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Building Technologies
Modular Heating Controller RMH760B
CE1P3133en
HVAC Products
9 Heating circuit control
05.02.2007
With a radiator exponent 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. At lower or
higher setpoints, the heating curve is appropriately displaced (also refer to subsection
9.5.3 “Influences on the flow temperature setpoint”).
Outside temperature at a 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
D34
38 °C
32 °C
"20/20 °C"
The lift at the point of inflection is dependent on the flow temperature setpoint and 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 1
(or
2
or
3
)
> Heating curve
Operating line
Range
Factory setting
[Curvepoint 1] outside temp
–50…10 °C
–11 °C
[Curvepoint 1] flow temp
25…140 °C
60 °C
[Curvepoint 2] outside temp
5…30 °C
15 °C
[Curvepoint 2] flow temp
5…140 °C
30 °C
Radiator exponent
1.00…2.00
1.30
•
The heating curve is identical to that of the DESIGO system
•
Setting of the radiator exponent can be derived from the type of heating system and
is based on physical ground
9.5.3
Influences on the flow temperature setpoint
The basis used for the flow temperature setpoint is the heating curve. In addition, the
setpoint is influenced by the following variables:
•
Room temperature setpoints
Inflection point
Note
Example
Rule of thumb:
Example above:
Heating curve
Notes
