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Siemens Heating and D.h.w. Controller RVL481 CE1P2541en
Building Technologies 20 Function block "3-position actuator for d.h.w." 20.05.2008
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 Factory setting (range) Unit
132 Flow temperature boost mixing valve / heat exchanger 10 (0…50) °C
133 Actuator opening time 120 (10…873) s
134 Actuator closing time 120 (10…873) s
135 P-band of control (Xp) 32.0 (1…100) °C
136 Integral action time of control (Tn) 120 (10…873) s
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 precontroller / heat source, the value of operating
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 precontroller / heat source, the value of operating
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 modu-
lating 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.
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