Siemens AVS75.39 Series User Manual page 89

Control of mixing valve
Mixing valve boost
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
2130 Mixing valve boost
2131 Mixing valve decrease
2132 Actuator type
2-position ¦ 3-position
2133 Switching differential 2-pos
2134 Actuator running time
2135 Mixing valve Xp
2136 Mixing valve Tn
To ensure adequate mixing, the actual value of the boiler flow temperature must be
higher than the required setpoint of the mixing valve flow temperature, enabling
that temperature to be controlled. The controller generates the boiler temperature
setpoint based on the increase set here and the current flow temperature setpoint.
To ensure adequate mixing in cooling mode, the actual value of the cooling flow
temperature must be lower than the required temperature setpoint of the mixing
valve flow since otherwise that temperature could not be controlled. The controller
generates the refrigeration request based on the decrease set here plus the
current flow temperature setpoint and sends the request to the refrigeration plant.
Selection of the type of actuator determines the way the control action impacts the
type of mixing valve actuator used.
For a 2-position actuator, the 2-position switching differential must also be adapted.
This is not required when using 3-position actuators.
Setting the running time for the actuator used with the mixing valve.
The proportional band Xp influences the controller's P-action.
Xp is the range by which the input signal (control variable) needs to change for the
output signal (manipulated variable) to be adjusted across the whole correcting
span.
The smaller Xp, the greater the change of the manipulated variable.
Tn influences the controller's I-behavior.
Tn is the time required by the I-action with a given input signal (control variable) to
bring about the same change to the manipulated variable as that produced
immediately by the P-action.
The smaller Tn, the steeper/faster the slope.
User manual RVS43.345
The settings in detail
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CE1U2354en_021
2013-09-02