ABB i-bus KNX Product Manual page 31


ABB i-bus KNX
Commissioning
Control value is received as
Options:
This parameter defines how the sent control value is received by the thermostat. Depending on the
selection made, the communication object for the

1 bit: The control value is sent by the thermostat as a PWM signal or a two-step signal (ON/OFF). The
parameter for setting the PWM-cycle time and the communication object Control value, switch 1 bit
appear.
Note
Pulse width modulation
With pulse width modulation, the valve is operated as with 2-point control exclusively in the positions
fully opened and fully closed. In contrast to a 2-point control, the position is not controlled via limit
values, but rather by calculated control values similar to continuous control.
The control value is fixed for a timed cycle and recalculated for the switch on duration of the output. The
control value 20 % at a cycle time of 15 minutes, for example, will be recalculated for a switch on
duration of three minutes.
The control value 50 % results in a switch on duration of 7.5 minutes.
Using pulse width modulation, a relatively exact control of the temperature is achieved without high
levels of overshoot. Simple, attractively-priced thermoelectric valve drives can be used.
Control value
in % [0...100]
Options: 0...100
This parameter determines the control of the output after bus voltage recovery in %.
If a control value is received via a 1 bit value, on parameter
page 30, a value must be entered. This value is used as the basis for calculation of the output
control at bus voltage recovery in %
Note
Control value in %
The actual valve setting in % may diverge from the set value for control in % depending on the
ambient conditions, e.g. room temperature, valve drive used, water pressure in the
heating/cooling system, valve, etc.
The set value in the parameter Control value in % is based on the parameter Cycle time of
PWM. The output is controlled accordingly depending on the setting.
Example parameter settings:
Control value in % [0...100]:
Cycle time of the PWM in s [10...6,000]
With these settings, the output switches ON for 42 s and OFF for 18 s (60 s x 0.7 = 42 s).
Quick heat up/cool down
An additional time is determined that is dependent on the change in the control value and the
closing and opening times of the valve drive. This additional time extends the switch on and off
duration after a change in the control value. Accordingly, the new control value is achieved
quickly.
1 bit
1 byte
*PWM = pulse width modulation.
Cycle time of PWM in s
70 %
60 s
Control value, page 43, (1 bit or 1 byte) is displayed.
VAA/S x.230.2.1 | 2CDC 508 101 D0201 29
[10...6,000],