Function40; Maximum Limitation Of The Return Temperature Differential (Drt Limitation); Purpose - Siemens RVL470 Basic Documentation

12.2.2.3. Function

12.2.3. Maximum limitation of the return temperature differential (DRT limitation)

12.2.3.1. Function

12.2.3.2. Purpose

CE1P2522E / 30.03.2000
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T
PR
90
80
70
T
L constant
60
50
40
30
20
30
20
T
A
s Slope of limitation (operating line 112)
T Actual outside temperature
A
T Constant value of limitation (operating line 101)
L constant
T Start of shifting limitation (operating line 113)
L start
T Primary return temperature
PR
The outside temperature is used as a compensating variable for maximum limitation of
the primary return temperature. It can be delivered either by the local sensor or the LPB.
Limitation operates according to the selected characteristic:
•
When the outside temperature falls, the return temperature will initially be limited to
the constant value
•
If the outside temperature continues to fall, it will reach the selected starting point for
shifting compensation. From this point, the limit value will be raised as the outside
temperature falls. The slope of this section of the characteristic can be adjusted
Maximum limitation of the return temperature has priority over maximum limitation of the
flow temperature.
This function can be deactivated on operating line 101.
If the return temperature is limited, the display shows
For the differential of primary return and secondary return temperature, a maximum
limitation can be set. For this purpose, a temperature sensor (sensing element LG-
Ni 1000 Ω at 0 °C) is required in the secondary return.
If the differential of the two return temperatures exceeds the adjusted maximum limit,
the flow temperature setpoint will be reduced.
If maximum limitation of the return temperature differential is activated, the display
shows .
DRT limitation has priority over maximum limitation of the flow temperature.
This function can be deactivated (setting --- on operating line 115).
Limitation of the return temperature differential
•
prevents idle heat resulting from excessive cooling down
•
optimizes the volumetric flow
•
is a dynamic return temperature limitation
•
shaves peak loads
•
ensures the lowest possible return temperatures
Basic Documentation RVL470
Function block "District heat"
s
T
L start
10 0 -10
.
Siemens Building Technologies
Landis & Staefa Division