Cascade Curvature - Viessmann Vitodens 200 Operating Instructions And User's Information Manual

Cascade curvature

Unlike the conventional 1.0 curvature and its linear relationship between outdoor and supply temperature, the
Cascade Control allows a curvature setting to be programmed. This modifies the linear relationship from a
straight line into an arc. The arc runs from the starting (anchor) point to the end point that has been
programmed into the control during set-up.
The arc bows more at the bottom end of the curve and gradually starts tapering back to the Flow Temperature
Climazone Point at the top. Since the points that the curvature operates in can be adjusted, a "bump" in
temperature can be created anywhere along the slope. Each .10 increment adds 1.8ºF / 1ºC to the calculated
supply temperature. This increase is most noticeable in the 41ºF to 23ºF / 5ºC to -5ºC range. The closer the
points are together, the smaller the "bump" is to the point where a 1.6 curvature may increase supply
temperature by only 4ºF / 2ºC.
Sample graph (with 1.1 to 1.6 curvature
The graph below shows the incremental increase of curvatures from 1.1 to 1.6. They finish off with a
combination of all the major curvature settings. Note the gradual increase of temperatures from setting to
setting. Because the increments are in units of 100, the curvature can be quite fine.
°F °C
176 80
158 70
140 60
122 50
104 40
86 30
68 20
50 10
40 35
104 95
40
)
30 25 20 15
86 77 68 59
Outdoor Temperature
10 5 0 -5
50 41 32 23
-10 -15 -20 -25
14 5 -4 -13
-30 °C
-22
°F