If you notice that your home struggles to reach the set temperature of 21 and often stays around 19.5-20, before thinking there might be a malfunction, it could be due to incorrect boiler temperature settings.
In fact, with a thermostat in relay mode, you need to manage two different temperatures:
- Boiler-selected temperature: This allows you to decide how hot to heat your radiators, or underfloor heating.
- Ambient temperature set on the thermostat: This lets you regulate the room temperature
Obviously, these two temperatures are different, for the room we might choose 19-20 degrees as desired, while the boiler temperature will be:
- For cast iron radiators: Start with 45 degrees in autumn, increasing by five degrees as winter intensifies, up to 60 degrees
- For aluminum radiators: Start with 50 degrees in autumn, increasing by 5 degrees up to 65 degrees.
- For underfloor heating: Due to its high thermal inertia and more distributed heat diffusion, start with 24 degrees in autumn, increasing by two degrees at a time.
Underfloor heating then takes at least a day to stabilize.
Correct Settings for Radiator Heating
Start with the thermostat to determine if the boiler temperature needs to be raised or lowered. If the outside temperature drops, radiators may not heat the room sufficiently to reach the desired 19-20 degrees. In this case, you need to raise the boiler temperature by a maximum of 5 degrees more than the set value.
As a result, radiators will heat more, warming up the room, and the thermostat will pause the boiler.
Temperature for Cast Iron Radiators
If you have cast iron radiators, for instance in autumn, start with a heating temperature of about 45 degrees. In full winter, use a temperature of 55 degrees to compensate for common heat losses in your apartment.
Temperature for Aluminum Radiators
If you have aluminum radiators, this material requires a higher temperature to be effective. Start with a heating temperature of about 50 degrees. In full winter, use a temperature of 55-60 degrees. The room thermostat will take care of the rest, as there is no thermal inertia in this type of system; if the radiator turns off, the heating line cools down quickly.
Temperature for Underfloor Heating
Underfloor heating has different constraints, needing operating temperatures lower than 38 degrees. In this type of heating, two degrees can make a difference. If you find yourself at a supply temperature of 28 degrees and the apartment is not warming up enough, raise the temperature to 30 degrees in the boiler.
Usually, two degrees are enough to solve this problem, but it is necessary to wait at least one day for the system to stabilize.
Note: Scheduled operation is not recommended for underfloor heating; use continuous manual operation instead.
Advanced Thermostats and Self-Regulating Supply Temperature
Nowadays, it's possible to let a new generation thermostat self-regulate the boiler's supply temperature, allowing you to set only the room temperature:
- New generation thermostat autonomously chooses the supply temperature: Thus maximizing savings by reducing thermal inertia
- Regulates your heating week for you: On the first ignitions, the thermostat uses an algorithm to determine how long it takes to increase the house's temperature by one degree. It then chooses the climate curve coefficient based on the insulation quality of the apartment and the heating material.
All this is possible with a boiler that supports the Opentherm protocol and a preferably modulating new generation thermostat.
Here are some models with which you can achieve this advantage:
Climate Curve Management
It is also possible to adjust the boiler's supply temperature through the climate curve. This mechanism, which uses the external probe, allows the boiler to adapt the heating system temperature based on a K coefficient. A K regulation coefficient is chosen, which will regulate the temperature of the radiators based on the external temperature (detected by the external probe).
With the system regulated in this way, as the external temperature decreases, the temperature of the radiator system will automatically increase.
Main Issues with the Climate Curve
It is a mechanism not without its issues:
- Difficult to adjust and discourages those who want more frequent adjustments: The climate curve requires entering the parameters of the remote control or the boiler for modification, which is not suitable for everyone. It also requires experience in reading the adjustment graph.
- The external probe is not without problems: If positioned in the shade or in the sun, the external probe can cause several issues.