The previous example can be used to illustrate the use of multi zone, multi setpoint control. If the
zones require different pressures for each VAV box, each setpoint may be specified in par. 20-21,
20-22 and 20-23. By selecting
Multi setpoint minimum
, [5], in par. 20-20, Feedback Function, the
PID Controller will increase the speed of the fan if any one of the feedbacks is below its setpoint
and decrease the speed of the fan if all feedbacks are above their individual setpoints.
Sum
[0] sets up the PID Controller to use the sum of Feedback 1, Feedback 2 and Feedback 3 as
the feedback.
NB!
Any unused feedbacks must be set to
No Function
in par. 20-00, 20-03, or 20-06.
The sum of Setpoint 1 and any other references that are enabled (see par. group 3-1*) will be used
as the PID Controller’s setpoint reference.
Difference
[1] sets up the PID Controller to use the difference between Feedback 1 and Feedback
2 as the feedback. Feedback 3 will not be used with this selection. Only setpoint 1 will be used. The
sum of Setpoint 1 and any other references that are enabled (see par. group 3-1*) will be used as
the PID Controller’s setpoint reference.
Average
[2] sets up the PID Controller to use the average of Feedback 1, Feedback 2 and Feedback
3 as the feedback.
NB!
Any unused feedbacks must be set to
No Function
in par. 20-00, 20-03, or 20-06.
The sum of Setpoint 1 and any other references that are enabled (see par. group
3-1*) will be used as the PID Controller’s setpoint reference.
Minimum
[3] sets up the PID Controller to compare Feedback 1, Feedback 2 and Feedback 3 and
use the lowest value as the feedback.
NB!
Any unused feedbacks must be set to
No Function
in par. 20-00, 20-03, or 20-06.
Only setpoint 1 will be used. The sum of Setpoint 1 and any other references that
are enabled (see par. group 3-1*) will be used as the PID Controller’s setpoint
reference.
Maximum
[4] sets up the PID Controller to compare Feedback 1, Feedback 2 and Feedback 3 and
use the highest value as the feedback.
NB!
Any unused feedbacks must be set to
No Function
in par. 20-00, 20-03, or 20-06.
Only Setpoint 1 will be used. The sum of Setpoint 1 and any other references that are enabled (see
par. group 3-1*) will be used as the PID Controller’s setpoint reference.
Multi-setpoint minimum
[5] sets up the PID Controller to calculate the difference between Feedback
1 and Setpoint 1, Feedback 2 and Setpoint 2, and Feedback 3 and Setpoint 3. It will use the feed-
back/setpoint pair in which the feedback is the farthest below its corresponding setpoint reference.
If all feedback signals are above their corresponding setpoints, the PID Controller will use the feed-
back/setpoint pair in which the difference between the feedback and setpoint is the least.
NB!
If only two feedback signals are used, the feedback that is not to be used must
be set to
No Function
in par. 20-00, 20-03 or 20-06. Note that each setpoint
reference will be the sum of its respective parameter value ( 20-12 and 20-13)
and any other references that are enabled (see par. group 3-1*).
Multi-setpoint maximum
[6] sets up the PID Controller to calculate the difference between Feedback
1 and Setpoint 1, Feedback 2 and Setpoint 2, and Feedback 3 and Setpoint 3. It will use the feed-
back/setpoint pair in which the feedback is farthest above its corresponding setpoint reference. If
VLT
p
Automation VT Drive FC322
Programming Guide
2 Parameter Description
MG.20.W1.22 - VLT
p
is a registered Danfoss trademark
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