Danfoss VLT Programming Manual page 181

®
VLT HVAC Drive Programming Guide
[6] Multi Setpoint Max
NB!
Any unused feedback must be set to "No function" in its Feedback Source parameter: Par. 20-00
Feedback 2 Source
par. 20-03
The feedback resulting from the function selected in par. 20-20
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 same. The minimum pressure required is the same for all VAV
boxes. This control method can be set up by setting par. 20-20
par. 20-21 Setpoint 1 . The PID Controller will increase the speed of the fan if any one feedback is below the setpoint and decrease the speed of the fan
if all feedbacks are above the setpoint.
NB!
If only two feedback signals are used, the feedback that is not to be used must
No Function
be set to
Source
or par. 20-06
be the sum of its respective parameter value (par. 20-21
par. 20-22 Setpoint 2
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
all feedback signals are below their corresponding setpoints, the PID Controller will use the feed-
back/setpoint pair in which the difference between the feedback and the setpoint reference is the
least.
NB!
If only two feedback signals are used, the feedback that is not to be used must
No Function
be set to
Source
or par. 20-06
be the sum of its respective parameter value (par. 20-21
par. 20-22 Setpoint 2
are enabled (see par. group 3-1*).
Feedback 3 Source
or par. 20-06 .
Feedback Function
will be used by the PID Controller to control the output frequency of
Feedback Function
MG.11.C9.02 - VLT ® is a registered Danfoss trademark
3 Parameter Description
Feedback 1 Source
in par. 20-00
Feedback 3 Source
. Note that each setpoint reference will
and par. 20-23 Setpoint 3 ) and any other references that
Feedback 1 Source
in par. 20-00
Feedback 3 Source
. Note that each setpoint reference will
and par. 20-23 Setpoint 3 ) and any other references that
to option [3], Minimum, and entering the desired pressure in
Feedback 2
, par. 20-03
Setpoint 1 ,
3
Feedback 2
, par. 20-03
Setpoint 1 ,
Feedback 1 Source
,
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