Danfoss VLT FC 102 Operating Instructions Manual page 111

VLT HVAC Low Harmonic Drive Operating In-
structions
NB!
If a feedback is not used, its source must be set to
feedbacks will be used by the PID Controller.
20-01 Feedback 1 Conversion
Option:
[0] * Linear
[1] Square root
[2] Pressure to temperature
[3] Pressure to flow
[4] Velocity to flow
20-03 Feedback 2 Source
Option:
[0] * No function
[1] Analog input 53
[2] Analog input 54
[3] Pulse input 29
[4] Pulse input 33
[7] Analog input X30/11
[8] Analog input X30/12
[9] Analog Input X42/1
[10] Analog Input X42/3
[11] Analog Input X42/5
[100] Bus feedback 1
[101] Bus feedback 2
[102] Bus feedback 3
No Function [0]. Par. 20-20 Feedback Function determines how the three possible
Function:
This parameter allows a conversion function to be applied to Feedback 1.
Linear [0] has no effect on the feedback.
Square root [1] is commonly used when a pressure sensor is used to provide flow feedback
flow ∝ pressure )).
((
Pressure to temperature [2] is used in compressor applications to provide temperature feedback
using a pressure sensor. The temperature of the refrigerant is calculated using the following for-
mula:
A 2
Temperature =
( ln ( Pe + 1 ) − A 1 )
stants. The refrigerant must be selected in par. 20-30
par. 20-23 Setpoint 3 allow the values of A1, A2 and A3 to be entered for a refrigerant that is not
Refrigerant .
listed in par. 20-30
Pressure to flow is used in applications where the air flow in a duct is to be controlled. The feedback
signal is represented by a dynamic pressure measurement (pitot tube).
Flow = Duct Area × Dynamic Pressure × Air Density Factor
See also par. 20-34 Duct 1 Area [m2] through par. 20-38 Air Density Factor [%] for setting of duct
area and air density.
Velocity to flow is used in applications where the air flow in a duct is to be controlled. The feedback
signal is represented by an air velocity measurement.
Flow = Duct Area × Air Velocity
See also par. 20-34 Duct 1 Area [m2] through par. 20-37 Duct 2 Area [in2] for setting of duct area.
Function:
Feedback 1 Source for details.
See par. 20-00
®
MG.16.A1.02 - VLT is a registered Danfoss trademark
6 How to Programme the Low Harmonic Drive
− A 3, where A1, A2 and A3 are refrigerant-specific con-
Refrigerant . Par. 20-21 Setpoint 1 through
6
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