165/232
Building Technologies
Boiler sequence controller RMK770
CE1P3132en
HVAC Products
10 Heating circuit control
23.04.2009
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
A
at curvepoint
c
.
This means that curvepoint
d
(usually set at the heating limit) does
not
directly deter-
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
A
= –10 °C
30% of that range = 9 K
Hence, the inflection point is at an outside temperature of 11 °C.
nH = 1.5
nH = 1.0
30 K = 100 %
9 K = 30 %
-10
-5
0
5
10
15
20
25
60
50
40
30
20
10
0
TFl
TO
3131
D
34
38 °C
32 °C
"20/20 °C"
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
at nH = 1
– 20 °C) × (nH – 1)
Lift
≈
(32 °C – 20 °C)
× (1.5 – 1) = 6 K
Main menu > Heating circuit > Heating curve
Operating line
Range
Factory setting
[Curvepoint 1] outside temp
–50…10 °C
–11 °C
[Curvepoint 1] flow temp
30…130 °C
60 °C
[Curvepoint 2] outside temp
5…30 °C
15 °C
[Curvepoint 2] flow temp
30…130 °C
30 °C
Radiator exponent
1.00…1.50 1.30
Main menu > Settings > Heating circuit > Heating curve
Operating line
Range
Factory setting
Radiator exponent
1.00…2.00
1.30
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.
Inflection point
Note
Example
Rule of thumb:
Example above:
Settings
Notes