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Siemens Building Technologies Basic Documentation RVD230 CE1P2383en
HVAC Products 15 Function block Valve actuator heating circuit 27.05.2004
15 Function block Valve actuator heat-
ing circuit
15.1 Operating lines
Line Function, parameter Unit Factory
setting
Range
91 Running time actuator, heat exchanger heating circuit s 120 10…873
92 P-band of heat exchanger control heating circuit K 35 1…100
93 Integral action time of heat exchanger control heating circuit s 120 10…873
94 Setpoint boost heat exchanger heating circuit K 10 0…50
95 Maximum limitation of flow temperature °C --- Variable…140
96 Minimum limitation of flow temperature °C --- 8…variable
15.2 Mode of operation
This function block controls the secondary flow temperature of the heat
exchanger.
• Plant types 1–x: In the heating circuit, according to the temperature acquired with flow
sensor B1. The function block controls 2-port valve Y1 in the primary return of the heat-
ing circuit’s heat exchanger
• Plant types 3–x and 7–2: In the heating circuit, according to the temperature acquired
with flow sensor B12. The function block controls the mixing valve in the hating circuit
flow. Depending on the type of plant, this is:
Plant type Control output
3–2, 3–7, 7–2 Y7 / Y8
3–1, 3–6 Y5 / Y6
The function block also provides minimum and maximum limitation of the flow tempera-
ture in the controlled heating circuit.
With plant types 0–x, this function block is inactive; these types of plant are used exclu-
sively for d.h.w. heating.
15.3 Control process
If the actual flow temperature deviates from the setpoint, the mixing valve offsets the
deviation in a stepwise fashion. The controller drives an electric or electrohydraulic
actuator. The ideal running time of the actuator is 2…3 minutes.
The actuator’s running time, the P-band and the integral action time are to be set on
operating lines 91…93, depending on the type of plant. In addition, the heat ex-
changer’s or mixing valve’s setpoint boost can be adjusted.
The setpoint boost also applies to plant type 8–4.
15.4 Maximum limitation of the flow temperature
The maximum limit value is to be set on operating line 95. The setting range for the
maximum limit value lies between the minimum limit value (setting on operating line 96)
and 140 °C.
At the limit value, the heating curve runs horizontally. This means that the flow tem-
perature setpoint cannot exceed the maximum value.
This function can be deactivated (entry of --- on operating line 95).
The setting of the maximum limit value activates the protection against overtempera-
tures (also refer to subsection 12.11.3 "Shutdown of pump").
Maximum limitation of the flow temperature also acts in the case of plant types 8–4.
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