What to Do If the Room Is Warm but the Floor Is Cold with Infrared Underfloor Heating?

If with infrared underfloor heating the room air is already warm but the floor still feels cold, the most common cause is a too-low limit on the thermostat's floor sensor: the heating switches off before the surface of the covering has warmed through. The solution is in the thermostat's service menu – the upper limit of the floor sensor must be raised to a higher value that suits the covering.

Why does the floor stay cold if the air is already warm?

With infrared underfloor heating the thermostat measures in two places: in the room air and at the sensor built into the floor. At handover our installers set, according to the covering, up to how many degrees the floor temperature may rise at the sensor. This setting may nevertheless need to be changed later:

• it turns out that with the given limit the heating cannot warm the floor enough;
• there was a power cut;
• the thermostat restarted for any reason and the value went back to the factory setting.

A simple example: you would like 23 degrees in the room, but the floor sensor limit is also set to 23 degrees. The floor therefore cannot be warmer than this at the sensor – and the surface felt with the soles of your feet remains even cooler.

The sensor measures something different from what your feet feel

The floor sensor lies on the surface of the heating film, under the concrete or the laminate flooring. When you walk around the home you feel the top layer of the floor – and there can be a difference between the two. That is why you sometimes have to experiment: raise the lower limit gradually until the temperature on the walking surface is pleasant and comfortable. Keep to the covering manufacturer's instructions meanwhile.

• Parquet floor: the 35-degree limit seen in the video may still be suitable for parquet.
• Heating embedded in concrete: here even 40–45 degrees can be set. The concrete layer above the film can be so thick that with 40 degrees measured under the concrete, the surface you walk on is only 23 degrees.

Our topic page describes the operation and layer structure of electric underfloor heating in more detail; and our article on coverings that suit underfloor heating covers how coverings transfer heat.

Raising the floor sensor limit step by step

The steps apply to the thermostat shown in the video; on other models the numbering of the menu items may differ. How to enter the service menu is shown in our video article on calibrating the thermostat.

1. Open the service menu: the word "service" appears on the display.
2. Use the M button to page to menu item 4, and check how many sensors the thermostat monitors. "IN" means only the sensor built into the device – we do not use this –, "OU" only the external one, that is the floor sensor, and "AL" both. For home heating the aim is to use the two sensors together.
3. Page on to menu item 9: here you see at how many degrees the heating regulates down according to the floor sensor. Raise this value with the arrows.
4. Switch the thermostat off – switching off saves the setting.

If the floor sensor is not the problem

With ceiling heating a similar symptom is caused by other limits – our video on ceiling heating covers this. In a newly built house, the cold floor may also come from still-damp concrete: here is how to recognise it. A detailed description of the sensor modes and of the maximum adjusted to the covering is in our guide to setting the floor sensor.