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Siemens Building Technologies Basic Documentation RVD230 CE1P2383en
HVAC Products 19 Function block Valve actuator d.h.w. 27.05.2004
19 Function block Valve actuator d.h.w.
19.1 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
19.2 Mode of operation
This function block provides d.h.w. temperature control with a mixing valve, 2-port valve
or diverting valve. The sensor and the type of actuating device required depend on the
type of plant:
Plant type Sensor for con-
trolled variable
Regulating unit
1–3 B72*
0–x, 1–4, 1–8, 1–9,
1–10, 5–4, 5–9, 5–10
B3
2-port valve Y5 in the primary return of
the d.h.w. heat exchanger
2–11 B1
2–12 B1**
2-port valve Y1 in the primary return
(diverting valve Q3 is controlled by the
demand for d.h.w.)
6–2, 6–7 B3
2–2, 2–7 B3
3–2, 3–7, 7–2 B3
Mixing valve Y5 in the intermediate
circuit
* With no maximum limitation of the return temperature, 2-position control is used
** Same function as with d.h.w. heating using 2 flow sensors, e.g. plant types 2–7, 6–7
With the plant types using a diverting valve (2–11 and 2–12), the opening and the clos-
ing time are to be set on operating lines 111 and 112. The setting impacts passing on
of the heat demand signal to the heat exchanger.
19.3 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 30…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 B72 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.
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