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Siemens Heating and D.h.w. Controller RVL481 CE1P2541en
Building Technologies 13 Function block "Setpoint of return temperature limitation" 20.05.2008
13 Function block "Setpoint of return
temperature limitation"
On the function block "Setpoint of return temperature limitation”, the setpoint of mini-
mum limitation of the return temperature or the constant value for shifting maximum
limitation of the return temperature can be adjusted.
13.1 Operating line
Line Function, parameter Factory setting (range) Unit
101 Setpoint of return temperature limitation – Constant value --- (--- / 0…140) °C
13.2 Description
On operating line 101, the setpoint of minimum limitation of the return temperature or the
constant value for shifting maximum limitation of the return temperature can be adjusted.
When entering ---, the function is deactivated, which means that the return temperature
will not be limited.
For more detailed information about the maximum limitation of the return temperature,
refer to chapter “14 Function block "District heat".
If the settings of this function block have been locked (contact H3, or on operating line
248; refer to the respective sections), the display shows
when pressing buttons
and .
13.3 Minimum limitation of the return temperature
This function block ensures minimum limitation of the boiler return temperature where
possible or required. This applies to the following plant types:
• Plant type 1–x, Heating circuit control with mixing group
• Plant type 4–x, Precontrol with mixing group
• Plant type 5–x, Precontrol with boiler
Minimum limitation of the return temperature prevents boiler corrosion due to flue gas
condensation.
13.3.1 Acquisition of measured values
A temperature sensor with a sensing element LG-Ni 1000 is required in the return. With
plant type 1–x, the return temperature can also be delivered via LPB. In interconnected
plants, only one return temperature sensor per segment may be used.
13.3.2 Mode of operation
If the return temperature falls below the set minimum limit value, the temperature differ-
ential between minimum limit value and actual value will be integrated. From this, a
critical locking signal will be generated and transmitted to the connected loads. This
causes the loads to reduce their setpoints, thus consuming less energy.
If the return temperature returns to a level above the minimum limit, the integral will be
reduced, resulting in a reduction of the critical locking signal. The connected loads rise
their setpoint values.
When the integral reaches the value of zero, the minimum return temperature limitation
will be deactivated, in which case the critical locking signal is zero.
If minimum limitation of the return temperature is active, the display shows
.
Minimum limitation of the return temperature can be deactivated.
Section “25.4.7 Gain of locking signal” provides information on which the critical locking
signal is sent to and how the consumers respond to it.
The minimum limit value is to be set on operating line 101. Setting --- = (inactive)
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