor-only mode suits rooms where the air reading is unreliable. In a conservatory, sun can push the air sensor to setpoint while the floor goes cold, so controlling on the floor keeps the slab at a steady temperature.
What floor temperature limit should I set?
Set the limit to the lowest of two figures: the floor finish maker's maximum, and the BS EN 1264 design limit for that area. Check your own flooring instructions, because they override any general figure.
| Floor finish | Typical maximum | Where it applies |
|---|---|---|
| Tile or stone, living areas | 29°C | Surface (EN 1264) |
| Tile or stone, bathrooms | 33°C | Surface (EN 1264) |
| Edge zones by outside walls | 35°C | Surface (EN 1264) |
| Wood flooring | 27°C | Board surface |
| Vinyl, LVT, sheet | 27°C | Adhesive line |
| Carpet | Maker's figure | Check underlay too |
The wood figure comes from a wood flooring maker's underfloor heating guidance, which says the board surface should not exceed 27°C. The vinyl figure comes from a vinyl flooring maker, which says the adhesive line should never exceed the industry agreed maximum of 27°C. The neoStat V3 default of 28°C is therefore 1°C too high for most wood and vinyl floors, so lower it during commissioning.
The probe sits in the screed or tile bed, closer to the heat than the floor surface. In practice that means a probe limit set to the finish maker's figure errs on the safe side. If a floor feels cooler than expected, check the surface with an infrared thermometer before you raise the limit, and never go above the finish maker's maximum.
How much heat do I lose by limiting the floor temperature?
Floor output depends on how much warmer the floor surface is than the room, so a lower limit means less heat. A manufacturer handbook based on EN 1264 uses a heat transfer coefficient of about 11.1 W/m²K, which gives these figures for a room at 20°C:
| Floor surface | Above room | Approx. output |
|---|---|---|
| 25°C | 5K | 56 W/m² |
| 27°C | 7K | 78 W/m² |
| 29°C | 9K | 100 W/m² |
Worked example. A 20m² lounge with engineered oak, limited to 27°C, can give about 20 x 78 = 1,560W. If the room's heat loss is 1,800W, the floor alone won't keep up on the coldest days, and raising the limit is not the answer. Improve the insulation, reduce pipe centres or add a heat emitter instead. See Heat loss and UFH output to check a room before you choose the finish.
How do I install a floor probe?
Fit the probe in a conduit, midway between two pipes or cable runs, in an area that represents the floor as a whole. The conduit means you can pull out and replace a failed probe later without lifting the floor.
- Pick the spot. Choose an open area at least a step in from the walls, away from doorways, the manifold pipe runs, and where rugs, beds or kitchen units will go.
- Run the conduit. Lay a length of conduit from the thermostat back box down the wall and into the floor zone. Seal the floor end so screed or adhesive can't get in.
- Place it between the heat. Position the probe tip midway between two pipes, or between two runs of heating cable. Never lay it on top of a pipe or across a cable, as it will read the heat source, not the floor.
- Test before you cover it. Measure the probe's resistance and connect it to the thermostat to confirm a sensible reading before any screed, adhesive or tiles go down.
- Record where it is. Mark the probe position on the floor plan and photograph it, so the next person can find it.
- Set the mode and limit. At commissioning, choose the sensing mode and set the floor limit for the finish.
The MaxHeatUFH 10K floor probe has a 3m cable, which reaches from a typical floor zone to the thermostat back box. Heatmiser recommend fitting their temperature sensor probe inside a conduit, laid between the heating cables or loops.
Which floor probe works with my thermostat?
Use the probe type your thermostat is designed for. Most floor-sensing UFH thermostats use a 10K NTC probe, where the resistance is about 10kΩ at 25°C and rises as the probe gets colder.
- neoStat V3: works with 10K, 12K and 15K NTC probes, so it can often reuse an existing probe in a retrofit.
- neoStat-e and Slimline-E: a floor sensor comes in the box. Keep a 10K floor probe as a spare.
- neoStat WiFi, Edge and Touch: support floor sensing, but the probe is sold separately.
- DS1 and DS1-L: no floor sensor input. Use a different model if the floor needs a limit.
