Rehau STAR 20 Installation Manuallines page 20

Adjustments are made dependent upon:
- Continuous temperature readings from each room controller
- The end user setings such as room temperature set point and
programmed night set-back periods on the timer
ZV
IV
IV
HLS
CP
IV
RT
RT
Figure 3. Individual zone controlwith FH
Constant Temperature (CT) Mixing Options
Compact Mixer Unit
- Only for domestic/light commercial applications
- For outputs up to 12kW use 1/2" valve set (not to be used to size
primary pipes)
- For outputs between 12 - 18kW use 3/4" valve set (not to be used
to size primary pipes)
- The circulating pump only circulates the warm water through the
circuits. A separate main system pump is needed to supply the
manifolds with hot water from the boiler
Ω"or æ"
Ω"or æ"
Figure 4. Compact mixer unit fitted to the right side of the manifold with FH flow header on top, FH return header on bottom.
20
UFH Control centre
UFH - Flow
UFH - Manifold
AC AC AC AC
UFH - Return
Working Principle
The compact mixer regulates the main system fl ow from the boiler
directly into the manifold. It mixes the high temperature water from
the main system fl ow (usually required temperature + 70°C), with
the cooler water from the FH return of the circuits to ensure the right
temperature. The thermostatic inlet valve (TIV) allows small amounts
from the main system fl ow to enter the return header, where it mixes
with the return water from the circuits. The circulating pump (CP)
maintains an uninterrupted fl ow of water from the return header up
into the fl ow header and back into the fl oor circuits as long as there is
a demand signal present from any of the room thermostats.
The temperature of this mixed fl ow is measured by the in-line
temperature probe, which feeds back to the thermostatic head on the
RT
(TIV). The thermostatic head of the thermostatic inlet valve (TIV) is set
to achieve the required design fl ow temperature. Once the required
RT
design fl ow temperature is detected by the in-line temperature probe
it closes the thermostatic inlet valve (TIV), No further main system
fl ow is allowed into the return header, until the measured temperature
falls below the design fl ow temperature. The unit also features a high
temperature limit stat (HLS) which is explained later in the section on
Temperature Safety Options.