choosing the power for floor heating

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Choosing the correct performance for floor heating is not only about achieving room temperature, but primarily about ensuring stable and economical operation of the entire system. Any mismatch between the hydraulic resistance of the pipe and the flow through the valve leads to temperature instability, excessive noise, or unnecessarily high energy costs.

Heat output calculation and hydraulic resistance

The basis of proper dimensioning is an accurate calculation of the building's heat loss, which determines the required output per square meter. Equally important is estimating the hydraulic resistance of the circuit. In longer floor heating layouts, resistance increases exponentially, requiring a valve with higher flow capacity (higher Kvs) to prevent the flow of water from being "choked."

In practice, we often see situations where technicians install standard valves in long circuits, causing the pump to run at maximum speed and consume more electricity than necessary. Proper setting of the Kvs value ensures that the valve will regulate the flow smoothly even at small temperature differences, without causing vibration or inefficiency.

Deciding on the Kvs value for the valve

The Kvs value expresses the amount of water in m³/h that passes through the valve at a pressure drop of 1 bar when fully open, and is a key parameter for selecting the correct model. For standard apartment floor heating, smaller valves are sufficient, while for industrial buildings or long circuits, models with higher flow capacity are essential, such as EUROMIX F4 5/4" kvs=10,6.

Incorrect selection leads to two extremes: if Kvs is too low, the valve becomes a "bottleneck" and the system will not be able to deliver enough heat; conversely, an overly large valve can cause unstable regulation at low temperatures, as even a small movement of the valve disc will change the flow too drastically.

KVS 6 (e.g., EUROMIX F4 3/4"): Ideal for short circuits up to 80 meters and apartment buildings.
KVS 10 (e.g., EUROMIX F4 1"): Suitable for family homes with medium-length circuits and higher heat losses.
KVS 10,6 and higher: Essential for large commercial spaces and long layouts with high hydraulic resistance.

The role of mixing valves in the system

Mixing valves serve not only to regulate temperature, but also to maintain a constant flow in the boiler circuit, which is critical for the boiler's lifespan and system efficiency. When selecting, we must consider not only the flow capacity, but also the type of connection, whether it is a 2-way or 3-way valve, which will affect the dynamics of the entire system.

A good example of a robust solution for larger applications is the valve ROTODIVERT DN25, which offers high reliability and precise regulation at higher pressures, often needed in systems with multiple individual circuits.

The impact of the actuator on the control characteristics

The valve alone is not enough if it is not properly controlled; the strength and type of actuator must correspond to the torque required by the valve to overcome the water pressure. A too weak actuator cannot fully close or open the valve, leading to leakage and energy loss, while a too strong one can damage the seals due to prolonged stress.

Since floor heating operates at lower temperatures and pressures than radiator systems, an actuator with lower torque but precise position control is often suitable. For detailed information on what actuator size is appropriate for your specific valve, we recommend reading the article on selecting an actuator for radiators.

Practical examples from installation practice

A common mistake during renovations is replacing original valves with new ones without a thorough recalculation of resistance, which leads to the system not functioning as expected. For example, in the installation of a long circuit in a new building, we used ROTODIVERT DN20 instead of a smaller version, because the hydraulic resistance exceeded 2 bars, which would otherwise have prevented the valve from opening even 50%.

On the other hand, in a small apartment unit, we had a problem with vibrations due to the use of an overly large valve, which could not be finely regulated. After replacing it with a model with a lower Kvs value, the system stabilized and the room temperature is maintained with an accuracy of ±0.5 °C, which is key to user comfort.

Hydraulic balancing and temperature difference

When selecting the capacity, it is key to monitor not only the total flow, but also the temperature difference (Δt) between the supply and return; too small a temperature difference forces the pump to operate at a higher capacity, which increases electricity consumption without improving thermal comfort.

Impact of distributor distance on pressure loss

The further the distributor is from the heat source or the longer the pipes leading to individual circuits, the greater the need to compensate for hydraulic resistance, which often requires a valve with a higher Kvs or an additional pump in the circuit.

Common questions

How do I calculate the correct Kvs value for my circuit?

You calculate the required Kvs value by dividing the required flow (m³/h) by the square root of the pressure drop (bar) at the valve, taking into account the resistance of other components in the circuit as well.

Can I use the same valve for radiators and floor heating?

Technically it is possible, but it is not advisable, as floor heating requires a different control range and lower temperatures, which can lead to unstable operation of radiator valves.

Why does the valve get stuck and how can I free it?

Sticking is often caused by lime scale deposits or corrosion, which can be removed by mechanical cleaning or using special solvents, but regular maintenance is the best prevention.

Conclusion

Investing in correctly dimensioned valves and actuators pays off in the form of lower operating costs and a longer lifespan of the entire heating system. Do not underestimate the hydraulic calculation, as the correct performance is the guarantee of comfort and stability in your home.

Do you have a question about this topic?

Having trouble deciding or dealing with a specific situation in your home? Write to us - we are happy to help.