Mixing Valve Control - Siemens LMS14 User Manual

Mixing valve boost
Actuator type
Switching differential
2-pos
Building Technologies Division

6.5.31 Mixing valve control

Line no.
HC1 HC2 HC3
830 1130 1430
To ensure proper flow temperature control via the mixing valve, the current flow
temperature must be higher than the flow temperature setpoint demanded for the
mixing valve. The value set here is added to the heat request.
Note!
If, in addition to mixing heating circuits, pump heating circuits are connected, the
pump heating circuits compensate the increased common flow temperature via the
Overtemperature protection function, and the heating circuit pump cycles accordingly.
Line no.
HC1 HC2 HC3
832 1132 1432
The selection of the type of actuator determines the control behavior of the mixing valve
actuator used.
The controller supports both 2-position and 3-position actuators.
2-position
The controller drives the actuator via one relay output. When the output delivers a
signal, the valve opens. If there is no signal, the valve closes automatically (thermally or
mechanically).
Note!
Control is accomplished with a 2-position controller having an adjustable switching
differential. If the flow temperature lies more than half the switching differential below
the setpoint, relay Mixing valve opening is energized and remains energized until the
flow temperature exceeds the setpoint by half the switching differential.
3-position
The controller drives the actuator via 2 relay outputs. One of the outputs is used for
opening the valve and one for closing it. If none of the relays is energized, the actuator
maintains its position.
Note!
Control is accomplished with a PID controller, whereby the mixing valve's P-band
(Xp) and integral action time (Tn) can be adjusted. The actuator running time can
also be set. The controller's neutral zone is ±1 K. In the case of difficult controlled
systems, the control parameters can be matched to the system.
Line no.
HC1 HC2 HC3
833 1133 1433
With 2-position actuators, the 2-position switching differential must be adapted also.
This is not required with 3-position actuators.
User Manual LMS14...
6 The settings in detail
Operating line
Mixing valve boost
Operating line
Actuator type
2-position
3-position
Operating line
Switching differential 2-pos
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CC1U7471en
07.05.2014