Danfoss FC 100 Series Operating Instructions Manual page 86

How to Programme the Frequ...
20-20 Feedback Function
Option:
[3] Minimum
*
[4] Maximum
7 7
[5] Multi
Setpoint
Min
86
VLT
Function:
Minimum [3] sets up the PID Controller to
compare Feedback 1, Feedback 2 and Feedback 3
and use the lowest value as the feedback.
NOTE
Any unused feedbacks must be set to No
Function in par. 20-00 Feedback 1 Source,
par. 20-03 Feedback 2 Source, or
par. 20-06 Feedback 3 Source. 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.
NOTE
Any unused feedbacks must be set to No
Function in par. 20-00 Feedback 1 Source,
par. 20-03 Feedback 2 Source, or
par. 20-06 Feedback 3 Source.
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 Control-
ler'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 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 will use the feedback/setpoint pair in
which the difference between the feedback and
setpoint is the least.
NOTE
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 Feedback 1 Source,
par. 20-03 Feedback 2 Source or
par. 20-06 Feedback 3 Source. Note that
each setpoint reference will be the sum
of its respective parameter value
(par. 20-21 Setpoint 1, par. 20-22 Setpoint
2 and par. 20-23 Setpoint 3) and any
other references that are enabled (see
par. group 3-1*).
MG.11.AD.02 - VLT
®
HVAC Drive Operating Instructions
20-20 Feedback Function
Option:
[6] Multi
Setpoint
Max
NOTE
Any unused feedback must be set to "No function" in its
Feedback Source parameter: Par. 20-00 Feedback 1
Source, par. 20-03 Feedback 2 Source or
par. 20-06 Feedback 3 Source.
The feedback resulting from the function selected in
par. 20-20 Feedback Function will be used by the PID Controller
to control the output frequency of the frequency converter.
This feedback can also be shown on the frequency converter's
display, be used to control a frequency converter's analog
output, and be transmitted over various serial communication
protocols.
The frequency converter can be configured to handle multi
zone applications. Two different multi zone applications are
supported:
•
Multi zone, single setpoint
•
Multi zone, multi setpoint
The difference between the two is illustrated by the following
examples:
Example 1 – Multi zone, single setpoint
In an office building, a VAV (variable air volume) VLT HVAC
Drive system must ensure a minimum pressure at selected
VAV boxes. Due to the varying pressure losses in each duct,
the pressure at each VAV box cannot be assumed to be the
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is a registered Danfoss trademark
Function:
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 feedback/setpoint pair in which the
feedback is farthest above its corresponding
setpoint reference. If all feedback signals are
below their corresponding setpoints, the PID
Controller will use the feedback/setpoint pair in
which the difference between the feedback and
the setpoint reference is the least.
NOTE
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 Feedback 1 Source,
par. 20-03 Feedback 2 Source or
par. 20-06 Feedback 3 Source. Note that
each setpoint reference will be the sum
of its respective parameter value
(par. 20-21 Setpoint 1, par. 20-22 Setpoint
2 and par. 20-23 Setpoint 3) and any
other references that are enabled (see
parameter group 3-1*).