Danfoss VLT Programming Manual page 128

Parameter Description
Damper
Cooling/
heating coil
Damper
Damper
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 20-21 Setpoint 1, 20-22 Setpoint 2 and 20-23 Setpoint 3. By selecting
Multi setpoint minimum, [5], in 20-20 Feedback Function, the PID Controller will increase 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.
20-21 Setpoint 1
Range:
0.000 [-999999.999 -
ProcessCtrlUnit 999999.999
*
ProcessCtrlUnit]
20-22 Setpoint 2
Range:
0.000 [-999999.999 -
ProcessCtrlUnit 999999.999
*
ProcessCtrlUnit]
®
VLT HVAC Drive Programming Guide
Supply
air fan
Return air fan
Function:
Setpoint 1 is used in Closed
Loop Mode to enter a
setpoint reference that is
used by the frequency
converter's PID Controller.
See the description of
20-20 Feedback Function.
NOTE
Setpoint reference
entered here is added to
any other references that
are enabled (see par.
group 3-1*).
Function:
Setpoint 2 is used in Closed
Loop Mode to enter a
setpoint reference that
may be used by the
frequency converter's PID
Controller. See the
description of Feedback
Function, 20-20 Feedback
Function.
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MG.11.CB.02 - VLT is a registered Danfoss trademark
P P
VAV
Box
P P
VAV
Box
P P
VAV
Box
NOTE
The set-point reference entered here is added to any other
references that are enabled (see par. group 3-1*).
20-23 Setpoint 3
Range:
0.000 [-999999.999 -
ProcessCtrlUnit 999999.999
*
ProcessCtrlUnit]
3.18.3 20-3* Feedback Adv. Conversion
In air conditioning compressor applications it is often useful
to control the system based on the temperature of the
refrigerant. However, it is generally more convenient to
directly measure its pressure. This parameter group allows
the frequency converter's PID Controller to convert
refrigerant pressure measurements into temperature values.
Zone 1
Zone 2
Zone 3
Function:
Setpoint 3 is used in Closed
Loop Mode to enter a
setpoint reference that may
be used by the frequency
converter's PID Controller.
See the description of
20-20 Feedback Function.
NOTE
The setpoint reference
entered here is added to
any other references that
are enabled (see
parameter group 3-1*).
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