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Siemens Building Technologies
HVAC Products
14
Function block Valve actuator heating
circuit
14.1
Operating lines
Line
Function, parameter
91
Running time actuator, heat exchanger heating circuit
92
P-band of heat exchanger control heating circuit
93
Integral action time of heat exchanger control heating circuit
94
Setpoint boost heat exchanger heating circuit
95
Maximum limitation of flow temperature
96
Minimum limitation of flow temperature
14.2
Mode of operation
This function block controls the secondary flow temperature of the heating circuits
equipped with a mixing valve. Depending on the type of plant, this is:
Plant type
Impact on heating circuit 1
All 1–x
Control of valve Y1 according to
sensor B1
2–0, 2–1, 2–6 No valve present
2–2, all 4–x
No valve present
All 3–x
Control of valve Y5 according to
sensor B12
The function block also provides minimum and maximum limitation of the flow tempera-
ture in the controlled heating circuit.
14.3
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.
14.4
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).
Setting the maximum limit value activates the protection against overtemperatures (also
refer to subsection 12.11.3 "Shutdown of pump"
Maximum limitation is not a safety function; for that purpose, a thermostat, thermal re-
set limit thermostat or similar must be used.
Basic documentation RVD240
14 Function block Valve actuator heating circuit
Unit
Factory
setting
s
120
K
35
s
120
K
10
°C
---
Variable...140
°C
---
8...variable
Impact on heating circuit 2
Control of valve Y7 according to
sensor B12
Control of valve Y5 according to
sensor B12
Control of valve Y7 according to
sensor B12
Control of valve Y7 according to
sensor B3
Range
10...873
1...100
10...873
0...50
CE1P2384en
27.05.2004
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