Function Block "District Heat; Operating Lines; Limitations; Maximum Limitation Of The Primary Return Temperature - Siemens RVL481 Basic Documentation

Purpose
Note
Generation of the
maximum limit value
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Siemens
Building Technologies
14

Function block "District heat"

Together with function block "3-position actuator heating circuit", this function block
provides flow temperature control in plants with an indirect (heat exchanger) or direct
district heat connection.
Depending on the type of plant, if acts as a
• flow temperature controller for weather-compensated control of space heating with a
district heat connection (plant type 3–x)
• precontroller for demand-compensated control of a main flow (plant type 6–x)
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
and .
14.1

Operating lines

Line Function, parameter
112 Slope of maximum limitation of return temperature
113 Start of shifting limitation of maximum limitation of return tem-
perature
114 Integral action time of maximum limitation of return temperature
115 Maximum limitation of return temperature differential
116 Minimum stroke limitation (Ymin function)
14.2

Limitations

14.2.1 Maximum limitation of the primary return temperature

The primary return temperature uses maximum limitation to
• make certain that too hot water will not be fed back to the district heating network
• minimize piping losses of the district heating utility
• comply with the regulations of the utility
The maximum limitation of the primary return temperature is inactive upon d.h.w re-
quest via data bus.
The maximum limit value is generated from the following variables:
• Constant value (setting on operating line 101)
• Slope (setting on operating line 112)
• Start of compensation (setting on operating line 113)
The current limit value can be determined as follows:
• If the outside temperature is higher than or equal to the value set for the start of com-
pensation (setting on operating line 113), the current limit value is the constant value
entered on operating line 101
• If the outside temperature is lower than the value set for the start of compensation, the
current limit value is calculated according to the following formula:
T = T + [(T
L L constant L start
Heating and D.h.w. Controller RVL481
14 Function block "District heat"
– T ) × s] [°C]
A
when pressing buttons
Factory setting (range) Unit
0.7 (0.0...40)
10 ( − 50...+50)
°C
30 (0...60) min
--.- (--.- / 0,5...50) °C
6 (-- / 1...20) min
CE1P2541en
20.05.2008