ABB i-bus
®
KNX
Commissioning
FCA/S 1.x.x.1 | 2CDC508134D0202 99
Valve is
This parameter determines whether the valve is defined as a heating valve or cooling valve.
In the option 2 control values/2 valves (with or without switching object), one valve must be
parameterized as a heating valve and the other as a cooling valve, according to the installation
conditions.
Control value is received as
This parameter defines how the sent control value is received by the room thermostat. Depending
on the selection, the communication object for the Control value, p. 211, (1-bit or 1-byte) is
displayed.
1-bit: The control value is sent by the room thermostat as a PWM signal or a two-step signal
(ON/OFF). The parameter for setting the PWM cycle time is displayed (PWM = pulse width
modulation).
The following message appears:
Set cycle time PWM, open/closing time
for contr. value of valve drive in %
At recovery, controller fault,
forced oper. and characteristic curve
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 the calculated control value, 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 thermoelectric valve drives can be used.
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