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Heating Control via KNX
UFH is becoming the most popular heating source when constructing new builds, as it is proven to be one of the most comfortable and efficient heating systems. In order to achieve maximum comfort and get the most from your system, the right control should be put in place and this can be achieved in a simple way with KNX.
Hydronic UFH
With hydronic, hot water passes through pipes and transfers heat up into the room, with the level of heat being dependent on the depth of the pipes. In order to maintain an even distribution of heat, the pipes should be run in a coil, as shown below.
Depending on the size of the floor, it is not uncommon for a room to have more than one coil. For example, a large open-plan living and dining area may require two coils. Similarly, two small rooms together such as an en-suite shower room and a walk-in wardrobe can be heated by just one coil.
Each coil is connected to a manifold and each zone on the manifold is controlled with an electro-thermal actuator. This is then connected to a KNX manifold controller.
Depending on the controller chosen, there is often the option to connect two zones to one channel. This is particularly useful when two coils are needed for a larger room.
Considerations when controlling UFH
There are three considerations to make when controlling under-floor heating:
1) Maintained Air Temperature
The most common way to control underfloor heating maintained air temperature takes its demand for each room from the KNX thermostat.
2) Maintained Floor Temperature
Often used in bathrooms and other tiled areas, this ensures a minimum comfort temperature at all times. To achieve this, a floor probe is required, either used as an input on the room controller with a weighting in favour of the floor, or as a separate control loop.
3) Over Temperature Cut Off
This is used with electric UFH or as a safety mechanism for certain floor types such as delicate wood finishes. The simplest way to achieve this is to install a floor probe with a separate thermostat. This gives clear definition between the standard thermostat and the ‘over temperature’ override.
