Danfoss VLT HVAC Drive FC 102 Operating Instructions Manual page 97

How to Programme
20-20 Feedback Function
Option: Function:
NOTICE
If only 2 feedback signals are used, set
the non-used feedback to [0] No Function
in parameter 20-00 Feedback 1 Source,
parameter 20-03 Feedback 2 Source, or
parameter 20-06 Feedback 3 Source. Note
that each setpoint reference is the sum of
its respective parameter value
(parameter 20-21 Setpoint 1,
parameter 20-22 Setpoint 2 and
20-23 Setpoint 3) and any other references
that are enabled (see parameter group
3-1* References).
[6] Multi Sets up the PID controller to calculate the
Setpoint difference between feedback 1 and setpoint 1,
Max feedback 2 and setpoint 2, and feedback 3 and
setpoint 3. It uses 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 uses the feedback/setpoint
pair with the least difference between the 2.
NOTICE
If only 2 feedback signals are used, set
the non-used feedback to [0] No Function
in parameter 20-00 Feedback 1 Source,
parameter 20-03 Feedback 2 Source, or
parameter 20-06 Feedback 3 Source. Note
that each setpoint reference is the sum of
its respective parameter value
(parameter 20-21 Setpoint 1,
parameter 20-22 Setpoint 2 and
20-23 Setpoint 3) and any other references
that are enabled (see parameter group
3-1* References).
MG11F502
Operating Instructions
NOTICE
Set any unused feedback to [0] No function in
Parameter 20-00 Feedback 1 Source,
parameter 20-03 Feedback 2 Source, or
parameter 20-06 Feedback 3 Source.
The PID controller uses the feedback resulting from the
function selected in parameter 20-20 Feedback Function to
control the output frequency of the frequency converter.
This feedback can also:
•
•
•
The frequency converter can be configured to handle
multi-zone applications. 2 different multi-zone applications
are supported:
•
•
Examples 1 and 2 illustrate the difference between the 2:
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 same. The minimum pressure required
is the same for all VAV boxes. This control method can be
set up by setting parameter 20-20 Feedback Function to [3]
Minimum, and entering the desired pressure in
parameter 20-21 Setpoint 1. If any feedback is below the
setpoint, the PID controller increases the fan speed. If all
feedbacks are above the setpoint, the PID controller
decreases the fan speed.
Danfoss A/S © 08/2014 All rights reserved.
Be shown on the frequency converter's display.
Be used to control a frequency converter's analog
output.
Be transmitted over various serial communication
protocols.
Multi-zone, single setpoint
Multi-zone, multi-setpoint
6 6
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