Viessmann VITOCAL 250-A - Automatic Summer;Wintertime Changeover

60
896.0 Correction for outside temperature
To compensate for systematic measuring faults, a cor-
rection value (offset) can be set for the outside temper-
ature sensor.
The correction value can be positive or negative. The
correction value is added to the current outside tem-
perature measurement.
912 Automatic summer/wintertime changeover
912.0 Summer/wintertime changeover
Value Meaning
0 Automatic summer/wintertime changeover
enabled
1 No automatic summer/wintertime changeover
919 Outside temperature damping factor
919.0 Outside temperature damping factor
Time constant for calculating the adjusted outside tem-
perature (low pass filter)
This outside temperature is used for:
■
Calculating the set flow temperature for room heating
■
Switching room cooling on/off
Note
In order to achieve a system response within the inten-
ded time window, outside temperature values with non
adjustable damping are used for other functions (e.g.
the frost protection function).
The continuous averaging of actual temperatures
reduces the influence of brief temperature fluctuations.
The mathematical method applied acts like an attenua-
tion. With this attenuation, the adjusted outside tem-
perature achieves the following values after a sudden
temperature change:
■
63 % of the change after a single averaging interval
■
95 % of the change after three averaging intervals
t
ϑ
AB AB
100%
63%
37%
Fig. 20
A
Time of the sudden temperature change
B
Expiry of one averaging interval
In practical use, this characteristic results not only in
an adjustment but also a delay in capturing the outside
temperature.
t
ϑ
B
A
Fig. 21
A
Outside temperature (not adjusted)
B
Adjusted outside temperature
General parameter group
896 Outside temperature
6218234
Parameter