What is this?
The thermostat is the control centre for your electric underfloor heating. It reads the floor temperature sensor and switches the heating on and off to maintain the set temperature. When the thermostat fails, the heating may not turn on at all, may run continuously, or may display error codes.
Common causes
- Failed floor temperature sensor (most common thermostat-related fault)
- Blown fuse in the spur supplying the thermostat
- Thermostat internal electronics failure
- Loose wiring connections behind the thermostat
- Incorrect thermostat settings or programming
- Incompatible replacement thermostat
Is it dangerous?
A faulty thermostat is not dangerous in itself. However, if the thermostat fails in a way that the heating stays on constantly, the floor could overheat. If the floor feels unusually hot, switch the heating off at the isolator and call an electrician.
Can I fix it myself?
Check the fuse in the spur feeding the thermostat. Try resetting the thermostat to factory settings using the manual. Check the programming and mode settings — many thermostats have holiday or frost-only modes that prevent normal operation. Replace the batteries if it is a wireless thermostat.
When to call an electrician
Call an electrician if the thermostat display is blank despite having power, if it shows a sensor error, if the heating runs constantly and will not turn off, or if you need a replacement thermostat installed.
What will an electrician do?
Test the supply to the thermostat
Measure the floor sensor resistance and compare to the manufacturer's specification
Check thermostat output to confirm it is switching the heating
Replace the floor sensor or thermostat as needed
Program and commission the new thermostat
Typical cost
£80 – £220
Thermostat replacement including a new unit typically costs £120-£200. Floor sensor replacement is cheaper if the sensor cable is accessible.
