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Siemens Building Technologies
HVAC Products
18
Function block Valve actuator d.h.w.
18.1
Operating lines
Line
Function, parameter
111
Opening time actuator of d.h.w. circuit
112
Closing time actuator of d.h.w. circuit
113
P-band of d.h.w. control
114
Integral action time of d.h.w. control
115
Derivative action time of d.h.w. control
116
Setpoint boost d.h.w. charging
117
Maximum setpoint of d.h.w. temperature
118
Setpoint boost mixing valve / heat exchanger d.h.w.
119
Reduced d.h.w. setpoint for storage tank sensor at the bottom
120
Circulating pump for d.h.w. charging
124
Load limit for actuation of flow switch
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
1–3
B71
Valve Y5
2–2
B3
Mixing valve Y5
1–4, 1–8,
B3
Valve Y5
1–9, 4–x
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.
Basic documentation RVD240
18 Function block Valve actuator d.h.w.
Unit
s
s
K
s
s
K
°C
K
K
%
Location of sensor and regulating unit
Primary return of d.h.w. heat exchanger
D.h.w. flow (intermediate circuit)
Factory
Range
setting
35
10...873
35
10...873
35.0
1.0...100.0
35
10...873
16
0...255
16
0...50
65
20...95
10
0...50
5
0...20
0
0 / 1
25
0...60
CE1P2384en
27.05.2004
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