Danfoss VLT AQUA Drive FC 200 Programming Manual page 135

Parameter Description
20-12 Reference/Feedback Unit
Option: Function:
[0] -
[1] %
[5] PPM
[10] min
[11] RPM
[12] PULSE/s
[20] liter / sec.
[21] liter / min
[22] liter / hr.
[23] m³ / sec.
[24] m³/min
[25] m³ / hr.
[30] kg / sec.
[31] kg/min
[32] kg / hr.
[33] ton / min
[34] ton / hr.
[40] m / sec.
[41] m/min
[45] m
[60] °C
[70] mbar
[71] bar
[72] Pa
[73] kPa
[74] m WG
[75] mm Hg
[80] kW
[120] GPM
[121] gal / sec.
[122] gal/min
[123] gal / hr.
[124] CFM
[125] ft³/s
[126] ft³/min
[127] ft³/h
[130] lbs / sec.
[131] lbs / min.
[132] lbs / hr.
[140] ft/s
[141] ft/min
[145] ft
[160] °F
[170] psi
[171] lb/in²
[172] in. wtr. gage
[173] ft WG
[174] in Hg
[180] HP This parameter determines the unit that is
used for the setpoint reference and feedback
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VLT AQUA Drive Programming Guide
3.17.3 20-2* Feedback & Setpoint
This parameter group is used to determine how the
adjustable frequency drive's PID controller will use the
three possible feedback signals to control the output
frequency of the adjustable frequency drive. This group is
also used to store the three internal setpoint references.
20-20 Feedback Function
This parameter determines how the three possible
feedbacks will be used to control the output frequency of
the adjustable frequency drive.
NOTICE!
Any unused feedback must be set to "No function" in its
Feedback Source 20-00 Feedback 1 Source, 20-03 Feedback 2
Source or 20-06 Feedback 3 Source.
The feedback resulting from the function selected in
20-20 Feedback Function will be used by the PID controller
to control the output frequency of the adjustable
frequency drive. This feedback can also be shown on the
adjustable frequency drive's display, be used to control an
adjustable frequency drive's analog output, and be
transmitted over various serial communication protocols.
The adjustable frequency drive can be configured to
handle multi-zone applications. Two different multi-zone
applications are supported:
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) water
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
Feedback Function, 20-20 Feedback Function to option [3]
Minimum and entering the desired pressure in
20-21 Setpoint 1. The PID controller will increase the speed
of the fan if any one feedback is below the setpoint, and
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MG20O622 - VLT is a registered Danfoss trademark
20-12 Reference/Feedback Unit
Option: Function:
that the PID controller will use for
controlling the output frequency of the
adjustable frequency drive.
•
Multi-zone, single setpoint
•
Multi-zone, multi setpoint
3 3
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