Siemens AVS75.39 Series User Manual page 75

Frost protection
CC pump
Control of mixing valve
Mixing valve decrease
Actuator type
Switching differential 2-
pos
Actuator: running time
Mixing valve Xp
Mixing valve Tn
Siemens
Building Technologies
Line no. Operating line
937 Frost prot plant CC pump
Off ¦ On
Under the setting "On", the corresponding CC pump is operated for active plant
frost protection.
Line no. Operating line
938 Mixing valve decrease
939 Actuator type
2-position ¦ 3-position
940 Switching differential 2-pos
941 Actuator running time
942 Mixing valve Xp
943 Mixing valve Tn
945 Mixing valve in heating mode
Control ¦ Open
The refrigeration request from the mixing circuit to the producer is reduced by the
set value. The purpose of this reduction is to enable the mixing valve controller to
compensate for the temperature variations produced by the refrigeration source (2-
position control).
2-position
The controller uses only one relay output to drive the actuator. When the output
delivers a signal, the connected valve opens. When there is no signal, the valve
closes automatically.
3-position
The controller drives the actuator with 2 relay outputs. One output is used for
opening the connected valve, the other for closing it.
For the 2-position actuator, the 2-position switching differential must also be
adapted. The switching differential has no impact on 3-position actuators.
For the 3-position actuator, the running time of the mixing valve actuator can be
adjusted. The actuator running time has no impact on 2-position actuators.
By setting the right proportional band Xp for the mixing valves actuator, the control
behavior of the actuator is matched to those of the plant (controlled system).
The proportional band Xp influences the controller's P-action.
The P band Xp is the range by which the input variable x (controlled variable) must
change to adjust the output variable y (manipulated variable) throughout the entire
positioning range. The smaller the value the greater the jump. The illustration
depicts the reciprocal value 1/Xp = Kp.
By setting the right integral action time Tn, the control action of the mixing valve's
actuator is matched to the behavior of the plant (controlled system).
Tn influences the controller's I-response.
It is the required of the I-portion to undertake the same manipulated variable
change at the given input signal (controlled variable), as immediately provided by
the P-portion. The smaller the Tn the larger/faster the slope.
User manual RVS43.345
The settings in detail
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CE1U2354en_021
2013-09-02