Setting the underfloor heating - why this is important

The optimal setting of underfloor heating is fundamental for an energy-saving and effective operation of the underfloor heating. In many cases, it is not the system's design errors, but rather incorrect settings in the system that lead to high energy consumption and poor heating efficiency. Read everything about setting up underfloor heating here.

Important setting values

Some values in the system are determined by the dimensioning of the underfloor heating and should not be changed. Changes require an experienced specialist who knows the heating, or at least has a heating plan and the necessary calculations for dimensioning available.

  • Also read - underfloor health
  • Also read - retrofitting underfloor heating costs
  • Also read - Bleeding underfloor heating

Hydraulic balancing

Every underfloor heating (like radiator heating) requires a so-called hydraulic balancing.

This determines which pressure should prevail in which heating circuit. The pressures in the different heating circuits are not the same. The distribution of the individual pressure values depends on various factors:

  • the required heating power in the respective heating circuit (heating demand!)
  • the volume flows in the individual heating circuits
  • the pipe length in the respective heating circuit
  • the subsurface below the underfloor heating in the respective heating circuit
  • the floor covering and the covering thickness in the respective heating circuit
  • the set flow temperature of the heating

If possible (if not necessary), the set values of the hydraulic balance should not be changed, but rather leave the settings to a heating contractor.

Other important setting values for underfloor heating

Flow temperature

The flow temperature with underfloor heating is significantly lower than with radiator heating. This is because the underfloor heating is radiant heating that emits its heat directly via thermal radiation. Radiator heating, on the other hand, is what is known as convection heating, which is intended to heat the room air.

While the flow temperature for radiator heating must always be above 55 ° C, a flow temperature of a maximum of 35 ° C is normally set for modern underfloor heating systems. In individual cases, it can be chosen to be lower for reasons of economy.

Return temperature

The return temperature is the temperature of the water that runs back from the heating pipes. Changes to the flow temperature always have an effect on the return temperature, and vice versa.

Settings for the return temperature can also be used to control the development of the heating power to a certain extent. Settings should only be changed by a specialist who knows the system and its values.


The spread is the temperature difference between the flow and return temperatures. It is usually given in Kelvin in technical plans and calculations. When specifying temperature differences, however, the values in Kelvin correspond 1: 1 to the values in ° C.

If the flow temperature is 35 ° C and the return temperature 32 ° C then the spread is exactly 3 ° C or 3 K.


The flow is the amount of water that flows through the heating pipes of a particular heating circuit. The term "volume flow " is not always to be equated with this, as it is defined slightly differently from a technical point of view.

The changes in the flow rate change the heat output in individual heating circuits. Basically you can say: the higher the flow, the more power in the respective heating circuit.

The determination of the flow rate for the individual heating circuits is a matter of the so-called "hydraulic balancing". In addition, all other performance values must always be taken into account as they have an influence (flow and return temperature, spread, pipe lengths, etc.)

Attitudes as a layperson

In most cases (if there are no room thermostats) you can only set the room temperature control.

This is done via the adjustment valves for temperature control. On the other hand, it is better to keep your fingers off the hexagon bolts, because they are used for hydraulic balancing. Making changes here haphazardly can be problematic if you don't proceed in a targeted manner.

To test the heater and roughly adjust it, you can proceed as in the instructions below. Then let the heating run through.

However, changes to the flow temperature and the spread should not be made, as these values are a matter of calculation. Only the specialist company can make the correct settings here.

Quick comparison - step by step

  • Underfloor heating
  • Allen wrench in the appropriate size

1.Open all setting controls

Fully open all valves for temperature control. Also fully open all hexagon adjusting screws. Hang a thermometer in each room. Wait two days, always keeping the rooms closed.


Check the temperatures after two days. Slowly close the hexagon head screws for hydraulic balancing in all rooms that are above the target temperature. After a reasonable waiting time (hours to approx. 1 day) check how far the temperature has dropped. The setting should achieve a temperature that is 1 ° C above the target temperature.

3. Regulate room temperature

If the target temperature + 1 ° C has been reached in all rooms, be careful (!) with the temperature regulators until the desired target temperature is reached in each room.

Tips & Tricks Please note: all heating settings are related! Changes in a value may have detrimental changes at a different value, and thus make the heating inefficient or less powerful. If you are not sure, make the settings always make from an experienced heater operation that knows the respective underfloor heating.