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Siemens Building Technologies
Basic documentation RVD240
CE1P2384en
HVAC Products
18 Function block Valve actuator d.h.w.
27.05.2004
18
Function block Valve actuator d.h.w.
18.1 Operating
lines
Line
Function, parameter
Unit
Factory
setting
Range
111
Opening time actuator of d.h.w. circuit
s
35
10...873
112
Closing time actuator of d.h.w. circuit
s
35
10...873
113
P-band of d.h.w. control
K
35.0
1.0...100.0
114
Integral action time of d.h.w. control
s
35
10...873
115
Derivative action time of d.h.w. control
s
16
0...255
116
Setpoint boost d.h.w. charging
K
16
0...50
117
Maximum setpoint of d.h.w. temperature
°C
65
20...95
118
Setpoint boost mixing valve / heat exchanger d.h.w.
K
10
0...50
119
Reduced d.h.w. setpoint for storage tank sensor at the bottom
K
5
0...20
120
Circulating pump for d.h.w. charging
0
0 / 1
124
Load limit for actuation of flow switch
%
25
0...60
18.2 Mode
of
operation
This function block provides d.h.w. temperature control with a mixing valve or 2-port
valve. The sensor and the type of actuating device required depend on the type of
plant:
Plant type Sensor Regulating unit
Location of sensor and regulating unit
1–3
B71
Valve Y5
Primary return of d.h.w. heat exchanger
2–2 B3
Mixing
valve
Y5
1–4, 1–8,
1–9, 4–x
B3 Valve
Y5 D.h.w. flow (intermediate circuit)
18.3 Control
process
If the flow temperature deviates from the setpoint, the 2-port or mixing valve is adjusted
in a stepwise fashion to compensate for the deviation (with plant type 1–3, this can also
be accomplished with 2-position control). The controller drives an electric or electrohy-
draulic actuator.
The ideal running time of the actuator is 10...35 seconds.
The actuator’s opening and closing times are separately adjustable, thus making cer-
tain that actuators with asymmetric running times can also be used.
To enhance the control performance, the derivative action time (D-part of PID control)
can be adjusted, in addition to the P-band and the integral action time.
If, with plant type 1–3, no return sensor B71 is used, the function block will operate as a
2-position controller. When there is a demand for heat, 2-port valve Y5 will be fully
opened; with no demand for heat, it is fully closed. This takes place independent of
whether or not maximum limitation of the d.h.w. return temperature is activated.
18.4 Setpoint
boost
Setpoint boost ensures that the flow temperature required by the consumer to perform
its function (control) will be delivered by the heat source.
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