4380397M_MSW_GFX4-GFXTERMO4_08-2018_ENG
PID HEAT/COOL CONTROL
The controller can manage a heating output and a cooling output in a completely independent manner. Heating and
cooling parameters are described below. Parameters for PID (proportional band, integral and derivative time) control are typi-
cally calculated by means of Autotuning and Selftuning functions.
Proportional action:
action in which contribution to output is proportional to deviation at input (deviation = difference between controlled variable
and setpoint
Derivative action:
action in which contribution to output is proportional to rate of variation input deviation.
Integral action:
action in which contribution to output is proportional to integral of time of input deviation.
Control actions
Increasing the proportional band reduces oscillation but increases deviation.
Reducing the proportional band reduces deviation but causes oscillation of the controlled variable (excessively low
proportional band values make the system unstable).
An increase in Derivative Action corresponds to an increase in Derivative Time, reduces deviation, and prevents
oscillation up to a critical Derivative Time value, beyond which deviation increases and there are prolonged oscillations.
An increase in Integral Action corresponds to a decrease in Integral Time, tends to annul deviation between the
controlled variable and the setpoint at rated operating speed.
If the Integral Time value is too long (weak Integral Action), there may be persistent deviation between the controlled variable
and the setpoint.
For more information on control actions, contact GEFRAN.
Proportional, derivative, and integral action
CONTROLS
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