CE1P2522E / 30.03.2000
Basic Documentation RVL470
Siemens Building Technologies
26/68
Function block "Space heating"
Landis & Staefa Division
8.6.2.1. Settings with the bar
25
22Z
1
1
8.6.2.2. Settings on operating lines
The settings are made on operating lines 14 and 15:
Line
Setpoint
14
TV1, flow temperature setpoint at an outside temperature of +15 °C
15
TV2, flow temperature setpoint at an outside temperature of –5 °C
8.6.2.3. Selection of setting
The kind of setting can be selected on operating line 73:
Line 73
Bar
Line 14
Line 15
0
Active
Inactive
Inactive
1
Inactive
Active
Active
2
Inactive
Display function only, read-
justment only via LPB
Display function only, read-
justment only via LPB
8.6.3. Deflection
The heat losses of a building are proportional to the difference between room tempera-
ture and outside temperature. By contrast, the heat output of radiators does not in-
crease proportionally when the difference between 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 underfloor heating systems), the heating curve is
practically linear – due to the small flow temperature range – and therefore corresponds
to the characteristic of low temperature heating systems.
The slope s is determined according to the following formula:
T
Vw(–5)
−
T
Vw(+15)
s [–] = ––––––––––––––
20 K
where:
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
On the controller, the heating curve is set as a straight line, but the straight line corre-
sponds exactly to the deflected heating curve, because a non-linear outside tempera-
ture scale corresponds to the deflection.
The heating curve is valid for a room temperature setpoint of 20 °C.
