23
ABB i-bus
®
EIB / KNX
Application and planning
The Fan Coil Controller regulates valves with a linear valve characteristic.
The valve position is linearly adjusted to the control value. At a control value
of 0 %, the valve is closed (i.e. likewise 0 %). At a control value of 100 %,
the valve is fully opened (i.e. likewise 100 %). The same ratio applies for all
intermediate values (see Fig. 15).
Fig. 15: Linear valve characteristic
This valve characteristic can be adapted for different valve types.
Many valves have for example almost no flow when they are slightly opened
and already reach their maximum flow rate at 60 – 80 %. There is also the
fact that a disruptive whistling noise is generated in many valves with a low
flow rate.
These effects can be taken into account by limiting the active valve opening
range (see Fig. 16). The positioning frequency of the valve drive can also be
reduced by this restriction.
Fig. 16: Limitation of the active valve opening range
3.5.2 Valve
characteristics
Valve position
Valve control
value
0 %
100 %
0 %
100 %
0 %
100 %
Valve position
Valve control
value
0 %
100 %
Active
valve
opening
range
30%
80%
