Single Room Extension with Self-Acting Control

A return temperature limiter will maintain the return temperature from the UFH at a constant level and secure a constant floor temperature. Since there is a co-relation between the floor surface temperature and the room temperature, the room temperature will be held, more or less, at a constant level.

- Used in systems which are predominately heated by radiators (normal system design temperatures 82/71°C) and where Underfloor Heating represents only a minor part of the system, for example a single room or small extension

- Used in systems where a mixing valve arrangement, used to reduce the flow temperature of water flowing to the underfloor heating (UHF) circuit to a level acceptable for floor heating, is to be avoided because of cost

- Used for UFH systems where it is essential to maintain a constant and comfortable floor surface temperature, for example in bathrooms with ceramic tiled floors

- Also ideal for rooms with high peak of free heat gains, for example conservatories, where a room temperature based control system could result in a cold floor
Suitable for both central conventional and manifold or distribution pipe-work systems

- Ideal where easy installation and operation and long life reliability are essential

- It is only suitable for solid floor constructions and UFH systems where pipes are laid in a counter flow pattern to achieve even floor temperature.

Danfoss produce a range of self-acting controls which are simple to install. The product, which comprises a valve enclosure which is built into a wall or partition, a valve, a facia plate and a sensor, is available in a version which controls return water temperature, type FHV-R, and a version which controls room temperature, type FHV-A. A description of the application areas for both types follows.

FHV-R Return Temperature Controller -
The FHV-R valve utilises an FJVR return temperature limiter sensor which controls the temperature of the water leaving the floor heating circuit. As there is a good correlation between water and floor temperature, the FHV-R solution also ensures a warm floor is maintained. The FHV-R solution is ideal for use in systems operating at normal flow and return temperatures (70-80°C) and provides the perfect solution for areas with high heat gains such as conservatories. A mixing valve is not needed with this type of control.

FHV-A Room Temperature Controller -
The FHV-A utilises an RA2000 thermostatic sensor to control room temperature. The FHV-A solution should be used in systems where the flow temperature is below 50°C.