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Siemens Building Technologies
Basic Documentation RVD230
CE1P2383en
HVAC Products
27 Function block DRT and maximum limitation of the return temperature
27.05.2004
27
Function block DRT and maximum
limitation of the return temperature
27.1 Operating
lines
.
Line Function, parameter
Unit
Factory
setting
Range
171 Maximum limitation of primary return temperature heating circuits
0
0 / 1
172 Upper constant value, maximum limitation of the primary return
temperature
°C
70
Variable…140
173 Slope, maximum limitation of the primary return temperature
7
0…40
174 Start of compensation (point of inflection), maximum limitation
of the primary return temperature
°C
10
–50…+50
175 Lower constant value, maximum limitation of the primary return
temperature
°C
50
0…variable
176 Maximum setpoint of the return temperature with d.h.w. heat-
ing
°C
---
--- / 0…140
177 Maximum limitation of the secondary return temperature,
reduction to the primary limit value
°C
---
--- / 0…50
178 Integral action time of the primary return temperature limita-
tions
min
30
0…60
179 Limit value of the maximum limitation of the temperature
differential
K
--.-
--.- / 0.5…50.0
180 Max. setpoint of the return temperature during d.h.w. heating at
the legionella setpoint
°C
---
--- / 0…140
This function block contains all parameters of the district heat network. Since many
district heat utilities demand locking of the settings, they are arranged on the locking
functions level.
The following function blocks also belong to the locking function level. It includes all
operating lines from 171 through 196. This level can only be accessed with a code.
Also refer to subsection 32.1.6 "Setting levels and access rights".
In addition, locking on the hardware side is possible (operating line 196).
27.2 Maximum limitation of the primary return
temperature
27.2.1 General
The primary return temperature uses maximum limitation to
•
ensure that too hot water will not be fed back to the district heat network
•
minimize the pumping power of the district heat utility
•
comply with the regulations of the utility (connection requirements)
Maximum limitation of the return temperature acquires the return temperature on the
primary side and throttles the primary 2-port valve if the limit value is exceeded.
Precontroller and heating circuit
D.h.w. circuit
Plant type
Sensor Regulating
unit Sensor
Regulating
unit
0–x –
–
B72 Y5
1–x, 5–x
B7
Y1
B72
Y5
2–x, 3–x,
6–x, 7–2
B7 Y1 B7
Y1
8–4 B7
Y5
B7 Y5
Maximum limitation acts on both the heating circuit and the d.h.w. circuit; both consum-
ers have their own limit value.
Note