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Setting a thermostat correctly

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If it is too cold in the room, most people reach for the white thermostatic head on the radiator and turn it up, or to the left to be more precise. If the temperature is felt to be above the required limit, the same thermostatic head is turned to the right. For most, this is the classic way of adjusting a thermostat correctly. But what exactly happens when you turn the thermostatic head? And is there another way to achieve a comfortable temperature?  


The function of the thermostat in detail

When talking about a thermostat, most people mean the analogue, mechanical model. This essentially consists of three parts:

  • Thermostatic head: visible casing on which the numbers for the thermostat setting are located.  
  • Temperature sensor: usually a liquid that changes in volume depending on the room temperature.
  • Thermostatic valve: control pin located between the radiator and the thermostat.

When the thermostat is opened up, the control pin is retracted. As a result, more heating water flows from the heating pipe into the radiator. The temperature increases. Conversely, when less heating water enters the radiator, heating of the room gradually stops.


Thermostat sensor and its task

The task of the thermostatic valve or the control pin is therefore clear: it regulates the throughput of the heating water from the heating pipe into the radiator. But what does the temperature sensor do?

As the name suggests, the temperature sensor measures the room temperature and reacts to it. The room is therefore not heated continuously after the thermostat is opened up, but instead is heated up to a certain value, for example 20  degrees Celsius. How hot it should get in the room is determined by the occupants by adjusting the thermostatic head. The latter is traditionally marked with the numbers one to five.

The numbers on the thermostatic head

Even if there are no exact degree numbers on the thermostatic head, the room temperature can be easily regulated. Because the numbers on it correspond to a certain temperature. The infographic on the left illustrates this. It also shows recommended temperatures for different living spaces and provides information about the meaning of typical symbols: sun (standard setting), moon (night setback) and snowflake (frost protection). The frost protection setting is not used to increase the room temperature. It merely prevents the water in the heating pipes from freezing, and thus causing damage, in cold weather.  

Room temperature when setting the thermostat

Setting a thermostat correctly also means heating each room differently. After all, it doesn't have to be equally warm everywhere. There are standard values that occupants and homeowners can use as a guide when adjusting the space heating. These are:

  • Living room: 20 to 22 degrees Celsius
  • Bedroom: 16 to 18 degrees Celsius
  • Hallway and kitchen: 18 degrees Celsius
  • Children's room: 22 degrees Celsius
  • Bathroom: 23 to 24 degrees Celsius 

Since the perception of heat is subjective, everyone can of course decide for themselves how warm they want it. For economical and ecological reasons, however, it is worth paying attention to the right temperature. Because reducing the temperature by just one degree Celsius in all rooms can reduce heating costs by up to six percent – at least in an older building. 

Tips: What to look out for

As a rule, the room temperature can be easily adjusted via the thermostat on the heater. However, there are measures that help to ensure that temperature control is a smooth process that also saves energy.

The thermostat is set correctly, but the preferred temperature is not reached in the room. One possible cause is that it is covered by curtains or furniture. If the heat cannot escape, it accumulates. As a result, the sensor element assumes a higher temperature and reduces the heating water flow before the required temperature is actually reached. Radiator niches and an insufficient distance between the window sill and the thermostat can also affect the regulation process. This same applies to constant draughts. However, the latter results in the heating water flow being increased.

In order for the heating circuit pump to work efficiently and distribute the heat evenly throughout the house, the entire heating system must be set up correctly. Hydronic balancing lays the groundwork for this. Based on this, the individual radiators are adjusted so that they receive the necessary amount of heating water. However, this is only possible with pre-adjustable heating thermostats. If old models do not have this function, replacing them can help save heating energy and reduce costs.

You can find more tips on this topic in our guide "Saving energy and reducing heating costs" and in the"FAQs on heating et al".

Types of thermostats

As already mentioned, most people think of the classic white thermostat when they hear the term thermostatic head. For some years now, there have been modern variants that differ primarily in their range of functions. These include electric wireless thermostats and digital, programmable thermostats. These give occupants the option of setting their required temperature from the comfort of their couch. Digitally programmable heating thermostats can even be controlled from a smartphone or tablet using an app. In this way, the room temperatures can be regulated even when the occupants are absent. Most of these advanced thermostats can be installed without specialist knowledge. Anyone wanting to replace their outdated or even defective analogue thermostats should consider these new devices.

Important: if you live in a rented house and replace the thermostats, you should keep the old ones, because they still belong to the landlord.


Room thermostat for individual room control

In addition to the thermostatic radiator valve, there is also the room thermostat. This enables individual settings for separate rooms. Individual room control, as it is called, not only makes sense economically, it is also a requirement of the Gebäudeenergiegesetz (GEG). It's important to consider the positioning of the room thermostat when installing it. It should not be exposed to sunlight or intense heat from a radiator. If it is, the room temperature it registers will be too high. A location that is too cool should likewise be avoided. Otherwise, the system will attempt to achieve a temperature that is too high.

Heating control unit instead of thermostat

Unlike occupants, system owners have other options for setting their required temperature. This is because modern heat generators have intelligent control systems that allow versatile remote control. The heating output, for example, can be individually adjusted to the heat demand in just a few simple steps. As an option, the system can even be enabled for your trusted heating contractor. This enables the contractor to detect faults in the heat generator and rectify them promptly – without the system owner noticing. This is made possible by the innovative Viessmann apps.

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