Danfoss VLT AQUA Drive FC 202 Programming Manual page 139

Parameter Description
Damper
Cooling/
heating coil
Damper
Damper
Illustration 3.52 Multi-zone Application Scheme
Example 2 – Multi-zone, multi setpoint
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 parameter 20-21 Setpoint 1,
parameter 20-22 Setpoint 2 and 20-23 Setpoint 3. By
selecting [5] Multi setpoint minimum in
parameter 20-20 Feedback Function, the PID Controller
increases 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.
20-20 Feedback Function
Option: Function:
[0] Sum Sets up the PID Controller to use the sum of
Feedback 1, Feedback 2 and Feedback 3 as the
feedback.
The sum of Setpoint 1 and any other references
that are enabled (see parameter group 3-1*
References) is used as the PID Controller's
setpoint reference.
[1] Difference Sets up the PID Controller to use the difference
between Feedback 1 and Feedback 2 as the
feedback. Feedback 3 is not used with this
selection. Only setpoint 1 is used. The sum of
Setpoint 1 and any other references that are
enabled (see parameter group 3-1* References) is
used as the PID Controller's setpoint reference.
[2] Average Sets up the PID Controller to use the average of
Feedback 1, Feedback 2 and Feedback 3 as the
feedback.
[3] Minimum Sets up the PID Controller to compare Feedback
1, Feedback 2 and Feedback 3 and use the
MG20O702
Programming Guide
Supply
air fan
Return air fan
Danfoss A/S © Rev. 2014-01-21 All rights reserved.
P P
VAV
Box
P P
VAV
Box
P P
VAV
Box
20-20 Feedback Function
Option: Function:
lowest value as the feedback. Only setpoint 1 is
used. The sum of Setpoint 1 and any other
references that are enabled (see parameter
group 3-1* References) is used as the PID
Controller's setpoint reference.
[4] Maximum Sets up the PID Controller to compare Feedback
1, Feedback 2 and Feedback 3 and use the
highest value as the feedback.
Only Setpoint 1 is used. The sum of Setpoint 1
and any other references that are enabled (see
parameter group 3-1* References) is used as the
PID Controller's setpoint reference.
[5] Multi Sets up the PID Controller to calculate the
Setpoint difference between Feedback 1 and Setpoint 1,
Min Feedback 2 and Setpoint 2, and Feedback 3 and
Setpoint 3. It uses the feedback/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 uses the feedback/setpoint
pair in which the difference between the
feedback and setpoint is the least.
Zone 1
Zone 2
Zone 3
137
3 3