When your underfloor heating thermostat is not working correctly, it doesn't always mean the device needs to be replaced. In this guide, we look at the most common problems, such as a floor that isn't heating up, overheating, a faulty floor sensor, and a broken relay. We also provide practical tips for troubleshooting and choosing the right solution.
1. The underfloor heating does not reach the desired temperature
If the floor heats up but does not reach the expected temperature, the fault might not be in the underfloor heating thermostat. Instead, the issue is often a weak heating cable (insufficient wattage) or a low water temperature in the pipe system.
2. The underfloor heating does not heat up at all or overheats
If the underfloor heating thermostat is not working and the floor remains completely cold or gets too hot, check the following:
Are the thermostat lights on, and is there power? Check if power is reaching the thermostat. If there is power, but the indicator lights or screen do not turn on, the thermostat might have suffered a power surge (e.g., from a thunderstorm) and needs to be replaced.
Testing the power output: If the lights are on and turning the dial seems to switch the heating on or off: remove the thermostat from the wall and check if there is voltage at the thermostat's output terminals. If voltage appears when you turn the dial, the fault lies in the heating cable or the actuator. If there is no voltage at the output, the thermostat's output relay is worn out, and the underfloor heating thermostat needs to be replaced.
The thermostat is clicking rapidly: If the underfloor heating thermostat clicks (the relay) at a frequency of about once per second, it is technically repairable, but usually, it is not worth the time and effort. It is more practical to buy a new thermostat.
Overheating issues: If the underfloor heating overheats, even when the indicator lights or screen claim the heating is turned off, the fault could be a stuck output relay. In this case, the thermostat needs to be replaced.
Faulty floor sensor: If the heating does not turn on or refuses to turn off when adjusting the dial or screen, the fault might be in the floor sensor. If the floor sensor has been exposed to moisture (e.g., due to poor waterproofing) and short-circuited, the heating won't turn on, the floor stays cold, and the floor sensor needs replacing. If the heating refuses to turn off, the sensor is likely short-circuited.
Compatibility issue: This problem can also occur when replacing an old thermostat with a new one but leaving the old floor sensor in the floor. Sensors from different manufacturers have different parameters and may not be compatible. The solution is to replace the floor sensor as well. If the sensor cannot be replaced, you need a thermostat that works with all types of floor sensors, such as the Heatline HL-44.
Safety features: Most modern thermostats also have a built-in safety function that turns off the heating if the floor sensor fails, preventing overheating and excessive energy consumption.
Summary
Before buying a new underfloor heating thermostat, go through the checks mentioned above—often, the problem can be solved with a simpler fix than a complete replacement. If you have any questions, contact us: info@heatline.ee or call +372 5303 3990.