Siemens Synco 700 Series Basic Documentation page 165

Inflection point
Note
Example
Rule of thumb:
Example above:
Settings
Notes
Building Technologies
HVAC Products
With a radiator exponent nH between 1...1.5, the heating curve is only slightly deflected
and can therefore be replaced by linearized sections. This is achieved by setting an-
other curvepoint, the so-called inflection point.
The inflection point lies 30% below the outside temperature at which the flow tempera-
ture setpoint is 20 °C and the outside temperature
This means that curvepoint
mine the location of the inflection point.
The basic heating curve applies to a room temperature setpoint of 20 °C. If the setpoint
is lower or higher, the heating curve is appropriately shifted (refer to subsection 10.5.3
"Influence on the flow temperature setpoint").
Outside temperature at the flow temperature setpoint of 20 °C = 20 °C
Outside temperature = –10 °C
A
30% of that range = 9 K
Hence, the inflection point is at an outside temperature of 11 °C.
TFl
60
50
40
30
20
10
0
-10 -5
The lift at the inflection point is dependent on the flow temperature setpoint and on the
radiator exponent.
Rule of thumb for calculating the lift at the inflection point:
≈
Lift (Flow temperature setpoint
≈
Lift (32 °C – 20 °C)
Main menu > Heating circuit > Heating curve
Operating line
[Curvepoint 1] outside temp
[Curvepoint 1] flow temp
[Curvepoint 2] outside temp
[Curvepoint 2] flow temp
Radiator exponent
Main menu > Settings > Heating circuit > Heating curve
Operating line
Radiator exponent
The heating curve is identical to that of DESIGO.
Setting of the radiator exponent can be derived from the type of heating system and is
based on physical ground.
Boiler sequence controller RMK770
10 Heating circuit control
A
(usually set at the heating limit) does not directly deter-
nH = 1.5
nH = 1.0
0 5 10
30 K = 100 %
– 20 °C) × (nH – 1)
at nH = 1
× (1.5 – 1) = 6 K
Range
–50...10 °C
30...130 °C
5...30 °C
30...130 °C
1.00...1.50
Range
1.00...2.00
at curvepoint .
38 °C
"20/20 °C"
32 °C
20
15
9 K = 30 %
Factory setting
–11 °C
60 °C
15 °C
30 °C
1.30
Factory setting
1.30
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23.04.2009