A probe with the wrong resistance curve will still give a reading, but the reading will be wrong. Check the thermostat manual before reusing an old probe.
Where should the air sensor go?
The air sensor should read the room's true temperature: typically about 1.5m up an inside wall, out of direct sun and away from draughts, appliances, radiators and outside doors. If the thermostat can't go there, use a remote air sensor and put the thermostat somewhere convenient.
| Remote sensor | Best for | Price |
|---|---|---|
| Thimble sensor (wired) | Discreet, up to 20m cable | £17 |
| Sensor probe + housing | Wired air sensing on a wall | £8 + £8 |
| Wireless air sensor | No cable, averaging | £18 |
The Heatmiser Edge can pair up to 16 wireless air sensors within 40m and use the average reading. That helps in large open plan rooms where one corner runs warmer than another. A neoStat V3 can use a wireless air sensor through a neoHub.
How do I check if a floor probe has failed?
Disconnect the probe from the thermostat and measure its resistance with a multimeter. A working 10K NTC probe reads around 10kΩ at 25°C and a higher value when cooler. An open circuit, a short, or a figure far from the expected value means the probe or its cable is faulty.
- Look at the floor temperature the thermostat shows. A reading stuck at one value, or far from what an infrared thermometer shows on the floor, points to the probe.
- Isolate the thermostat and disconnect the probe wires.
- Measure the resistance across the two probe wires.
- If it is faulty and fitted in conduit, pull it out and feed in a new one. If there is no conduit, switch the thermostat to air sensing and make sure the flow temperature is low enough to protect the floor finish without a limit.
If the floor is cold but the probe is fine, the fault is elsewhere. Work through Underfloor heating not getting warm.
Products for this job
- 10K floor probe for UFH thermostats (3m): £13
- Heatmiser temperature sensor probe: £8
- Heatmiser thimble sensor: £17
- Heatmiser wireless air sensor: £18
- Heatmiser sensor probe housing: £8
- Heatmiser neoStat V3 smart thermostat: £77
- Pipe conduit (25m): £17
- All control accessories
Prices inc VAT, October 2026. Related guides: Heatmiser neoStat vs neoAir vs Slimline, UFH under tiles, LVT, laminate, wood and carpet and Electric UFH thermostats and 16A loads.
Planning UFH under wood or vinyl? Design it free with MaxHeatUFH ProLoop. Add your rooms and floor finish, and get a loop design and full kit list with prices, including the thermostats and floor probes for each zone. Start your design
Frequently asked questions
Do I need a floor probe for water underfloor heating?
Not in every room. Tiled rooms are usually controlled on air temperature with no probe. Add one under wood, vinyl and LVT, in conservatories, and anywhere the floor finish has a maximum temperature.
What should I set the floor limit to for engineered wood?
Wood flooring makers commonly set 27°C at the board surface. Check your own flooring instructions and set the thermostat floor limit to that figure or lower.
Where should the floor probe go?
In a conduit, midway between two pipes or cable runs, in an open area that won't be covered by rugs or furniture. Never on top of a pipe or touching a heating cable.
Can I fit a floor probe after the floor is laid?
Not inside the screed or tile bed. If no probe was fitted, control the room on air temperature and keep the flow temperature low enough for the finish, or ask your installer about a surface or remote sensor.
Why does my thermostat show a higher floor temperature than the floor feels?
The probe sits in the screed or adhesive bed, closer to the pipes or cable than the surface. The surface is usually a little cooler than the probe reading.
What does 10K mean on a floor probe?
It is a 10K NTC thermistor, which has a resistance of about 10kΩ at 25°C. The resistance falls as it warms and rises as it cools, and the thermostat converts that into a temperature.
Can a floor limit stop my room getting warm?
Yes. At a 27°C floor limit and a 20°C room, a floor gives roughly 78 W/m². If the room needs more than that, it will stay below setpoint on cold days.
Sources: Heatmiser neoStat V3 datasheet, Danfoss UFH handbook (EN 1264 surface temperatures and output), Junckers: underfloor heating with wood floors, Altro: flooring and underfloor heating