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Thermostats: How do they work, what types are there, and are they necessary?

Integral H with Danfoss thermostat
Hudevad Integral Horizontal with Danfoss RA2000 thermostat


Thermostats are smart. They ensure energy savings and give the room the desired temperature for your well-being and comfort.

A thermostatic system usually consists of 2 parts – a radiator valve that sits in the radiator itself, through which the hot water flows. The valve can be preinstalled in the radiator from the factory, or it will be fitted by the installer. The setting on the valve is adapted to the size of the radiator and the room and is often not something you touch yourself. The thermostat is mounted on top of the valve and is the part we control ourselves - when we set the desired temperature in the room.


But are thermostats necessary?

Without a thermostat, your radiator will still emit heat if the heat source is on. If the thermostat is not fitted or is broken, the hot water in the radiator will flow at full speed, as the valve is fully open. You will therefore be exposed to very uncomfortable temperatures and improbably high heating bills. The radiator will run constantly instead of regulating itself as needed. In addition, it can also lead to overheating of the radiator and system components, which can damage the entire heating system.

So no, a thermostat is not absolutely necessary, but it can be both hot and expensive to do without it.


How does a thermostat work?

Basically, the thermostat measures the temperature in the room and compares it with the desired setting. If the temperature is lower than the desired setting, the thermostat will activate the valve in the radiator, which will open the flow of hot water and thereby increase the temperature. When the temperature reaches the desired setting, the thermostat will deactivate the radiator to maintain the temperature at the desired level.


More than one type of thermostat

Thermostats can be both mechanical and electronic.

Thermostat Piso
Hudevad Piso with Danfoss RA2990 thermostat

Mechanical thermostats use an actuator that expands and contracts to open and close a switch when the temperature in the room changes. When, for example, it gets warm in the room, the actuator expands and presses on the spindle that is connected to the valve inside the radiator, which thereby closes off the flow of hot water. When the temperature in the room has dropped, the actuator contracts and thereby opens the inflow of the hot water in the radiator, so that the room can become warm again.

The new smart, electronic or digital thermostats as they are also called, use a temperature sensor and a computer to calculate when the radiator should be activated or deactivated. What the new thermostats have in common is that they can control the temperature in the room or the whole house based on criteria you determine yourself - and usually control via an app on your smartphone.

Hudevad Danfoss Ally
Hudevad sells the Danfoss Ally Smart thermostats

The thermostats can be mounted directly on your current radiators, even if they are not of recent date. You can then control e.g., day and night temperature, whether the radiator should shut down if you open a window, regulate the temperature when you are on holiday and a wide range of other options that make it possible to lower the heating bill.

At Hudevad, we have both mechanical and electronic thermostats that you can pair with your radiators.


When is it worth replacing your thermostats?

Newer thermostats are cheaper to run as they are more energy efficient. But it is not free to buy new smart thermostats, which typically cost between 70-300 £ each. So, when is it appropriate to replace them?

A good rule of thumb is that if your thermostats are older than the year 2000, it is probably time to replace them. You can thus get a return on your investment in 3-4 years. If, on the other hand, you replace thermostats that are only 10 years old, you investment will be returned in approximately 8 years.


Aesthetic advantage of replacing the old thermostats

In addition to the practical, climate and economic aspect, there is also an aesthetic advantage to replacing old thermostats.

New thermostats have a more sophisticated and stylish design than the old thermostats. The new smart thermostats do not stand out in the same way in a modern home and will complete the decor.

So, give your thermostats some attention and consider whether it might be time to replace them.

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