Malfunctioning thermostats

A faulty thermostat can cause unnecessarily high energy consumption.

To show you what it looks like when a radiator has a faulty thermostat, we have photographed two radiators, one which works as it should and another with a faulty thermostat.

The pictures are taken with a heat camera which registers temperature differences on surfaces in the room.

The picture above shows a radiator with an old thermostat which does not regulate the temperature on the radiator based on the room temperature but allows hot water to flow freely through the radiator.

The thermostat should in normal circumstances close off the flow to the radiator when the temperature in the room is sufficient. A malfunctioning thermostat can result in the room becoming far too warm and energy consumption becoming unnecessarily high. Seeing as the return temperature from the radiator is high, this can also impact on the degree of efficiency of the heating system which will be lower than otherwise.

You can test your thermostat by switching it off completely and feeling whether the radiator becomes cool. You can often hear when you turn the thermostat whether it is working or not. If it is working, you will be able to hear the water starting to circulate when you open up the thermostat.

The radiator in the picture above is in a system where a high temperature difference is required between the inflow and return. As the water flows through the radiator it cools down and the return temperature, at the bottom of the radiator, is almost 20° lower. The same heat effect is produced as with the picture above, but with a lower flow of radiator water. A lower flow means that the circulation pump’s energy consumption will be lower and that the system's heat source can work within a greater temperature range.

Photo: Mikael Söderström Rosén, KanEnergi