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Siemens
Basic Documentation RVP360
CE1P2546en
Building Technologies
9 Function block: Space heating
2017-07-24
9.6.3 Deflection
The heat losses of buildings are proportional to the difference of room temperature
and outside temperature. By contrast, the heat output of radiators does not in-
crease proportionally when the difference of radiator and room temperature in-
creases. For this reason, the radiators' heat exchanger characteristic is deflected.
The heating curve's deflection takes these properties into consideration.
In the range of small slopes (e.g. with floor heating systems), the heating curve is
practically linear – due to the small flow temperature range – and therefore corre-
sponds to the characteristic of low temperature heating systems.
Slope ”s” is calculated according to the following formula:
T
Vw( 5)
T
Vw(+15)
s = —————————
20 K
s
Heating curve slope
T
Vw( 5)
Flow temperature setpoint at an outside temperature of 5 °C
T
Vw(+15)
Flow temperature setpoint at an outside temperature of 15 °C
The heating curve is valid for a room temperature setpoint of 20 °C.
9.6.4 Parallel displacement of heating curve
The heating curve can be shifted parallel, manually with the knob for room temper-
ature readjustments. This readjustment is made by the end-user and covers
a range of 4.5...+4.5 °C room temperature.
The parallel displacement of the heating curve is calculated as follows:
Parallel displacement T
Flow
= ( T
Knob
)
*
( 1 + s )
20
10
0
-10
-20
-30
90
80
70
60
50
40
30
2
5
22
D
1
0
100
0
10
10
0
30
T
Rw
T
A
T
V
Parallel displacement of heating curve
s
Slope
T
A
Outside temperature
T
V
Flow temperature
T
Rw
Room temperature setpoint
