28/57 CC1B7865en 05.12.2002 HVAC Products
5. Operating modes
When a heating system is switched off for a longer period of time, the actual value will
drop of course.
To achieve a faster control response, the controller immediately starts in high-fire
operation as soon as the control deviation (x-w) drops below a certain limit value. This
limit is calculated as follows:
Limit value = 2 * (HYS1-HYS3)
In that case, response threshold «Q» is inactive, independent of the operating mode
and the controlled variable (temperature or pressure).
Operating mode: Modulating, floating output
HYS1 = -3 K
HYS3 = +5 K
w = 60 °C
Limit value = 2 * (-3 - 5) = 2 * (-8) = -16 K
At an actual value below 44 °C, the heating up procedure immediately starts in high-fire
operation, instead of in the thermostat mode.
7865d20/1099
W
HYS1
HYS3
t
2 x (HYS1 - HYS3)
X
°C
db
5.7 Cold start of the plant
Example
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