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Siemens Building Technologies
Basic Documentation RVL471
CE1P2524E
HVAC Products
20 Function block "3-position actuator for d.h.w."
23.10.2002
20 Function block "3-position actuator
for d.h.w."
With plant types x–2 and x–4, this function block provides 3-position control of d.h.w.
heating.
20.1 Operating lines
Line
Function, parameter
Unit
Factory
setting
Range
132
Flow temperature boost mixing valve / heat exchanger
°C
10
0...50
133
Actuator opening time
s
120
10...873
134
Actuator closing time
s
120
10...873
135
P-band of control (Xp)
°C
32.0
1...100
136
Integral action time of control (Tn)
s
120
10...873
20.2 Function
The 3-position controller is used for d.h.w. control (plant types x–2 and x–4).
20.2.1
Flow temperature boost
•
Plant type x–2 (mixing valve):
For the temperature demand to the primary controller / heat source, the value of oper-
ating line 132 is added to the setpoint of d.h.w. flow sensor B3.
•
Plant type x–4 (heat exchanger):
For the temperature demand to the primary controller / heat source, the value of oper-
ating line 132 is added to the setpoint of d.h.w. flow sensor B3.
20.2.2
D.h.w temperature control
The control process depends on the type of plant:
•
Plant type x-2: The control mode is PI; the flow temperature is controlled by the
modulating mixing valve
•
Plant type x-4: The control mode is PID; the flow temperature is controlled by the
modulating 2-port valve
Owing to the I-part of PI control, there is no offset. The opening and closing times of the
actuator can be adjusted separately.
20.3 Pulse lock
If, during a period of time that equals 5 times the running time, the actuator has re-
ceived only closing pulses, additional closing pulses delivered by the controller will be
locked. This minimizes the strain on the actuator.
For safety reasons, the controller delivers a one-minute closing pulse at 10-minute
intervals.
An opening pulse negates the pulse lock.
