57 © STULZ GmbH – all rights reserved EN/06.2019/G57
C7000 INSTRUCTIONS fOR A/C UNITS
Instruction for the setting of a PID controller
This instruction gives an answer to the following questions with the example of a G valve. These measures can
also be used for other components which are controlled by a PID controller:
1.) Why does the G valve react too fast?
2.) Why does the G valve react too slowly?
3.) Why does the G valve oscillate?
1.) PID controller too fast → I factor too big or P factor too big
2.) PID controller too slow → I factor too small or P factor too small
3.) PID controller oscillates → there are resonances between the PID controller and the system
which has to be controlled. This happens mostly if: 1.) the PID cont-
roller is too fast.
PID controller setting:
P factor on 1
I factor on 1
D factor on 0
the setpoint.
Not only the control parameters have an influence on the control characteristics but also, e.g for the G valve,
the actual water temperature and the actual compressor speed.
So it may happen that the G valve tends to oscillate with the default setting, when the water is very cold or the
compressor is running slowly and that the valve reacts a bit too slowly when the water is very warm and the
compressor is running fast.
The default settings for the G valve are chosen in such a way that they work for possibly all operating states in
a satisfying way. Optimizations on one side (control speed) can easily entail a significantly worse behaviour on
the other side (control stability and accuracy).
To Next Page
Loading...
